全 文 ：Effect of Radiative Forcing on Growth and
Photosynthetic Responses of Elaeocarpus
glabripetalus Merr.
Shuang YANG, Hong JIANG*, Xiuli ZHAI
Zhejiang Provincial Key Laboratory of Carbon Cycling in Forest Ecosystems and Carbon Sequestration, Zhejiang Agriculture and
Forestry University, Hangzhou 311300, China
Supported by the Major International Cooperation Project of the Ministry of Science and
Technology of China (20073819); the National High-tech R&D Program of China
(2009AA122001, 2009AA122005); the Major Basic Project of the Ministry of Science
and Technology of China (2007FY110300-08); the State Key Development Program for
Basic Research of China (2010CB950702, 2010CB428503); the National Natural
Science Foundation of China (40671132); the Major Project for Science and Technology
of Zhejiang Province, China (2008C13G2100010).
*Corresponding author. E-mail: jianghong_china@hotmail.com
Received: February 28, 2012 Accepted: April 16, 2012A
Agricultural Science & Technology, 2012, 13(6): 1240-1246
Copyright訫 2012, Information Institute of HAAS. All rights reserved Agronomy and Forestry
Abstract [Objective] This study aimed to reveal the impact of radiative forcing on
the woody plants in subtropical regions of China through the study on the effect of
radiative forcing on growth and photosynthetic responses of Elaecarpus glabripetalus
Merr. seedlings. [Method] Three gradients of radiative forcing treatments were applied
to the species namely, control group (100% natural light), weak radiative forcing
group (39% natural light) and strong radiative forcing group (16% natural light). The
relative contents of chlorophyll, photosynthetic parameters of E. glabripetalus in dif-
ferent periods were measured to analyze the effects of different gradients of radiative
forcing on plant height, ground diameter, chlorophyll content, gas exchange parame-
ters, light response cure parameters. [Result] The increased ground diameter of
E. glabripetalus in different treatments was the control > weak radiative forcing
group > strong radiative forcing group; the increased plant height in the early period
was strong radiative forcing group > weak radiative forcing group > control, but there
was no significant difference during the late period; the relative content of chlorophyll
was strong radiative forcing group > weak radiative forcing group > control. The light
compensation point (LCP), light saturation point (LSP) and the maximum net photo-
synthetic rate (Amax) were reduced in radiative forcing treatments. The stomatal con-
ductance (Gs), transpiration rate (Tr) of E. glabripetalus in strong radiative forcing
group were significantly smaller than that in the control group, while there was no
significant change in dark respiration rate (Rd) and apparent quantum yield (AQY).
[Conclusion] In summary, the radiative forcing can change the environmental factors
which have significant effect on the ground diameter, plant height, relative content of
chlorophyll and photosynthetic physiological parameters, but with the processing of
treatment the effects on ground diameter and plant height increase are not significant
in the late period, indicating that E. glabripetalus seedlings have some resistance
and adaptability to the radiative forcing environment.
Key words Radiative forcing; Elaeocarpus glabripetalus Merr.; Chlorophyll relative
content; Photosynthetic characteristic
H uman production and dailyactivities, such as the burningof fossil and non-fossil fuels,
transportation, and a variety of
industrial and production activities,
cause a lot of dust and smoke
emissions to the atmosphere, and the
dust suspended in the atmosphere, on
the one hand, can reflect part of the
solar radiation back into space,
weaken the solar radiation reaching
the earth’s surface, reducing the solar
energy received by the earth’s sur-
face; on the other hand, the hygrosco-
picity dust can promote the surround-
ing water vapor condensation as cond-
ensation nuclei, which can increase
the low clouds, fog, haze, further
reducing the solar energy received by
the ground surface. These sources of
radiative forcing have an effect on the
photosynthetically active radiation and
climatic factors, thereby affecting plant
growth and development [1]. The study
of Gu et al. [2] shows that the diffuse
radiation caused by the radiative
forcing factors can lead to higher light
use efficiencies by plant canopies,
indicating that diffuse radiation can
affect the terrestrial ecosystem pro-
ductivity. Based on the estimates of
aerosol optical depths over China and
the effect of these optical depths on
the solar irradiance reaching the earth
surface, Chameides [3] asses-sed the
effects of radiative forcing on winter
wheat and rice yields in Nanjing. The
results show that the radiation
reduction presents linear relationship
with the yield reduction. Cohan et al. [4]
analyzed the combined effects of
available radiation reduction and di-
ffuse solar radiation increase on
vegetation productivity during summe-
rtime at midlatitudes, found that
different atmospheric aerosol optical
depth and cloud cover at different
regions may either harmful or
beneficial for the growth of vegetation.
