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African Journal of Biotechnology Vol. 10(8), pp. 1347-1352, 21 February, 2011
Available online at http://www.academicjournals.org/AJB
DOI: 10.5897/AJB10.882
ISSN 1684–5315 © 2011 Academic Journals
Full Length Research Paper
Difference in photosynthetic performance among three
peach cultivars grown under low light conditions in
greenhouses
Shaohui Wang, Yun Kong and Yuncong Yao*
New Technological Laboratory in Agriculture Application in Beijing ,Plant Science and Technology College, Beijing
University of Agriculture, Beijing, 102206.
Accepted 11 November, 2010
The effects of low photosynthetic photon flux density (PPFD) on greenhouse grown peach trees
(‘Qingfeng’: Prunus persica L. Batsch, ‘NJN76’: Prunus persica L. Batsch and ‘Maixiang’: P. persica var.
nectarine) were investigated. Difference in photosynthesis rate (Pn) and stoma morphology among
cultivars were studied. Furthermore, chlorophyll content, leaf thickness and photosynthesis enzyme
activity were analyzed. Results showed that when PPFD was reduced to 80% of control, Pn decreased in
all three cultivars. The reduced net photosynthesis rate was associated with decreased stoma density,
stoma aperture and stoma conductance (Cs), as well as chlorophyll a (Chla) and b (Chlb) content in all
cultivars; leaf mass per unit area (LMA) and thickness of upper and lower layers of leaf epidermis also
declined. At 80% PPFD, the variation pattern of ribulose bisphosphate carboxylase (RuBPCase), Ca2+-
adenosinetriphosphatase (Ca2+-ATPase) and Mg2+- adenosine triphosphatase (Mg2+-ATPase) activities,
together with nicotinamide adenine dinucleotide phosphate (NADPH) content and photosynthetic O2
evolution rate among the three cultivars was the same as the pattern of LMA. Time course analysis
showed that the net photosynthesis rate of ‘Maixiang’ was higher than that of the other two cultivars
from 10:00 to 14:00. Though the parameters mentioned above decreased under shade in all the three
cultivars, ‘Maixiang’ still had higher Pn than that of the other two cultivars. Our results indicated that
‘Maixiang’ is probably more suitable to grow in low PPFD than ‘Qingfeng’ and ‘NJN76’, especially in the
early spring season in order to get higher market value.
Key words: Prunus persica L., low light, photosynthesis, RuBPcase, Ca2+-ATPase, Mg2+-ATPase, NADPH
content.
INTRODUCTION
In China, increasing number of fruit growers are growing
peach trees in greenhouses, rather than the open field,
for early fruit harvest and better marketing. Commonly,
greenhouse grown peach trees are grown in conditions
*Corresponding author. E-mail: yaoyc_20@ 126.com. Fax: 86
10 80799000.
Abbreviations: PPFD, Photosynthetic photon flux density;
RuBPCase, bisphosphate carboxylase; LMA, leaf mass per
unit area; Ca2+-ATPase, Ca2+-adenosinetriphosphatase; Mg2+-
ATPase, Mg2+-adenosine triphosphatase; NADPH,
nicotinamide adenine dinucleotide phosphate.
where natural sunlight is the sole source of illumination
and there is no additional heating system. In such
greenhouses in Beijing 39.92°N, China, peach trees
blossom in February and fruit can be harvested in April.
During that period, from February to April, the photo-
synthetic photon flux density (PPFD) is about 200 ~ 300
mol m–2 s–1, and peach trees’ canopies expand and fill
up space quickly (Yao et al., 2007). However, many
upright and vigorous shoots are produced on the trees,
resulting in shading, especially of the low layers of peach
tree canopies; and when combined with the poor light
condition inside the greenhouse, the productivity of the
peach trees is markedly reduced.
