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Ruthenium arene complexes with mono-carbonyl analogues of curcumin as pendant or bridging ligands: Synthesis, anti-cancer activity and interaction with quadruplex DNA
Journal of Integrative Agriculture 2026, 25(4): 1488–1500
Available online at ScienceDirect
Journal of Integrative Agriculture
RESEARCH ARTICLE
Increasing fruit weight and altering flavour of pitaya by supplementing
blue light during fruit growth
Qingming Sun1#, Juncheng Li1, Satish Kumar2, Ran Yao3, Honghua Su4#
1
Institute of Fruit Tree Research, Guangdong Academy of Agricultural Sciences/Key Laboratory of South Subtropical Fruit Biology and Genetic Resource
Utilization, Ministry of Agriculture and Rural Affairs/Guangdong Provincial Key Laboratory of Science and Technology Research on Fruit Trees,
Guangzhou 510640, China
2
The New Zealand Institute for Plant & Food Research Limited, Private Bag 1401, Havelock North 4157, New Zealand
3
Institute of Semiconductors, Chinese Academy of Sciences, Beijing 100083, China
4
College of Plant Protection, Yangzhou University, Yangzhou 225009, China
Highlights
● Blue light increased the weight, firmness, and antioxidant activity of pitaya fruit.
● Blue light had minor effects on primary metabolites but more pronounced effects on volatile compounds.
● Supplemental blue light enriched bioactive compounds in the pitaya fruit peel.
● The accumulation of flavor-associated volatile compounds, such as organic acids, esters, and terpenes in the pulp, was
significantly altered.
Abstract
Supplemental light is often used in fruit production, but few studies have been conducted on pitaya. In this study,
supplemental blue light was applied to pitaya for four hours each night in the field from flowering to fruit ripening to examine
changes in peel and pulp physicochemical parameters and metabolites. Blue light treatment significantly increased fruit
weight, improved fruit firmness by increasing pectin content and retarding hemicellulose degradation, and enhanced
antioxidant enzyme activity. Blue light had minor effects on primary metabolites but more pronounced effects on volatiles.
By affecting alanine, aspartate and glutamate metabolism, blue light treatment resulted in significant fruit growth, increased
accumulation of bioactive ingredients in the peel, and significantly altered the accumulation of flavor-associated volatile
compounds, such as organic acids, esters and terpenes in the pulp. Our results provide an important reference for
improving the yield and quality of pitaya production using supplemental light in the field.
Keywords: pitaya, blue light supplementation, fruit weight, fruit quality, primary metabolites, volatiles
1. Introduction
Pitaya (Selenicereus polyrhizus and Selenicereus undatus),
also known as dragon fruit, originated in Latin America
(Fan et al. 2018). It is now widely cultivated in tropical and
subtropical regions worldwide (Matan et al. 2015) due to its
strong vitality, ability to withstand extreme environments,
resistance to pathogens, convenient field management,
and higher economic value (Mizrahi et al. 2002; Nobel and
Barrera 2004). Consumers prefer pitaya not only because
of its decorative appearance and striking colours, but also
because the betacyanins extracted from pitaya have potential
benefits in ameliorating high-fat diet-related diseases (Song
et al. 2016), and due to its rich nutritional values, including
antioxidants, dietary fibre, vitamins, betalains, minerals,
polyphenols, flavonoids, sugars, organic acids, amino acids
and phytalbumin (Wu et al. 2006; Suh et al. 2014; Hua et al.
2018).
In the northern hemisphere, such as in China and Vietnam,
pitaya which blooms from May to October, has been shown
to be a long-day plant (Nerd and Mizrahi 2010; Jiang et al.
2012). To harvest pitaya fruit of high economic value during
the winter or early spring season, when short day conditions
Received 4 January 2025; Received in revised form 14 May 2025; Accepted 25 September 2025; Available online 24 November 2025
#
Correspondence Qingming Sun, Tel: +86-20-38765789, E-mail: sunqingming@gdaas.cn; Honghua Su, Tel: +86-514-87979344, E-mail: susugj@126.com
© 2026 CAAS. Publishing services by Elsevier B.V. on behalf of KeAi Communications Co. Ltd. This is an open access article under the CC BY-NC-ND
license (http://creativecommons.org/licenses/by-nc-nd/4.0/). Peer review under responsibility of Editorial Board of Journal of Integrative Agriculture.
doi: 10.1016/j.jia.2025.11.034
Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
prevail, additional night lighting is required to induce flowering
(Jiang et al. 2012). Therefore, supplemental lighting is a
useful and proven technology for farmers to induce flowering
and produce pitaya fruit during short day seasons (Xiong
et al. 2020). In addition, light and temperature affect the color
and betalain content of the pitaya peel (Cejudo-Bastante
et al. 2016). Whether it is possible to regulate fruit weight
and quality by light supplementation in the field is a question
worthy of further investigation.
Light is not only an energy source for plants, but also an
essential signal for plant growth and development (Terzaghi
and Cashmore 1995; Nagy and Schäfer 2022). Light can
activate various biological activities in plants when it is
perceived and processed by complicated photoreceptors
(Galvão and Fankhauser 2015), leading to significant
changes in the contents of primary metabolites and volatile
compounds, eventually influencing fruit maturation and
resistance against biotic stresses (Escobar-Bravo et al. 2018).
However, different light qualities play different roles in plants.
For example, the red light promoted rind color development,
β-cryptoxanthin concentration and gene expression pattern
related to the accumulation of β-cryptoxanthin and lutein of
citrus fruit (Ma et al. 2012, 2015; Yamaga et al. 2016). An
artificial light source with UV-B was reported to increase
the phenolic compounds and antioxidant activity in Pak
choi (Brassica rapa ssp. chinensis) and Swiss chard (Beta
vulgaris subsp. vulgaris) (Wessler et al. 2025). Supplemental
greenhouse lighting strongly enhanced photosynthesis
and plant growth while increasing water use efficiency in
Cannabis sativa (Collado et al. 2024). In tomato and rice
(Oryza sativa), blue light treatment showed greater induction
and higher steady-state non-photochemical quenching
(Hamdani et al. 2019; Zhang et al. 2019). Supplemental blue/
red lighting accelerated fruit coloring and promoted lycopene
synthesis in tomato, resulting in enhanced fruit coloring (Wang
et al. 2021). Acclimation to supplemental blue light can
improve light use efficiency and reduce photoinhibition under
high solar light exposure, benefiting plant growth in cucumber
(Kang et al. 2021). Supplemental blue light treatment
improved flowering and ripening process and nutritional
qualities of tomato fruits, and significantly enhanced lycopene
content, total phenolic compounds, total flavonoids, vitamin C,
and soluble sugar (He et al. 2022). The response to blue light
could trigger the biosynthesis of primary metabolites, amino
acids and secondary metabolites in tomato fruit (Xiao et al.