As on aspect of the parasol effect of
global change, radiative forcing has
received much attention in recent
years[5-7], and many studies have devo-
ted to the response of plants to
radiative forcing from the changes of
plant biomass, photosynthetic and
physiological aspects[8-10], but most stu-
dies are still concern on changes of
light intensity radiation amount, i.e.,
DOI:10.16175/j.cnki.1009-4229.2012.06.038
Agricultural Science & Technology
Vol.13, No.6, 2012 Agricultural Science & Technology
2012
the effect of shade on plants. To better
understand the mechanism and
process of the effect of radiative
forcing on plant physiology and
biochemistry, we selected Elaeocar-
pus glabripetalus Merr., a genus of
tropical and subtropical evergreen
trees and shrubs, as the materials to
study the effect of radiative forcing on
the E. glasbripetalus seedlings to
comprehensively understand the phy-
siological and ecological response of
E. glasbripetalus seedlings to radiative
forcing, with the aim to provide basis
for the study on the effect of radiative
forcing on plants.
Materials and Methods
General situation of the study area
The study area was the field test
canopy of Zhejiang Agricultural Univer-
sity, located in Lin’an City, Zhejiang
Province (119°42′ E, 30°14′ N). The
area belongs to the mid-latitude no-
rthern tropical monsoon climate with
four distinct seasons, mild climate,
abundant rainfall , annual rainfall of
1 400 mm, average annual tempera-
ture of 15.8℃.
Experimental material processing
Two arc sheds with the size of 15
m × 9 m were built by galvanized small
steel tubes (diameter of 25 mm, wall
thickness of 2 mm) in the open field.
Two black shade nets with different
shading rates were selected to cover
the steel frame. The surrounding
bottom lines of the shading nets were
about 15 cm from the ground to
facilitate ventilation. The photosyn-
thetically activeradiation sensor, which
was connected with the HOBO small
automatic weather station data logger
(Onset Computer Corporation, USA),
was used to measure the photosyn-
thetically active radiation of full natural
light and the two shading nets in May
2008, July 2008 and September 2009,
respectively. The measurements were
conducted every 10 s, and the mean
values were automatically recorded
every 10 min. After measured the
photosynthetically active radiation
under full natural light and the 2
shading nets in May, July and
September, the total photosynthe-
tically active radiation (or average
photosynthetically active radiation) of
the two shading sheds in 1 d was
compared with the total photosynth-
etically active radiation (or average
photosynthetically active radiation)
under full natural light, obtaining that
the photosynthetically active radiation
of the two shading treatments in
different seasons was 38%-40% and
15% -17% of that of the full natural
light. The shading shed with the light
intensity of 38%-40% of natural light
was set as the weak radiation forcing
processing gradient, and the shading
shed with the light intensity of 15% -
17% of natural light was set as the
strong radiation forcing processing
gradient. Another plot with the same
size and water and fertilizer conditions
was selected as the control area to
conduct the radiative forcing exper-
iment. Totally 90 E. glasbripetalus
seedlings with consistent sizes and
growth were selected (average plant
height of 40.29 cm, average diameter
of 0.56 cm) in early 2008 and
transplanted to the experimental
sheds and the control area. There
were a certain distance between
plants to avoid mutual shading, and
the conventional cultivation and
management was adopted. The
measurement began in May 2008.
Research method
Temperature and humidity meas-
urements iButton (information
button) (Dallas, USA) was used to
collect the temperature and humidity of
air and soil under different treatments.
The collection frequency was 1 800s,
and the iButton was placed at 1.6 m
above the ground (away from direct
sunlight) in the air, buried in 5 cm
below the soil.