It is well known that plant growth and development is
significantly affected by environmental factors. If plants
1348 Afr. J. Biotechnol.
Figure 1. Leaves selected for measurement in this paper
grow continuously under low or high light condition,
changes at biochemical, ultrastructural, anatomical or
even morphological levels occur (Adamson et al., 1991).
Plant adaptation to weak light is closely related to many
internal and external factors. Plant light-saturated photo-
synthetic capacity, dark-adapted quantum efficiency of
photosystem II and relative chlorophyll content are
employed to characterize plant responses to different light
conditions (Griffin et al., 2004). Plant shade tolerance is
characterized by morphological and physiological traits
that enhance the net rate of carbon capture in low light.
For example, in shaded ginger plants (0 to 80% of full
sunlight exposure), chloroplast size and leaf number
decreased, while the leaf area, leaf thickness, the
numbers of grana lamella, special grana lamella and starch
grains increased (Zhang et al., 1999). The mesophyll
thickness of poinsettia decreased significantly when
shade increased from 30 to 92% (Galicia-Jimenez et al.,
2001). Additionally, when plants grow under low light, the
number of palisade cells, chlorophyll content, the ratio of
chlorophyll a/b and the electron transfer rate declined. In
cotton, low light radiation causes a significant decrease in
both ribulose bisphosphate (RuBP) carboxylation efficiency
and maximum regeneration rate (Yang et al., 2005). It
was also reported that carbon allocation to roots is
restricted under low light conditions (Paez et al., 2000).
Griffin et al. (2004) suggested that photosynthesis rate,
carbohydrate ability, chlorophyll content and the
characteristics of chloroplast might be used as indices to
assess the ability of plants under low PPFD.
Peach trees grow in greenhouses where solar radiation
is weak because of shading film and overlapped cano-
pies. In this study, we aimed to investigate the effects of
low PPFD on leaf morphology, stoma density and
chlorophyll content in leaf, leaf photosynthesis rate, and
ribulose bisphosphate carboxylase (RuBPCase) activity
in three different peach cultivars: Prunus persica L. Batsch
‘Qingfeng’ and Maixiang’, as well as P. persica var.
nectarine ‘NJN76’, all of which are commonly planted in
greenhouses.
MATERIALS AND METHODS
Plant materials and treatments
Three-year-old trees of P. persica L. Batsch ‘Qingfeng’, ‘Maixiang’
and P. persica var. nectarine ‘NJN76’ were used in the present
investigation at Beijing University of Agricultural, Beijing, China.
Peach seedlings each with ten leaves were transplanted into 30 ×
40 cm clay pots containing 5.5 kg of fertile alluvial soil, one plant
per pot. All pots were placed in a greenhouse (60 × 6 m). One year
later, January 1, 2006, the following treatments were implemented:
1) non-shading, full sunlight exposure (CK), and 2) 80% of full
sunlight exposure (T1). All peach trees were covered with the same
double layer shading film from the top, so that the expected FFFD
in T1 were maintained at canopies. LI-1400 data logger and
quantum sensor Li-190SA were used to observe the PPFD for each
treat-ment. Triple replications were arranged in randomized blocks
and there were 10 potted trees for each of two different shading
treatments. All the peach trees were irrigated with Murashige and
Skoog (MS) solution. The fully expanded, upper canopy leaves
were selected for anatomical study, photosynthetic study and other
studies as indicated Figure 1 (Kong et al., 2007).
Net photosynthesis rate
Net photosynthesis rate (Pn) was measured one month after
shading treatment started using a portable photosynthesis system
(LI-6400, Li-Cor, Lincoln, NE, USA). It was measured at 400 ±
10 mol mol–1 CO2 concentrations in the inflowing air, ambient rela-
tive humidity 60 ± 5 % and leaf temperature of 25°C. Data were
collected from 6:00 to 18:00 h. The leaves for net photosynthesis
rate measurement were as shown in Figure 1.