2022). Blue light treatment can also effectively delay the
decay of many fruits during postharvest storage. The decay
of pitaya fruit was significantly delayed by 300 lx blue light for
2 h, and changes in several physiological characteristics of
pitaya fruit were also significantly reduced (Wu et al. 2020b)
Metabolites change significantly during fruit development
and senescence (Li J et al. 2017; Hua et al. 2018). With
the development of detection technologies, high-throughput
methods now provide large datasets for detecting the
accumulation and fluctuation of metabolites and nutrients
(Ikeda et al. 2016; Feng et al. 2017). A previous study
indicated that starch, organic acids and inositol decreased,
while glucose, fructose, sucrose and sorbitol increased
markedly during fruit ripening (Hua et al. 2018). In
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recent years, more valuable research focusing on pitaya
metabolomics has been reported. The contents and changes
in sugars, aldehydes, free amino acids and alkanes may
influence pulp quality and the biotic resistance of dragon
fruit (Wu Q et al. 2023). Essential fatty acids are abundant
in pitaya seeds, and the seed oil extracts contain about 50%
essential fatty acids (C18:2 and C18:3) (Ariffin et al. 2009).
Aside from its nutritional properties, previous research has
found that pitaya fruit is a valuable antioxidant due to its
polyphenol content (Wu et al. 2006).
We have previously used different single wavelength LED
light sources, including 730, 660, 590, 520 and 450 nm,
to supplement light to pitaya for 4 hours per night in field
production and found that blue 450 nm light was effective in
significantly increasing single fruit weight and fruit firmness,
and in extending post-harvest freshness (unpublished
data). Therefore, this study aimed to investigate the effect
of supplemental blue LED light during the fruit development
period on physiological parameters, primary metabolites
and volatile compounds in pitaya peel and pulp, and to
provide a theoretical basis and method for efficient light
supplementation in pitaya cultivation and fruit quality
improvement.
2. Materials and methods
2.1. Plant materials and treatments
Three-year-old red flesh pitaya ‘Dahong’ (Selenicereus
polyrhizus) plants from a commercial plantation in
Guangzhou, central Guangdong Province, China (23°57´N,
113°55´E), were used in this study.
Blue light treatment was applied from the day of flowering
until fruit ripening, which occurred from June 25 to July 30,
2022. The plants were provided with additional light for four
hours per night from 18:30 to 22:30 using LED lights with a
wavelength of 450 nm, at 15 W.
The lights were placed 50 cm above the plants at 1.0 m
intervals and the plant canopy received 20 µmol m –2 s –1
PPFD. The control plants received no additional light.
At 25, 30 and 35 days after anthesis (DAA), 30 individual
fruits were randomly selected at a distance of 50 to 60
centimetres from the canopy. Each sample was randomly
divided into three replicates (10 fruits per replicate) for the
subsequent experiments. After basic index measurements,
peel and pulp samples were immediately collected in liquid
nitrogen and stored at –80°C for further physiological
parameter analysis and metabolomic analysis.
2.2. Determination of physiological indices in the pitaya peel
Fruit firmness was determined by using a penetrometer
(GY-4, Beijing Jinke Lida Company, China) according to the
manufacturer’s instructions. The a*, b* and L* values were
measured directly in the middle of the light-facing side of the
peel using a SP-60 colour meter (X-Rite Inc., Grand Rapids,
MI, USA). Measurements were taken on 30 fruits and
averaged for comparison purposes. The a* value indicates
the degree of reddish-yellow colour of the peel; the higher
the a* value, the redder the peel. The b* value indicates the
degree of yellow and blue in the peel; the higher the b* value,
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Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
the greater the degree of yellow bias in the peel. The L*
value indicates the brightness of the peel; the higher the L*
value, the brighter the peel.
Hemicellulose and total pectin contents were measured
according to the manufacturer’s instructions for the test kits
(D799023-0100 and D799294-0100, Sangon Biotech Co.,
Ltd., Shanghai, China). Cellulose content was measured
using the test kit (BC4285, Solarbio Science & Technology
Co., Ltd., Beijing, China), following the manufacturer’s
instructions.
The content of betacyanin was measured as described by
Hua et al. (2018). A total of 2 g of pulp or peel powder ground
with liquid nitrogen, was weighed and made up to 20 mL
with 80% methanol, extracted by ultrasound for 10 min, and
then extracted by oscillation in the dark for 20 min. This was
centrifuged at 5,000 r min–1 for 10 min at room temperature,
then 1 mL of the supernatant was diluted four times, and light
absorbance at 538 nm was determined. The formula used
was:
Betacyanin content (mg 100 g–1 FW) =(A538×MW×V×DF×
100)/(E×L×m)
where A 538 is the light absorption value of the diluent at
538 nm; V is the volume of the extracted liquid (mL); DF
is the dilution ratio; E is the molar absorption coefficient
of betacyanin, which is 65,000 L mol –1 cm –1; MW is the
molecular weight of betacyanin, which is 550 g mol–1; L is the
optical path length, which is 1.0 cm; and m is the fresh weight
of samples (g).
The activities of catalase (CAT), peroxidase (POD) and
superoxide dismutase (SOD) were measured following the
manufacturer’s instructions for the test kits (D799592-0100,
D799598-0100 and D799594-0100, Sangon Biotech Co.,
Ltd., Shanghai, China). The DPPH free radical scavenging
ability, hydroxyl radical scavenging ability, and flavonoid
content were measured as described in the manufacturer’s
instructions for the test kits (D799295-0100, D799276-0100
and D799280-0100, Sangon Biotech Co., Ltd., Shanghai,
China). For all physiological index determinations of the
pitaya peel, three replicates were measured.
2.3. Determination of physiological indices in the pitaya
pulp
The total sugar content was measured as described in
the manufacturer’s instructions for the test kit (D7991670100, Sangon Biotech Co., Ltd., Shanghai, China). The
reducing sugar content was measured as described in the
manufacturer’s instructions for the test kit (D799394-0100,
Sangon Biotech Co., Ltd., Shanghai, China). The amino acid
content was measured as described in the manufacturer’s
instructions for the test kit (D799584-0100, Sangon Biotech
Co., Ltd., Shanghai, China). Protein contents were measured
according to the method described by Elfalleh et al. (2009).
Three replicates were measured for all physiological index
determinations of the pitaya pulp.
2.4. Profiling of primary metabolites
Primary metabolomic profiling was based on the method
described by Zhu et al. (2015), with minor modifications.
A 200 mg sample was added to 1,800 μL of methanol
(–20°C) for extraction, and 200 μL of 0.2 mg mL–1 ribitol in
water was used as an internal standard for quantification.
The extracts were incubated with ultrasound treatments
at 4°C and heated at 70°C with a water bath for 15 min.
After 0.5 h in a refrigerator at –20°C, the extracts were
centrifuged at 5,000 g for 15 min at 4°C. Then 100 μL of the
supernatant was collected for the derivatization reaction. The
derivatization reaction was first incubated in 80 μL of 20 mg
mL–1 methoxyamine hydrochloride in pyridine for 1.5 h at
37°C, and then 80 μL of MSTFA [N-Methyl-N-(trimethylsilyl)
trifluoroacetamide] was added at 37°C for 0.5 h.