Photosynthetically active radiation
measurements The photosynthetic-
ally activeradiation sensor, which was
HOBO small automatic weather
station data logger (Onset Computer
Corporation, USA) in the canopies of
experimental plants was used to
measure the hotosynthetically active
radiation under full natural light and in
the two shading sheds. The measur-
ements were conducted every 10 s,
and the mean values were
automatically recorded every 10 min.
Relative chlorophyll content meas-
urements The portable chlorophyll
tester SPAD to-502 (Millipore, Japan)
was used to measure the SPAD count
values in the upper part of leaves to
represent the relative chlorophyll
content. Five plants were selected in
each processing gradient, and 3 -5
leaves from each plant were measur-
ed. The midribs of the leaves were
avoided from measuring. Each leave
was measured for 10 times, and the
average was taken. The measuring
times for the test was the May,
September of 2008 and May, Septem-
ber of 2009.
Determination of photosynthetic
parameters The open system of
portable infrared gas analyzer LI-6400
(LI-COR, USA) was used to determine
the light response curve. The light
intensity gradients were set to 2 000,
1 500, 1 000, 600, 300, 200, 100, 80,
50, 20 and 0 μmol/(m2·s). During the
measurements, the red and blue light
sources of the analyzer were used.
The leaf chamber temperature was 25
℃ with the flow rate of 500 μmol/s,
relative humidity of 50%. The test time
was the May, September of 2008 and
May, September of 2009. The light
response curve was determined in
clear day, and the stomatal conduct-
ance (Gs) was measured in the satur-
ated intensity of 1 500 μmol/(m2·s).
The measuring time was 7:00 -11:00
every day. For every treatment, five
mature leaves were randomly selected
and measured.
Data analysis One-WayANOVA
(Spss13.0) was used to analyze the
effects of different treatment gradients
on plant heights, ground diameters,
chlorophyll contents, gas exchange
parameters, light response curve
parameters of E. glasbripetalus; LSD
multiple comparison was used to test
the significances of the differences
between different radiative forcing
treatemtns. Pearson correlation analy-
sis was used to do the correlation
analysis; regression analysis was
used the stepwise multiple regression
analysis.
The light response curve was
plotted with the photosynthetically
active radiation (PAR) as abscissa, net
photosynthetic rate (Pn), intercellular
CO2 concentration (Ci), stomatal
conductance (Gs), transpiration rate
(Tr) as the vertical axis. Photosyn-
Assistant was used to fit the Pn-PAR
light response curve, obtaining the
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2012
A= φ·Q+Amax- (φ·Q+Amax)
2+4φ·Q·K·Q·Amax姨
2K -Rday
a-d, the daily PAR variation at different times; e, the seasonal PAR variation.
Fig.1 The daily and seasonal changes of phtosynthecially active radiation (PAR)
maximum net photosynthetic rate
(Amax), dark respiration rate (Rd), light
saturation point (LSP), light compen-
sation point (LCP), apparent quantum
efficiency (AQE). And then, SPSS13.
(SPSS Inc. USA) was used to process
and analyze the data. The equation for
light response curve fitted in the
PhotosynAssistant was as follows:
Where, A is the net photosyn-
thetic rate; Q is light intensity; φ is the
apparent quantum efficiency; K is the
curvature of the photosynthetic curve
with the size ranged from 0 to 1.
Results and Analysis
Daily and seasonal variation of
photosynthetically active radiation
(PAR)
As shown in Fig.1, radiative
forcing treatment reduced the amount
of photosynthetically active radiation.
The photosynthetically active radiation
of other treatments accounted for a
certain proportion of the photosyn-
thetically active radiation of the full
natural light, in which the weak
radiative forcing group accounted for
38% -40% of that of the full natural
light, while strong radiative forcing was
15% -17% of the full natural light
group. The annual variation of photos-
ynthetically active radiation showed
that the photosynthetically active
radiation shoed stable correlation in
different treatments that the photos-
ynthetically active radiation amount
reached the maximum around the
summer solstice, and then gradually
declined to the minimum in the winter
solstice, and then gradually increased.