Chlorophyll content
Six mature leaves as showed in Figure 1 were selected for
chlorophyll content determination immediately after photosynthetic
rate was measured; the leaves were sampled, homogenized with
15 ml of 95% ethanol and centrifuged at 3000 ×g for 5 min. The
upper solution was measured with a UV-2001 spectrophotometer at
645 and 663 nm. Chlorophyll content was calculated as described
by Arnon (1949).
Wang et al. 1349
Table 1. Changes in chlorophyll a (Chla), chlorophyll b (Chlb) contents [mg g-1(FM)], stoma density (number mm–2),
stoma aperture (µm) and stoma conductance (µmol m-2s-1) in leaves of peach plants grown under non-shading, full
sunlight exposure (CK) and 80% of full sunlight exposure (T1).
Cultivar Treatment Chlb (mg /gFM) Chla (mg/gFM) Stoma density
(/mm2)
Stoma conductance
(µ
µµ
µmol/ m2s1 )
Qingfeng CK 0.20b 0.28a 324a 0.33a
T1 0.23a 0.32a 298b 0.24b
Maixiang CK 0.24b 0.31b 277a 0.35a
T1 0.39a 0.42a 260b 0.27b
NJN76 CK 0.23b 0.30a 301a 0.33a
T1 0.26a 0.36a 276b 0.24b
For each treatment, statistical differences among irradiance treatments were analyzed by LSD test. Values followed by different
letters are significantly different (p < 0.05).
Stoma density and aperture
Mature leaves as defined in Figure 1 were selected for the present
investigation of stoma density and aperture according to Olmez et
al. (2006).
Leaf area and leaf mass per unit area
Leaf area was measured using CID CAF1-CI-203 leaf area instru-
ment. For dry mass (DM) determination, samples were first kept at
110°C for 15 min and then maintained at 80°C until constant mass.
Leaf mass per unit area (LMA) was calculated as leaf dry mass/leaf
area.
Ultrastructure of chloroplast
For chloroplast ultrastructure investigation, the mature leaves were
cut into small pieces (0.5 x 0.5 mm) and immediately fixed in 5%
glutaraldehyde (in sodium-cacodylate buffer, pH 7.2) for 3 h as
described by Pilarski (1993). The specimens were sectioned and
stained with uranium acetate-lead citrate, observed and photo-
graphed under a JEM-100 CX transmission electron microscope.
Photosynthetic O2 evolution rate
Photosynthetic O2 evolution rate was measured with a Clark-type
oxygen electrode (Hansatech, King’s Lynn, UK) under white light
with a saturating PPFD (800 µmol m-2 s-1) as described by van
Gorkom and Gast (1996).
ATPase and RuBPCase activities
The activities of Ca2+-ATPase and Mg2+-ATPase were analyzed
according to Liu and Hao (1990) and Cai et al. (1980). Ribulose
bisphosphate carboxylase (RuBPcase) activity and nicotinamide
adenine dinucleotide phosphate hydrogen (NADPH) content were
determined according to Khanna-Chopra (1982) and Ye and Zhao
(1990), respectively.
Statistics
Results represented the average of independent experiments in
three replicates. Data were analyzed using the statistical analysis
systems (SAS). Each plant from an individual treatment was taken
as a replicate. The means of each parameter were compared
among treatments using a one way analysis of variance (ANOVA) in
the General Linear Model Procedure of SPSS (version 12, SPSS,
Chicago, IL, USA). Least significant differences (LSD) were
considered between individual treatments when the F-test of the
ANOVA was significant at p < 0.05.
RESULTS
Chlorophyll content
Peach leaf chlorophyll contents significantly increased
under 80% PPFD when compared with their corresponding
controls in the unshaded treatment (Table 1): leaf Chla
content of ‘Maixiang’ increased by 20.8%, ‘Qingfeng’ and
‘NJN76’ increased by 15.0 and 13.0% respectively.
Nevertheless, whether shaded or not, leaf Chla content of
‘Maixing’ was the highest among all the three cultivars.