A volume of 1 μL of the sample was used for analysis
using a gas chromatography-mass spectrometry (GCMS) system (GCMS-QP2010 Plus, Shimadzu Corporation,
Kyoto, Japan) with the DB-5ms fused-silica capillary
stationary phase column (30 m×0.25 mm ID, 0.25 μm, Agilent
Technologies Inc., California, USA). The injector temperature
was 250°C, and the carrier gas (99.999% helium) flow rate
was 1.2 mL min–1. The column temperature was initially held
at 100°C for 1 min, then increased to 184°C at 3°C min–1,
further increased to 190°C at 0.5°C min–1 and held for 1 min,
and finally increased to 280°C at 15°C min–1 for 5 min. The
interface temperature was 250°C, and the ionization voltage
of the MS was 70 eV. The spill ratio was 10:1, and the total
ion current (TIC) spectra were scanned in the range of 45–
600 m/z.
2.5. Volatile aroma analysis
Each fruit peel (4 g) was ground and homogenized with 4 mL
of saturated sodium chloride solution. A total of 10 μL of
0.2 mg mL–1 ribitol in water was used as an internal standard
for quantification. The extracts were then placed at 40°C
for 15 min before collecting the aromatic compounds. The
aromatic compounds were collected for 45 min using the
method described by Jing et al. (2015).
GC-MS analysis was carried out following the method
described by Jing et al. (2015). A GC-2010 gas chromatograph
(Shimadzu, Suzhou, China) equipped with a GCMS-QP2010
Plus mass spectrometer (Shimadzu, Suzhou, China) was
used. Volatile separation was performed using a 30 m Rxi5ms capillary column (0.25 mm ID) with a split/ splitless
injector. Samples were loaded into the injector, and three
replicates of each sample were analyzed. The amount of
each volatile compound was determined based on the ratio of
the peak area of the target compound to the peak area of the
internal standard, which was cyclohexanone.
2.6. Gene expression
Total RNA was extracted from pitaya peel and pulp tissues
using a Plant RNA Kit (R6827-01, Omega Biotek, USA)
according to the manufacturer’s instructions. RNA was
treated with the PrimeScript RT Reagent Kit (RR037A,
TaKaRa, Japan) for RNA reverse transcription. The primers
were designed for the 28 target genes and one reference
gene in Appendix A and quantitative RT-PCR, transcription
normalization, and relative quantification were performed as
previously described using three biological replicates with the
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Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
vs. 263.33 g) and 35 DAA (301.67 g vs. 354.33 g) (Fig. 1-B;
Appendix B) . The average peel weight gradually decreased
with fruit development. At 25 and 30 DAA, the peel weight
of the blue light treatment group was lower than that of the
control group (Fig. 1-D). However, at 35 DAA, the peel
weight of the blue light treatment group ((88.67±1.86) g) was
slightly higher than that of the control group ((77.67±8.09)
g). The firmness of the fruit under blue light treatment was
significantly higher than the control group (Fig. 1-E). The a*
and b* values of the peel in the control group were slightly
higher than those in the blue light group (Fig. 1-F), indicating
that the peel in the control group was more skewed towards
red and yellow and more ripe. Therefore, blue light delayed
fruit ripening.
Further analysis showed that the average fruit weight
of the control group increased by 21% from 25 to 30 DAA,
while a 19% increase was observed from 30 to 35 DAA.
For the same periods, the average fruit weight increased by
33 and 34.56%, respectively, under the blue light treatment
(Appendix B). The blue light treatment resulted in significantly
higher fruit weight than the control during the later stages (i.e.,
25 and 35 DAA) of the fruit development, suggesting that the
main stage at which blue light promotes an increase in fruit
weight is between 25 and 35 DAA.
Between 25 and 30 DAA, the average peel weight
decreased by 21.26 and 20.85% in the control and blue
light treatments, respectively, while the average pulp weight
increased by 128.57 and 166.67%, respectively. Similarly,
between 30 and 35 DAA, the peel weight decreased by
35.81 and 20.36% in the control and blue light treatments,
2.7. Statistical analysis
The experiments were designed as completely randomized,
and the results were expressed as the mean values of three
biological replicates. The mean±standard error (SE) was
calculated for each set of biological replicates. Data analysis
was performed using SPSS version 16.0. One-way analysis
of variance (ANOVA) was performed, followed with Tukey
significant difference test at an alpha level of 0.05.
Data analysis of primary metabolites and volatile aromas
included PLS-DA and KEGG pathway analysis. Partial least
squares-discriminant analyses (PLS-DA) were conducted
using SIMCA version 13.0 to investigate variety-specific
accumulation of metabolites. The thresholds for statistical
significance were a p-value of 0.05 and a fold-change of 2.0,
respectively. KEGG pathway analyses were conducted using
MetaboAnalyst 5.0 (https://www.metaboanalyst.ca/).
3. Results
3.1. Effects of blue light treatment on pitaya fruit
weight and firmness
The visual appearances of pitaya fruit from the control and
blue light groups are shown in Fig. 1-A. Fruit weight and
pulp weight showed an increasing trend during fruit growth
and development (Fig. 1-B and C). The average fruit weight
of the control group was slightly higher than that of the blue
light treatment group at 25 DAA (214.33 g vs. 197.67 g),
but the supplemental blue light treatment resulted in higher
average fruit weight compared to the control at 30 (259.67 g
A
25 DAA
B
35 DAA
30 DAA
1 cm
1 cm
Weights of fruit (g)
1 cm
Control
1 cm
1 cm
1 cm
CK
Blue light
C
500
a
400
300
c
cd d
200
c
a
b
c
d
q00
0
c
d
35
25
30
Days after anthesis (DAA)
35
25
30
Days after anthesis (DAA)
Blue
300
b
200
100
Weights of pulp (g)
SYBR Premix Ex Taq Kit (RR420A, TaKaRa, Japan).
0
light
CK
150
100
F
a
a
b
b
c
c
40
d
d
20
50
0
60
35
25
30
Days after anthesis (DAA)
Peel
0
60
50
Chroma value
200
Blue light
E
250
Hardness of fruit (N)
Weights of peel (g)
D
ns
ns
40
30
20
ns
10
0
L*
a*
b*
Fig. 1 Physical and chemical indices of pitaya fruit after blue light treatment. A, change in visual appearance of pitaya fruit. Scale
bar=1 cm. B, the weights of fruit. C, the weights of pulp. D, the weights of peel. E, the hardness of fruit. F, the chroma value of peel.
Data are presented as the mean±SE (n=3). Different letters indicate significant (P<0.05) differences between means by ANOVA combined
with Duncan’s multiple range test, and ns indicates non-significant difference (P>0.05).
Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
3.3. Effect of blue light treatment on the physicochemical
parameters of the pitaya pulp
Compared to the control, the blue light treatment increased the
contents of total sugar and reducing sugar in the pulp at 25
and 30 DAA (Fig. 3-A and B). The content of total sugar in the
25
a
b
150
d
100
b
c
d
cd
b
a
20
a
b
10
5
50
0
80
15
25
30
35
Days after anthesis (DAA)
C
a
a
60
b
ab
25
30
35
Days after anthesis (DAA)
D
20
ns
ns
15
b
b
0
40
10
20
5
0
25
30
35
Days after anthesis (DAA)
Peel
Blue light
CK
1,000
E
a
a
0
Pulp
50
F
40
800
a
600
b
400
c
200
0
4,000
c
c
G
c
d
c
a
b
80
60
40
20
c
0
J
c
0
e
I
150
50
0
a
c
1,000
10
a
ab
30
20
c
d
b
2,000
100
b
H
3,000
0
c
a
a
6
b
b
d
f
a
c
e
d
25
30
35
Days after anthesis (DAA)
DPPH free radical
scavenging ability (%)
a
200
Contents of betacyanin
(mg 100 g–1 FW)
250
Contents of cellulose
(mg g–1)
30
B
Hydroxyl radical
scavenging ability (%)
A
d
d
25
30
35
Days after anthesis (DAA)
4
2
Contents of
flavonoid (mg g–1 FW)
Contents of hemicellulose
(mg g–1 DW)
300
100
Contents of total pectin
(mg g–1)
Compared to the control group, the blue light treatment
resulted in higher levels of hemicellulose in the peel (Fig. 2-A).
During the fruit development period from 25 to 35 DAA,
hemicellulose content degraded more slowly in the blue light
treatment compared to the control.
The peel pectin content was significantly different,
especially at 35 DAA, between the blue light treatment
((71.05±7.63) μmol g–1) and the control ((51.63±2.2) μmol
g–1) (Fig. 2-C). Compared with the control group, blue light
treatment decreased cellulose content (Fig. 2-B). The
primary plant cell wall is composed of a complex network
of pectin, hemicellulose and cellulose. Blue light treatment
retarded hemicellulose degradation, maintained high pectin
levels, and slightly affected cellulose, thereby reducing cell
wall degradation compared to the control group. There was
no significant difference in pulp and peel betacyanin content
between the two treatments (Fig. 2-D). These results showed
that blue light treatment delayed fruit ripening and increased
fruit firmness, mainly by decreasing the hemicellulose
degradation rate and promoting the accumulation of pectin in
the pericarp.
The activities of CAT (Fig. 2-E) increased gradually
during fruit growth, but there was no significant difference
between the blue light treatment and the control group at
35 DAA. The blue light treatment increased POD activity
(Fig. 2-G), especially at 35 DAA; the POD activity of the
blue light-treated group was significantly higher than that
of the control group. Unlike the patterns of CAT and POD,
SOD activities decreased gradually during fruit growth, but
blue light treatment significantly enhanced SOD activities
(Fig. 2-I) compared with the control group. During the fruit
development period, flavonoid contents (Fig. 2-J) increased
in both groups. Compared with the control group, blue light
treatment significantly increased flavonoid content in the fruit
peel, especially at 35 DAA, when the flavonoid contents in
the control group and the blue light treatment group were 3.25
and 4.18 mg g–1 FW, respectively. Due to significant changes
in the activities of CAT, POD, SOD, and flavonoid contents
under blue light treatment, free radical scavenging ability
may have been enhanced. Compared with the control group,
the hydroxyl radical scavenging ability (Fig. 2-H) increased
after blue light treatment, with significant changes observed
between 25 and 35 DAA, while DPPH free radical scavenging
ability (Fig. 2-F) was similar at maturity.
Activities of CAT
(U g–1 FW)
3.2. Effect of blue light treatment on the physicochemical
parameters of the pitaya peel
Blue light
CK
Activities of POD
(U g–1 FW)
respectively (Appendix B), while the average pulp weight
increased by 61.54 and 74.78%, respectively. Therefore,
in the later stages of fruit development (25 to 35 DAA), the
blue light treatment helped increase pulp weight, leading to a
significant increase in overall fruit weight.
Activities of SOD
(U g–1 FW)
1492
0
Fig. 2 Physical and chemical indices of pitaya peel after blue
light treatment. A–D, contents of hemicellulose (A), cellulose
(B), pectin (C), and betacyanin (D). E, G and I, activities of CAT
(E), POD (G) and SOD (I). F, DPPH free radical scavenging
ability. H, hydroxyl free radical scavenging ability. J, contents of
flavonoid. Data are presented as the mean±SE (n=3). Different
letters indicate significant (P<0.05) differences between means by
ANOVA combined with Duncan’s multiple range test.
blue light treatment group at 25 and 30 DAA was (83.01±6.29)
and (82.35±2.88) mg g–1, respectively (Fig. 3-A). Blue light
treatment significantly increased the content of reducing
sugar especially at 30 DAA, reaching (4.81±0.16) mg g–1;
both sugars increased gradually and reached the same level
at 35 DAA. The content of total amino acids in the pulp
decreased gradually from 25 to 35 DAA (Fig. 3-C), reaching
(67.38±3.37) μmol g–1 FW at 35 DAA in the blue light group,
which was markedly greater than that in the control group
(Fig. 3-C). These results suggest that blue light treatment
can improve fruit quality and nutritional value of pitaya fruit.
During the fruit development period, the contents of total
protein (Fig. 3-D) in the blue light-treated group were higher
100
80
B
CK
Blue light
a
a
a
8
a
a
b
c
a
6
b
d
d
c
4
60
40
Contents of amino acids
(μmol g–1 FW)
A
120
100
80
60
40
2
C
0
D
a
a
0.3
a
a
ab
b
c
b ab
b
a
0.1
c
25
30
35
Days after anthesis (DAA)
0.2
25
30
35
Days after anthesis (DAA)
Contents of protein
(mg mL–1)
Contents of total sugar
(mg g–1)
120
Contents of reducing sugar
(mg g–1)
Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
0.0
Fig. 3 Physical and chemical indices of pitaya pulp after blue
light treatment. A–D, contents of total sugar (A), reducing sugar
(B), amino acids (C), and protein (D). Data are presented as the
mean±SE (n=3). Different letters indicate significant (P<0.05)
differences between means by ANOVA combined with Duncan’s
multiple range test.
than that in the control group. It can be inferred that blue light
treatment promoted the accumulation of sugars, amino acids
and proteins in the pulp to a certain extent, thereby improving
fruit quality.
3.4. Comparative analyses of primary metabolites in
the peel and pulp of pitaya fruit
The primary metabolites and volatile components were
analyzed from the peel and pulp of pitaya in the blue light
treatment group and the control group. Based on the
categories and total content of metabolites (Fig. 4-A and B),
significant differences were found between the peel and pulp.
A total of 272 primary metabolites were detected and divided
into 7 different categories, including 63 acids, 15 alcohols,
29 amino acids, 23 esters, 26 sugar alcohols, 52 sugars and
64 others. Acids (52), sugars (40), sugar alcohols (24) and
esters (22) were more abundant in the peel than in the pulp,
where the numbers of compounds in these categories were
45, 31, 16 and 11, respectively.
The content of primary metabolites in the pulp was greater
than that in the peel, except for ester compounds (Fig. 4-B).
Blue light treatment had a minor effect on primary metabolites
in the peel and pulp (Fig. 4-E and F).