Relative chlorophyll contents of
E. glasbripetalus in different radia-
tive forcing treatments
As shown in Fig.2, after one year
transplanting adaptive phase of
E . glasbripetalus seedlings, the mea-
sured data in May 2008 and
September 2009 showed that the
relative chlorophyll contents of E. glas-
bripetalus increased under the
radiative forcing. Compared with the
control, the weak radiative forcing
group increased relatively small, while
the strong radiative forcing group
increased greatly. There were seas-
onal variation of relative chlorophyll
contents between weak radiative
forcing group and the control that the
weak radiative forcing group had
higher relative chlorophyll contents
than the control in May 2008 and May
2009, but there was no significant
difference (P>0.05); the weak radiative
forcing group was higher than the
control in September 2008 and
September 2009, weak radiation, and
there were significant differences with
the control group (P<0.05), indicating
that after a sufficient sunlight, high
temperatures summer, the differences
in relative chlorophyll contents of E.
glasbripetalus between the control and
the weak radiative forcing group
increased. The strong radiative forcing
group showed significant differences
with the control in May, September
2008 and May, September 2009 (P<
0.05), indicating that strong radiative
forcing significantly increased the
relative chlorophyll contents of E.
glasbripetalus. The results showed
that E. glasbripetalus could response
to the effect of radiative forcing by
increasing the relative content of
chlorophyll.
Growth variation of E. glasbrip-
etalus in the different radiative
forcing treatments
As shown in Table 1, from May
2008 to September 2008, the average
increased ground diameter was as
follows: control group > weak radiative
forcing group> strong radiative forcing
group, and the increased tree heights
were: strong radiative forcing group >
weak radiative forcing group > control
group. The increased ground diam-
eters and plant heights between the
control and the strong radiative forcing
group showed significant difference
(P<0.05), indicating that in the growing
season from May to September with
sufficient light, radiative forcing inhibi-
ted the growth of ground diameter of
E. glasbripetalus, but promoted the
growth of tree height. From September
2008 to May 2009 and May 2009 to
September 2009, the increased
ground diameter continued the perfor-
mance from May 2008 to September
2008, i.e., control group > weak radia-
tive forcing group > strong radiative
forcing group, while there was no
significant rules for the increased tree
height. There was no significant
differences in increased ground dia-
meter and increased tree heights
between the treatments (P >0.05),
indicating that after more than 1 year
of radiation treatemtn, E. glasbri-
petalus showed a certain degree of
adaptability.
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Table 1 Seasonal variation of tree heights and ground diameter of E. sylvestris under different radiative forcing level (mean ± SE)
Date Year-Month Treatment Grounddiameter∥cm Tree height∥cm
Increased ground
diameter//cm
Increased tree
height∥m
2008-05 Control 0.703±0.182 a 41.4±14.473 a
Weak radiative forcing 0.831±0.129 b 63.7±6.403 a
Strong radiative forcing 0.830±0.200 b 63.9±13.060 b
2008-09 Control 1.643±0.348 a 83.6±23.161 a 0.940±0.374 a 42.3±26.848 a
Weak radiative forcing 1.608±0.228 a 121.9±9.845 a 0.777±0.225 a 58.2±11.332 ab
Strong radiative forcing 1.361±0.355 b 136.8±41.449 b 0.530±0.443 b 72.7±44.708 b
2009-05 Control 3.021±0.827 a 145.8±29.921 a 1.379±0.593 a 62.2±27.811 a
Weak radiative forcing 2.877±0.484 a 179.7±18.484 b 1.269±0.364 a 57.8±14.548 a
Strong radiative forcing 2.517±0.827 a 205.3±51.404 c 1.156±0.523 a 69.8±22.397 a
2009-09 Control 3.434±0.819 a 155.7±29.384 a 0.413±0.412 a 9.9±12.145 a
Weak radiative forcing 3.144±0.605 ab 217.6±138.700 a 0.266±0.307 a 37.8±134.5 a
Strong radiative forcing 2.747±0.885 b 214.7±52.166 a 0.230±0.163 a 9.4±7.389 a
Different letters indicate significant differences at the level of P=0.05; the increased tree heights and ground diameters are the results
compared with the last measurements.