The variation pattern of Chlb was the same as Chla under
80% PPFD among all cultivars.
Stoma
Stoma density in ‘Maixiang’ at 80% PPFD decreased
moderately (277 to 260 number mm-2) when compared
with the decreases in ‘Qingfeng’ (from 324 to 250 number
mm-2) and ‘NJN76’ (301 to 243 number mm-2). The res-
ponse of stoma apertures and stoma conductance due to
shade were similar to those in stoma density. Shading
had less effect on ‘Maixiang’ stoma density, stoma aper-
ture and stoma conductance than that of ‘Qingfeng’ and
‘NJN76’.
Leaf morphological characteristics
Compared with the non-shade control, leaf areas and
LMA values of all the three cultivars at 80% PPFD
decreased with little significant difference (Table 2).
Shading at 80% PPFD, decreased LMA values in
‘Qingfeng’ and ‘NJN76’ was more than that of ‘Maixiang’,
‘Maixiang’ still has the highest LMA values among all the
1350 Afr. J. Biotechnol.
Table 2. Changes in leaf areas (cm2), leaf mass per unit area (LMA) (mg cm-2), upper epidemic thickness (UET) (µm), lower
epidemic thickness (LET) (µm), palisade tissue thickness (PTT) (µm) and sponge tissue thickness (STT) (µm)] in leaves of peach
plants grown under non-shading, full sunlight exposure (CK) and 80% of full sunlight exposure (T1).
Cultivar Treatment Leaf area (cm
2
) LMA (mg/cm
2
) UET (µm) LET (µm) PTT (µm) STT (µm)
Qingfeng CK 34 6.35 13.2 13.0 50.5 62.3
T1 31.3 HS 4.3 HS 10.2 HS 10.3 S 55.5 HS 60.3 NS
Maixiang CK 33.6 6.4 13.1 13.0 54.6 64.0
T1 30.8 HS 5.2 HS 10.2HS 9.2 HS 57.6 NS 59.8 NS
NJN76 CK 34.4 6.5 14.3 12.7 55.4 66.9
T1 29.7 HS 3.90 HS 10.8 HS 9.4 HS 59.8 NS 61.3 NS
For each treatment, statistical differences among treatments were analyzed by T test. Values followed by different letters indicated
significance of P 0.01 (HS), P 0.05 (S) and P (NS), respectively.
Figure 2. Effect of shading on net photosynthesis rates of three peach cultivars grown under greenhouse of non-
shading, full sunlight exposure (CK, control, filled triangle) and 80% of full sunlight exposure (T1, open rhombus). The
data represent the means ± SE of nine replicates.
cultivars. Thickness of leaf upper or lower epidermis also
decreased slightly among all the three cultivars, no
obvious difference was observed among them. At 80%
PPFD, the thickness of palisade tissue increased, the
thickness of sponge tissue reduced, but there was no
significant difference among all the cultivars.
Net photosynthesis rate
It is interesting to note that although Pn of shade plants
was lower than their corresponding control plants (Figure
2), at 80% PPFD, ‘Maixiang’ still exhibited a slightly higher
photosynthesis rate between 10:00 and 14:00 than the
other two cultivars, suggesting that ‘Maixiang’ was more
tolerant to low PPFD.
RuBPcase activity
Leaf ribulose bisphosphate carboxylase (RuBPcase)
activities of ‘Maixiang’ and ‘Qingfeng’ were higher than
that of ‘NJN76’ when not shaded (Table 3); while under
80% PPFD, leaf RuBPcase activity in ‘Maixiang’, ‘Qingfeng’
and ‘NJN76’ all declined. However, the RuBPcase activity
in ‘Maixiang’ was slightly higher than that of ‘Qingfeng’ and
‘NJN76’.