3.5. Comparative analyses of volatile components in
the peel and pulp of pitaya fruit
A total of 234 volatile components were detected. Details
of the categories of volatile components and their relative
concentrations are shown in Fig. 4-C and D. There were nine
categories of volatile components, including acids, alcohols,
aldehydes, alkanes, esters, heterocyclic compounds,
ketones, terpenes and others. Except for acids, other volatile
components were more frequently found in the peel than in
the pulp. The peel was rich in alcohols, aldehydes, esters
and ketones, while the pulp was rich in aldehydes, alcohols
and acids.
Volatiles from the peel showed different trends during fruit
1493
development. As shown in the Fig. 4-G, from 25 to 35 DAA,
the contents of alkanes and ketones increased; acids and
aldehydes decreased; and alcohols, esters, heterocyclic
compounds, and terpenes showed an increasing and then
decreasing trend in both the control group and in the bluelight-treated group. Compared with the control group, under
blue light treatment the levels of esters, alcohols, and ketones
decreased, while the levels of acids, alkanes, and aldehydes
increased. In the later stages of development (30 to 35 DAA),
aldehydes and ketones increased significantly, and alcohols
decreased rapidly.
During fruit development, volatiles from the pulp (Fig. 4-H)
showed that acids, ketones, terpenes and esters increased;
aldehyde content decreased; and ketones increased
rapidly as the fruit color changed between 30 and 35 DAA.
Supplemental blue light led to an increase in acid, ester and
terpene content during fruit development, an increase in
alcohol content, and a significant decrease in aldehydes at
the ripening stage (30 to 35 DAA). This could be attributed to
the changes in fruit flavor due to the accelerated conversion
of aldehydes to acids, alkanes, esters, and terpenes caused
by blue light, but there was no effect on ketone content at the
final stage (35 DAA).
3.6. Differentially accumulated metabolites in the peel
in response to the blue light treatment
PLS-DA analysis was carried out on the peel metabolomics
data (Fig. 5-A). The blue-light-treated group was mainly
distributed in the third quadrant, while the control group
was discretely distributed in the first, second and fourth
quadrants, indicating that the metabolites differed greatly
between the control and blue light-treated groups during peel
development.
A total of 22 differential metabolites (Fig. 5-C) were detected
in the peel between the blue light treatment and the control.
These included acids (10), sugar alcohols (5), alcohols (2),
sugars (1), aldehydes (1), esters (1), and others (2).
With blue light treatment, the content of most differential
metabolites in the peel (Fig. 5-C) increased significantly,
except for (E)-2-hexen-1-ol. Compared with the control
group, (E)-2-hexen-1-ol decreased markedly after blue
light treatment from 25 to 35 DAA, while in the control
group, it increased gradually. (E)-2-Octenal was a uniquely
differentially accumulated aldehyde in this study. During
fruit development, its levels tended to decrease in both the
control and blue light treatment groups, however most of the
other differential metabolites from the peel were gradually
accumulated (Fig. 5-C). Between 25 and 30 DAA, the
content of (E)-2-Octenal decreased significantly, and the rate
of decline slowed from 30 to 35 DAA. However, supplemental
blue light significantly increased the amount of (E)-2octenal accumulated at various stages of peel development
from 25 to 35 DAA. At day 30 of fruit development, the
accumulation of eight metabolites was significantly promoted
by blue light, including three acids: 2,3,5,6-tetrahydroxy-4[3,4,5-trihydroxy-6-(hydroxymethyl) oxan-2-yl] oxyhexanoic
acid, (+)-pantothenic acid and vanillic acid; one alcohol:
2,5,7,8-tetramethyl-2-(5,9,13-trimethyltetradecyl)-3,4-dihydro-
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A
B
Acids
Alcohols
Others
Peel
Pulp
Acids
Alcohols
Amino acids
Esters
Amino acids
Sugars
Peel
Sugar alcohols
Pulp
Sugars
Others
C
0
Esters
Sugar alcohols
Content (μg g–1)
D
Acids
Alcohols
Others
Aldehydes
Terpenes
Peel
Ketones
Alkanes
0
Esters
Acids
Sugars
Others
Esters
Sugar alcohols
Amino acids
Alcohols
1
0.9
Proportion
0.8
0.7
0.6
Others
Acids
Sugars
Amino acids
Sugar alcohols
Alcohols
Esters
0.7
0.6
0.5
0.3
0.2
0.2
0.1
0.1
0
CK B
25 DAA
CK B
35 DAA
CK B
30 DAA
CK B
35 DAA
H
0.5
Aldehydes
1
Alcohols
Esters
0.9
Ketones
0.8
Alkanes
Others
Heterocyclic compounds 0.7
Acids
0.6
Terpenes
0.5
0.4
0.4
0.9
0.8
Proportion
0.7
0.6
0.3
0.3
0.2
0.2
0.1
0.1
0
100
0.8
0.3
CK
B
30 DAA
40
60 80
Content (μL g–1)
1
0.4
CK B
25 DAA
20
0.9
0.4
1
Proportion
F
0.5
0
G
Ketones
Terpenes
Others
Proportion
E
Peel
Pulp
Acids
Alcohols
Aldehydes
Alkanes
Esters
Heterocyclic compounds
Pulp
Heterocyclis compounds
5,000 10,000 15,000 20,000
CK B
25 DAA
CK B
30 DAA
CK B
35 DAA
0
Aldehydes
Alcohols
Acids
Alkanes
Terpenes
Esters
Ketones
Others
Heterocyclic compounds
CK B
25 DAA
CK B
30 DAA
CK B
35 DAA
Fig. 4 Data analyses of metabolomics of pitaya peel and pulp. A, distribution of various primary metabolites in peel and pulp of pitaya
fruit. B, total concentrations of different primary metabolites in peel and pulp of pitaya fruit. C, distribution of various volatile compounds
in peel and pulp of pitaya fruit. D, total concentrations of different volatile compounds in peel and pulp of pitaya fruit. E, percentage of
primary metabolities in peel from control (CK) and blue light (B) treatment. F, percentage of primary metabolities in pulp from CK and B.
G, percentage of volatile compounds in peel from CK and B. H, percentage of volatile compounds in pulp from CK and B. DAA, days
after anthesis.
2H-chromen-6-ol); one aldehyde (E)-2-octenal, one ester
arachidonate, 1,5-anhydro-D-glucitol and alpha-D-mannose
1-phosphate. At 35 DAA, five important volatile compounds
including three acids, (9Z,12Z,15Z)-octadecatrienoic acid,
vanillic acid, and pipecolic acid, one aldehyde (E)-2-octenal;
and one compound benzene-1,2,4-triol, were enhanced after
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blue light treatment.
The accumulation of bioactive ingredients in the peel
was significantly promoted by blue light treatment. The
contents of DL-tartaric acid, 2-oxoglutarate, nicotinic acid,
2-hydroxyglutaric acid, D-glucaric acid, gamma-tocopherol,
1,5-anhydrohexitol, beta-sitosterol, delta-tocopherol and
coniferin were gradually stabilized at 30 and 35 DAA in both
the control and blue-light-treated groups.
Among them, the level of hippuric acid was significantly
increased by blue light treatment at 35 DAA. In contrast, three
acids (2-methylpropanoic acid, linolenic acid, and propanoic
acid) decreased with fruit development, with linolenic acid
being significantly down-regulated by blue light compared to
the control. Except for n-tridecan-1-ol, alcohols and aldehydes
decreased with fruit growth in both groups (Fig. 5-D).
Compared to the control, the levels of 3-methyl-3-buten-1-ol
and 2-ethyl-1-hexanol were slightly decreased by blue light.
Except for 2-propenal, the contents of differential aldehydes
(Fig. 5-D) increased significantly after blue light treatment, with
the most notable change observed in benzeneacetaldehyde
at 35 DAA, which was significantly greater in the blue-lighttreatment group than in the control group. The same pattern
was observed with 2-methylbutanal and 3-methylbutanal.
In addition, blue light treatment promoted the accumulation
of 3-methylfuran, 14-methyloxacyclotetradecan-2-one and
longifolene at 30 DAA and significantly inhibited the production
of lauroyl-L-carnitine in the pulp.
3.7. Differentially accumulated metabolites in the pulp
in response to blue light treatment
The PLS-DA score plot of the pulp metabolites showed
that each treatment group clustered and was distributed
separately (Fig. 5-B), and the difference between groups was
significant. Blue light treatment had a significant effect on
metabolites in the pulp.
A totol of 26 differential metabolites (Fig. 5-D) were
detected in the pulp between the control and blue-lighttreated groups, belonging to eight categories: acids (9),
aldehydes (6), alcohols (5), heterocyclic compounds (1),
alkanes (1), ketones (1), terpenes (1), and others (2).
Six acids (palmitoleic acid, cis-7-hexadecenoic acid,
n-decanoic acid, octanoic acid, pentanoic acid, and hippuric
acid) gradually accumulated with fruit development (Fig. 5-D).
A
The results of KEGG pathway analysis showed that blue light
supplementation significantly affected alanine, aspartate and
B
CK25
CK30
CK35
B25
B30
B35
8
6
4
2
CK25
CK30
CK35
B25
B30
B35
6
4
2
0
t [2]
t [2]
3.8. KEGG pathway analysis of the pitaya fruit
response to blue light treatment
–2
0
–2
–4
–4
–6
–6
–8
–10
–15
–10
–5
R2×[2]=0.11
R2×[1]=0.22
0
t [1]
5
–8
–10
10
Ellipse: Hotelling’s T2 (95%)
C
2,3,5,6-Tetrahydroxy-4-[3,4,5-trihydroxy-6(hydroxymethyl)oxan-2-yl]oxyhexanoic acid
DL-Tartaric acid
(+)-Pantothenic acid
–8
R2×[1]=0.156
–6
0
2
4
6
8
–4
–2
t [1]
R2×[2]=0.0878 Ellipse: Hotelling’s T2 (95%)
D
3.0
Palmitoleic acid
cis-7-Hexadecenoic acid
n-Decanoic acid
Octanoic acid
0.0
Pentanoic acid
Hippuric acid
Linolenic acid
–3.0
Propanoic acid
2-Methyl propanoic acid
(Z)-3,7-dimethyl-2,6-Octadien-1-ol
n-Tridecan-1-ol
*-Methylbenzenemethanol
3-Methyl-3-Buten-1-ol
2-Ethyl-1-Hexanol
Benzeneacetaldehyde
2-Methylbutanal
3-Methylbutanal
Benzaldehyde
2-Propenal
Acetaldehyde
2,2-dimethylundecane
3-Methylfuran
14-Methyloxacyclotetradecan-2-one
Longifolene
Lauroyl-L-carnitine
Methyl 2-hydroxy-4-methylbenzoate
3.0
(9Z,12Z,15Z)-Octadecatrienoic acid
2-Oxoglutarate
Nicotinic acid
2-Hydroxyglutaric acid
0.0
Vanillic acid
Pipecolic acid
D-Glucaric acid
–3.0
(E)-2-Hexen-1-ol
2,5,7,8-Tetramethyl-2-(5,9,13-trimethyltetradecyl)3,4-dihydro-2H-chromen-6-ol
(E)-2-Octenal
Arachidonate
gamma-Tocopherol
1,5-Anhydrohexitol
beta-Sitosterol
delta-Tocopherol
1,5-Anhydro-D-glucitol
alpha-D-Mannose 1-phosphate
Coniferin
25 K25
25
CK
CK C
0/
0/ 35/
3
3
K
B
CK C
/C
K2
25
5/
25
B2
25
B3
5
25
5
C
B3 K2
0/ 5
CK
30
B3
5/
CK
35
Benzene-1,2,4-triol
0
5
K
K
K
K3 K3
K
CK
0/ 35/C 30/C 35/C 5/C 0/C 35/C
3
3
2
B
B
B
B
B
CK CK
25
Fig. 5 PLS-DA score plots and differential metabolites in pitaya peel and pulp after blue light treatment. A and B, PLS-DA score
plot of metabolomics of pitaya peel (A) and pitaya pulp (B). C and D, the differential metabolites in pitaya peel (C) and pitaya pulp (D).
CK25, CK30, and CK35, samples from the control group collected at 25, 30, and 35 days after anthesis, respectively. B25, B30, and B35,
samples from the blue light treatment group at the corresponding time points.
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Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
glutamate metabolism in pitaya fruit (Fig. 6-A). Therefore,
quantitative RT-PCR on related genes in this pathway was
conducted to clarify the mechanism of action (Fig. 6-B).
HuAGT2-1, HuAGT2-2, HuGAD5, HuGSs, HuALT2-2 and
HuALT2-3 were significantly up-regulated in the peel and
showed varying degrees of up-regulation throughout the fruit
A
development stage. HuSSP2, HuAS2, HuGOGAT1-2/1-3,
HuGADs, and HuGSs were significantly upregulated at 25 DAA
compared with the control group, and HuAS2, HuGOGAT1-3
and HuGAD1 were significantly upregulated during fruit
development. The remaining genes were downregulated.