Ca2+-ATPase and Mg2+-ATPase activity
Shade decreased the activities of Ca2+-ATPase and Mg2+-
ATPase in the three cultivars (Table 3), whereas Ca2+-
ATPase activity of ‘Maixiang’ was still significantly higher
than that of ‘NJN76’ and ‘Qingfeng’ at 80% PPFD. This
suggest that ‘Maixiang’ was more suitable to low light
conditions than both ‘Qingfeng’ and ‘NJN76’.
NADPH content
The pattern of response in NADPH content among the
Wang et al. 1351
Table 3. Changes of ribulose bisphosphate carboxylase activities (RuBPcase) [µmolCO2.min-1g-1FW], Ca2+- and Mg2+ adenosinetriphosphatase activities (Ca2+- and Mg2+-ATPase)
[µmPi·mg-1chl], nicotinamide adenine dinucleotide phosphate contents (NADPH) [nmol.mg-1] and photosynthetic O2 evolution rates [µmol.O2g-1FWhr-1] in leaves of peach plants grown
under non-shading, full sunlight exposure (CK) and 80% of full sunlight exposure (T1).
Cultivar Treatment RuBPcase activity
(µmolCO2.min-1g-1FW)
Ca
2+
-ATPase activity
(µ
µµ
µmPi·mg-1
chl
)
Mg2+-ATPase activity
(µ
µµ
µmPi·mg-1chl)
NADPH content
(nmol.mg-1chl)
Photosynthetic O2 evolution rate
(µmol.O2g-1FWhr-1)
Qingfeng CK 6.01a 756.3a 702.2a 5.08a 163.2±7.3
T1 5.01b 665.7b 609.2b 4.18b 95.1±5.0
Maixiang CK 6.00a 735.7a 678.9a 4.62a 138.0±7.1
T1 5.34a 702.8b 643.7b 3.91b 129.0±4.3
NJN76 CK 5.47a 742.1a 693.3a 4.40a 91.8±6.1
T1 4.12b 604.5b 501.8b 3.580b 74.1±6.8
For each treatment, statistical differences among treatments were analyzed by LSD test. Values followed by same letters in the same column are of not significantly different (p < 0.05).
cultivars was the same as that of Ca2+-ATPase
and Mg2+-ATPase activity, suggested that
‘Maixiang’ was more adapted to lower light
conditions (Table 3).
Photosynthetic O2 evolution rate
Photosynthetic O2 evolution rate of ‘NJN76’ was
the lowest among the three cultivars under non-
shade, followed by ‘Maixiang’ and ‘Qingfeng’
(Table 3). Eighty percent PPFD markedly decreased
the photosynthetic O2 evolution rates of the three
cultivars, but ‘Maixiang’ still remained the highest
photosynthetic O2 evolution rate among all the
three cultivars.
DISCUSSION
Low PPFD, photosynthesis rate and plant
growth
In response to reduced PPFD, peach leaf area
increased, shade-grown leaves were thinner, flatter
and darker green than sun-grown ones (Nii and
Kuroiwa, 1988). In the present study, we observed
that the leaf areas of all cultivars decreased due
to shading treatments, which contrasts with the
findings of Nii and Kuroiwa (1988), who reported
that the shade increased peach leaf area.
Perhaps different treatments and different PPFD
resulted in different conclusion. However, other
workers have reported that at low PPFD, there is
a characteristic increase in grana stacking, with
no change in chlorophyll a/b ratio in ornamental
aroids and increased chlorophyll content per unit
leaf area and per dry weight (Zhang et al., 1999).
But in the present investigation, we observed an
increase in chlorophyll content as the intensity of
shading increases. This is supported by the
observations of Galicia et al. (2001) who found
that chlorophyll content of poinsettia increa-ses
steadily with shading. In this study, light affected
peach leaf stoma aperture size and stoma
conductance, and stoma density decreases with
shading (Lenny et al., 2004).