According to KEGG pathway analysis, a metabolic
B
7
HuALT2-1
HuALT2-2
HuALT2-3
HuAGT2-1
HuAGT2-2
HuAGT2-3
HuASN
HuSSP1
HuSSP2
HuSSP3
HuAS1
HuAS2
HuMBD9
HuL-AO
HuGOGAT1-1
HuGOGAT1-2
HuGOGAT1-3
HuGAD1
HuGAD2
HuGAD3
HuGAD4
HuGAD5
HuGS1
HuGS2
HuGS3
HuGS4
HuGS5
HuGS6
6
Alanine, aspartate and
glutamate metabolism
–log10(P)
5
4
3
2
1
0
0.0
0.2
0.4
0.6
0.8
1.0
Pathway impact
C
5.0
0.0
–5.0
Peel
Pulp
CK30/CK25
CK35/CK25
B25/CK25
B30/CK25
B35/CK25
Blue light
Peel
L-Alanine P
HuAGTs
P F
-POD
Pulp
Alanine, aspartate and glutamate metabolism
F
HuALTs
P F
Pyruvate
P F
L-Aspartate
P
L-Asparagine P F
F
HuMBD9 P
F
HuL-AO P
F
Oxalacetic acid P
HuASN
P
F
HuSSP
P
F
HuASs
P
F
F
-Total sugar
-SOD
-Hydroxyl radical
scavenging ability
-Pectin
-Hemicellouose
-Vanillic acid
-Pipecolic acid
-(E)-2-octenal
-(9Z,12Z,15Z)Octadecatrienoic acid
-Benzene-1,2,4-triol
-Reducing sugar
TCA CYCLE
-Amino acid
-Palmitoleic acid
2-Oxoglutarate
P
F
HuGOGATs P
L-Glutamate P
-Hippuric acid
F
HuGAO P F
γ-Aminobutyric (GABA) P
-Benzeneacetaldehyde
F
HuGSs P
-3-Methylfuran
L-Glutamine P F
F
-14-Methyloxacyclotetradecan-2-one
-Longifolene
F
Antioxidation
Fruit growing
Nutrition
Fig. 6 Significant KEGG pathway analysis and regulatory schematic of blue light on pitaya peel and pulp. A, KEGG pathway
analysis of pitaya peel and pulp metabolomics. The number of metabolites enriched in this pathway is indicated by the size of the bubbles
in the graph. Bubble color represents significance: the redder the bubble, the more statistically significant the difference. CK25, CK30, and
CK35, samples from the control group collected at 25, 30, and 35 days after anthesis, respectively. B25, B30, and B35, samples from the
blue light treatment group at the corresponding time points. B, gene changing patterns in alanine, aspartate and glutamate metabolism
which changed significantly after blue light treatment. Data are presented as the mean±SE (n=3). C, metabolic regulatory schematics
of peel and pulp of pitaya treated with blue light. P and F represent the change patterns in the peel and pulp, respectively, while red and
green indicate increase and decrease, respectively, and black denotes no significant change.
Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
pathway diagram (Fig. 6-C) was drawn. After blue light
treatment, the contents of L-alanine, pyruvate, L-aspartate,
oxalacetic acid, 2-oxoglutarate, L-glutamate, and gammaaminobutyric acid (GABA) were significantly increased, while
L-glutamine and L-asparagine were not detected in the peel
(Fig. 6-C). In the pulp, the contents of pyruvate, L-alanine,
GABA and L-glutamate were significantly decreased, while
L-glutamine and L-asparagine were significantly increased
(Fig. 6-C). Thus, the blue light treatment significantly
influenced the distribution of amino acids, such as L-alanine,
L-aspartate, and L-glutamate in the peel and pulp, affecting
fruit quality. Blue light treatment also increased the contents
of pyruvate, oxalacetic acid and 2-oxoglutarate, which play
roles in the TCA cycle (Fig. 6-C), and directly increased basic
metabolism levels in the peel and pulp of pitaya fruit.
4. Discussion
4.1. Effects of blue light treatment on pitaya fruit yield
Many studies have demonstrated that fruit quality can be
affected by environmental factors, such as light. Light plays
a vital role in flowering, fruit development and ripening (He
et al. 2022). Supplemental LED lighting has been shown to
increase the size of tomatoes, and tomato fruit development
was faster during the night for the plants receiving LED light
(Paponov et al. 2020). In this study, the average fruit weight
was increased by supplemental blue light. Although the control
group had greater average fruit weight than the blue light
treatment group at 25 DAA (Fig. 1-A), the average fruit weight
in the blue light treatment group increased by 79.26% from 25
to 35 DAA, while the growth rate of the control group for the
same time period only increased by 40.75%. This indicates
that the main stage at which blue light significantly promotes
an increase in individual fruit weight is from 25 to 35 DAA.
We further dissected the fruit weight increment by analysing
the relative changes in the peel and pulp weight. During the
key fruit development period from 25 to 35 DAA, the peel
weight decreased by 49.46 and 36.97% in the control and
blue light treatments, respectively (Appendix B), while the pulp
weight increased by 269.23 and 366.08%, respectively. This
indicates that at this stage the peel was beginning to be used
as a resource to provide nutrients for pulp development. At
the same time, the amount of increase in the pulp was much
greater than the amount of decrease in the peel. Therefore,
it can be concluded that the increase in pulp weight in the
later stages of fruit development is the main contributor to the
increase in individual fruit weight under blue light.
We found that blue light treatment increased the contents
of total sugar and reducing sugar in the pulp (Fig. 3-A and
B). Supplemental blue light treatment improved tomato
fruit ripening and quality (He et al. 2022). Amino acids are
essential food compounds and provide important nutritional
value. We found that the content of total amino acids in
the pulp (Fig. 3-C) decreased slowly, while the blue light
treatment retarded the rate of decrease. Therefore, blue
light treatment can improve fruit quality and nutritional
value of pitaya fruit. It is reported that supplemental light
treatment increases biomass accumulation for different plants
(Muhammad et al. 2018; Wu B S et al. 2023). During the fruit
1497
growing period, the contents of total protein (Fig. 3-D) in the
blue light treated group were higher than those in the control
group. It can be inferred that blue light treatment promoted
the accumulation of sugars, amino acids and proteins in the
pulp to a certain extent and improved fruit quality.
It is worth noting that the late stage of fruit development,
i.e., 25 to 35 DAA in pitaya, is particularly important for
fruit weight increase. Therefore, when blue light or other
technological measures are utilized to promote yield in
pitaya, more attention should be paid to the late stage of fruit
development. According to the research of Xiao et al. (2022),
light quality affects plant growth and the functional component
accumulation in fruit, and this study showed consistent
experimental results.
Blue light treatment significantly increased individual fruit
weight, fruit firmness, total sugar content and total amino acid
content of the fruit pulp. It also suppressed the degradation
of hemicellulose and increased pectin content in the peel.
These improvements in nutritional parameters significantly
enhanced both fruit quality and yield. In other fruits, it has
also been reported that blue light treatment increased the
accumulation of sucrose in mango pulp (Ni et al. 2022), and
LED light played an important role in improving grape fruit
quality (Zhang et al. 2021). Our results are consistent with
those of Liu et al. (2025) that cell wall materials, cellulose,
and hemicellulose show a declining trend during apple
development, positively correlating with the reduction in fruit
firmness.
4.2. Effects of blue light treatment on pitaya fruit antioxidative activities
CAT, POD and SOD are enzymes related to antioxidant
activities (Ling and Zhang 2013; Zhang et al. 2024). The blue
light treatment increased CAT (Fig. 2-E) and POD (Fig. 2-G)
activity. Although SOD activity gradually decreased during fruit
growth, the blue light treatment significantly enhanced SOD
activity (Fig. 2-I) compared with the control group. Compared
with the control group, the hydroxyl radical scavenging ability
(Fig. 2-H) was increased after blue light treatment, with
significant changes from 25 to 35 DAA. Flavonoids play
an essential role in regulating oxidative stress and are an
important source of daily intake of antioxidant supplements
(Wang et al. 2022). Compared with the control group, the
blue light treatment significantly increased the flavonoid
content in the fruit peel, which could be a result of significant
changes in free radical scavenging ability. In an earlier study,
supplemental blue light treatment on tomato fruit significantly
enhanced the contents of total flavonoids, vitamin C, as well as
antioxidant activity (Aalifar et al. 2020; He et al. 2022; Zhang
et al. 2022). Therefore, it can be hypothesized that blue light
treatment improved the antioxidant capacity of the fruit, which
may be mainly related to the changes in the activity of SOD,
POD, and CAT, as well as the increase in flavonoid content,
resulting in enhanced scavenging capacity of hydroxyl radicals.
4.3. Dynamic accumulated metabolites in pitaya fruit
in response to blue light treatment
Light is one of the most important environmental factors that
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Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
affects plant growth and development. It also influences
plant morphogenesis, photosynthesis, metabolism and
signal transduction (Yang et al. 2020). A total of 39 volatile
compounds in red pitaya changed significantly after blue
light treatment during storage (Wu et al. 2019). In a previous
study, it was reported that middle-intensity blue light treatment
was the most effective condition for developing an intense
and persistent fruity and floral scent (He et al. 2025). In our
study, blue light treatment accelerated the accumulation
of key metabolites in peel and pulp, and there were some
differences in the effects of blue light treatment between the
peel and the pulp.
With blue light treatment in pitaya peel, the content
of several metabolites in the peel (Fig. 5-C) increased
significantly, except for (E)-2-hexen-1-ol. (E)-2-Octenal was
found to be a special differentially accumulated aldehyde
in this study. During pitaya development, its levels tended
to decrease in both control and blue light treatment groups,
but supplemental blue light significantly increased the
accumulation of (E)-2-octenal at various stages of peel
development from 25 to 35 DAA. It is reported that (E)2-octenal was identified as the most efficient airborne
signal in Nicotiana benthamiana plants induced by tobacco
mosaic virus (TMV), which can prime the jasmonic acid
(JA)/ET pathway and then activates immune responses,
ultimately leading to enhanced TMV resistance in adjacent
N. benthamiana plants (Hong et al. 2023). Thus, blue light
treatment significantly affected the accumulation pattern of
(E)-2-octenal, and has the potential to improve fruit resistance
to biotic stress by promoting the accumulation of (E)-2-octenal
volatiles. Furthermore, five important volatile compounds,
including three acids: (9Z,12Z,15Z)-octadecatrienoic acid,
vanillic acid, and pipecolic acid; one aldehyde: (E)-2-octenal,
and one other compound: benzene-1,2,4-triol were enhanced
after blue light treatment. With a vanilla-like smell and
taste, vanillic acid has always been in high demand in the
pharmaceutical, cosmetic, food, flavor, alcohol and polymer
industries. It could also regulate cardiovascular diseases and
may have therapeutic utility clinically (Lashgari et al. 2023).
Pipecolic acid is a putative mediator of encephalopathy of
cerebral malaria, with neuromodulation roles (Keswani et al.
2022). These findings suggest that blue light treatment
significantly promoted the accumulation of bioactive
compounds in the peel. Additionally, it was reported that (E)2-hexen-1-ol was closely correlated with Rubus coreanus
(RC) fruit ripening, with its content increasing during RC
fruit ripening (Yu et al. 2019). Compared with the control
group, (E)-2-hexen-1-ol decreased markedly after blue light
treatment. (E)-2-Hexen-1-ol is an alcohol compound with a
grass-like aroma, and the decrease in its content caused by
blue light treatment helps to diminish grassy notes to enhance
the overall sensory profile of the pitaya fruit. In addition to
enhancing the accumulation of volatile compounds in the
peel of pitaya fruit, blue light treatment can also increase the
release of bioactive compounds to a certain extent.
Previous studies have irradiated grape leaves with
blue light, and it was found that blue light improved fruit
composition (Li C X et al. 2017). Six acids (Fig. 5-D)
gradually accumulated with fruit development in the pitaya
pulp: palmitoleic acid, cis-7-hexadecenoic acid, n-decanoic
acid, octanoic acid, pentanoic acid, and hippuric acid. Among
them, the level of hippuric acid was significantly increased
by blue light treatment, and its derivatives showed good
antiretroviral potential, maximum fungicidal and cytotoxic
activities (Tehreem et al. 2019). In addition, as organic acids
are used as antimicrobial agents in the food industry (Coban
2020), it could be hypothesized that blue light treatment
could potentially endow pitaya fruits with better antibacterial
properties, which can help reduce the probability of fruit
decay during storage, and thus potentially extend the shelf
life of pitaya fruits.
Compared with the control, the levels of 3-methyl-3-buten1-ol and 2-ethyl-1-hexanol were slightly decreased by the blue
light in the pulp. Related studies have shown that aldehydes
have antibacterial activity and are effective agents in regulating
microbial growth (Darwin and Stanley 2022). The contents
of differential aldehydes (Fig. 5-D) increased significantly
after blue light treatment, and the change was most obvious
for benzeneacetaldehyde. Benzeneacetaldehyde, detected
in the flowers of Rhododendron species (Qian et al. 2019)
and in the leaves of Cantium parviflorum Lam. (Kala and
Ammani 2017), has been reported to possess antioxidant
(Tanapichatsakul et al. 2017) and antimicrobial (Kala and
Ammani 2017) properties, and has a fruity, floral, and sweet
odour. The same patterns were observed for 2-methylbutanal
and 3-methylbutanal. Therefore, we hypothesize that blue
light treatment can increase the biotic resistance of pitaya
fruit by increasing the content of aldehyde compounds
especially benzeneacetaldehyde in the pulp. Moreover,
aldehydes are important aroma components of pitaya fruits
(Wu et al. 2020a; Wu Q et al. 2023), so the enhancement
of these compounds suggests that blue light treatment
increased the representative flavor of pitaya. To a certain
extent, blue light treatment enhances the accumulation of
characteristic components in pitaya and helps promote the
growth and development of the fruit. Overall, the blue light
treatment induced a positive response and increased the
accumulation of aldehydes and acids in the pulp of pitaya,
which could potentially enhance the biotic resistance and
flavor characteristics of the fruit.
5. Conclusion
In pitaya, supplemental blue light significantly increased
fruit weight by promoting pulp biomass accumulation,
improved fruit firmness by increasing pectin content, retarded
hemicellulose degradation, and enhanced the activity of
POD and SOD as well as the content of flavonoids, thereby
improving the antioxidant capacity of the fruit. Specifically,
blue light treatment significantly altered alanine, aspartate,
and glutamate metabolism, promoted the accumulation of
bioactive ingredients in the peel, and significantly altered the
accumulation of volatile compounds - especially increasing
organic acids, esters and terpenes in the pulp - thereby
affecting fruit flavor.
Acknowledgements
This work was supported by the National Key Research and
Qingming Sun et al. Journal of Integrative Agriculture 2026, 25(4): 1488–1500
Development Project, China (2022YFB3604604), the Rural
Revitalization Project from Guangdong Province, China
(2022-NPY-00-034). The authors would like to thank Ms.
Connie Alson (NY, USA) for help with language review.
Declaration of competing interest
The authors declare that they have no conflict of interest.
Declaration of generative Al and Al-assisted
technologies in the writing process
The authors declare that they did not use AI in the preparation
and writing of this manuscript.
Appendices associated with this paper are available at
https://doi.org/10.1016/j.jia.2025.11.034
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Executive Editor-in-Chief Sanwen Huang
Managing Editor Lingyun Weng