The reduced chlorophyll content and stoma
conductance contributed to the decreased
photosynthesis rate at 80% PPFD. It is interesting
to note that at 80% PPFD stoma density, conduc-
tance and aperture size in ‘Maixiang’ declined less
than that of ‘Qingfeng’ and ‘NJN76’, and the ability
to maintain higher photosynthesis rate at 80%
PPFD suggested that ‘Maixiang’ might be more
tolerant to low light condition than the other two
peach cultivars.
Low PPFD, ATPase and RuBPcase activity
Adenosine triphosphate (ATP) is an important
cofactor of RuBPcase in isolated chloroplasts.
ATPase activity and the extent of oligomerization
of RuBPcase are closely linked. RuBPcase oligo-
merization is highly specific for Mg2+-ATP, and
exhibits a response to ATP concentration, being
inhibited by ADP (Liu et al., 2006). The concen-
tration of Mg2+ in the chloroplast stroma is light-
dependent and is of regulatory significance for
other reactions of the Benson-Calvin cycle. Illumi-
nation generates an increase in the concentration
of stroma Mg2+ (Sumio et al., 2004) and the stromal
ATP/ADP quotient (Sumio et al., 2004). In the
present study, the RuBPcase activity was coupled
with Ca2+- and Mg2+- ATPase activities. Shading at
80% PPFD led to a decrease in the activities of
RuBPcase, Ca2+- and Mg2+- ATPase, but much
1352 Afr. J. Biotechnol.
less in ‘Maixiang’ than in the other two cultivars,
suggesting again, that ‘Maixiang’ would be more suitable
for indoor greenhouse conditions.
The activity of RuBPcase, carbohydrate rate and electron
transport rate has previously been reported (Zhou et al.,
2007). At low PPFD, the reduced photosynthetic O2
evolution rate was probably due to the suppression of
RuBPcase activity, leading to decreased carbon fixation.
In the present investigation, though RuBPcase activity of
all the three cultivars decreased due to shading treat-
ment, RuBPcase activity in ‘Maixiang’ was still the highest
among all the tested cultivars.
Low PPFD and NADPH
There was a strong correlation between PPFD, electron
transport rate and NADP-MDH activation. Decreased
NADPH/NADP+ ratio has two main implications for carbon
fixation. Firstly, the lack of reducing equivalents limits the
ribulose bisphosphate (RuBP) regeneration. Secondly,
the consumption of adenosine triphosphate (ATP) may be
severely restricted, thus compensating for the decreased
rate of ATP synthesis. As reported previously (Zhou et al.,
2007), the decreased CO2 assimilation rate in plants is
associated with reduced RuBP concentration. The reason
for the decreased RuBP concentration is straight forward:
the reduced amount of NAPDH forms a bottleneck in the
regeneration pathway and occurs with low light. In our
study, we noticed that under low light, the NADPH con-
tents in all the three peach declined. It was assumed that
low light induced the decrease of electron transport rate
in the plants, subsequently leading to the decreased
synthesis of ATP and NADPH and further impairing RuBP
regeneration capacity. Among the three cultivars tested,
all the indices tested in ‘Maixiang’ decreased less than
the other two cultivars, indicating that ‘Maixiang’ was more
suitable for greenhouse conditions than the other two
cultivars.
In summary, our present study strongly suggests that
compared with ‘Qingfeng’ and ‘NJN76’, ‘Maixiang’ was
more adaptive to lower light, with a slightly reduced Chla
content, stoma density, stoma aperture size, stoma con-
ductance, LMA and chloroplast number, all contributed to
the less decreased photosynthesis rate when shaded at
80% PPFD. Hence, ‘Maixiang’ is the best cultivar to be
planted in greenhouse when the sunlight is low.
ACKNOWLEDGEMENTS
This work was supported by Beijing Natural Science
Foundation of China (6992008) and Beijing Municipal
Education Commission Science and Technology Develop
Programs of China (KM200310020080). The anonymous
reviewing editor and reviewers are gratefully thanked for
their constructive comments.
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