Photosynthetic characteristics of
E. glasbripetalus in the different
radiative forcing treatments
Photosynthesis-light response
curve of E. glasbripetalus under
different radiative forcing As
shown in Fig.3, in the early summer of
May 2008 and May 2009, the
photosynthetic rates (Pn) of E. glasbr-
ipetalus in different treatments were
almost the same (Fig.3 A, C). Compar-
ed with the early summer, the respon-
ses of photosynthetic capacities to
radiative forcing of E. glasbripetalus in
the early autumn (September 2008
and September 2009) were much
more significant (Fig.3 B, D), indicating
that the radiative forcing show some
seasonal impact on the photosynthetic
capacity of E. glasbripetalus. When
photosynthetically active radiation was
greater than 600 μmol/(m2·s), in the
early spring and early summer of 2008
and 2009, the Pn of the control group
all had the highest values, while Pn of
the strong radiative forcing group was
the lowest, indicating that in larger
photosynthetically active radiation, the
control group had greater photos-
ynthetic capacity, while radiative
forcing reduced the photosynthetic
capacity of E. glasbripetalus. In
September 2008 and September
2009, under the strong radiative
forcing, the maximum net photosy-
nthetic rate (Amax) of E. glasbripetalus
decreased significantly (Fig.3 B, D),
which showed significant differences
with the control and weak radiation
forcing (P <0.05), indicating that the
strong radiation forcing had greater
impact on the photosynthetic capacity
of E. glasbripetalus.
Photosynthesis-light response
curve characteristic parameters of
E. glasbripetalus under different
radiative forcing levels As shown
in Table 2, under strong radiative
forcing, the light compensation point
(LCP), light saturation point (LSP) of
E. glasbripetalus and the maximum
net photosynthetic rate (Amax) were all
lower than the control group. Except
September 2009, the LCP of the
control and the strong radiative forcing
group showed significant differences in
other months (P<0.05); the LSP of the
strong radiative forcing group and the
control showed significant differences
(P<0.05) in May 2008 and September
Different letters above the bars indicate sig-
nificant differences at the level of P=0.05.
Fig.2 Annual variation of chlorophyll relative
content in E. sylvestris under different
radiative forcing level (mean ± SE)
A, B, C, D, the photosynthesis-response curves of E. sylvestris under different radiative
forcing levels in May 2008, September 2008, May 2009 and September 2009.
Fig.3 Photosynthesis-light response curves of E. sylvestris under different radiative forcing
levels
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2012
Different letters above the bars indicate significant differences at the level of P=0.05.
Fig.4 Annual variation of stomatal conductance (Gs) and transpiration rate (Tr) of E. sylvestris
underdifferent radiative forcing levels (mean±SE)
Table 2 Characteristic parameter values of the photosynthesis-light response curves of E. sylvestris under different radiative forcing levels
(mean ± SE) (P= 0.05)
Date Year-Month Treatment LCP∥μmol/m2·s LSP∥μmol/m2·s Amax∥μmol/m2·s AQY∥μmol/m2·s Rd∥μmol/m2·s
2008-05 Control 35.20±2.94 a 1244±61.42 a 13.44±0.65 a 0.051±0.002 3 a -1.67±0.088 a
Weak 25.33±2.66 b 762.67±17.02 b 10.84±0.36 b 0.056±0.001 3 a -1.35±0.129 a
Strong 15.20±0.80 c 1037.60±36.41 c 11.95±0.46 b 0.067±0.002 1 b -0.99±0.089 b
2008-09 Control 21.33±2.46 a 1762.00±36.47 a 19.85±0.36 a 0.081±0.002 4 ab -1.58±0.181 a
Weak 14.40±1.60 b 1466.40±116.46 b 15.57±0.62 b 0.073±0.004 4 a -0.96±0.039 b
Strong 8.00±2.53 b 875.20±42.17 c 10.92±0.27 c 0.101±0.011 3 b -1.11±0.131 b
2009-05 Control 64.80±1.50 a 1049.60±66.67 a 12.26±0.75 a 0.067±0.002 8 a -3.69±0.150 a
Weak 60.80±2.939 a 958.40±72.59 a 10.16±0.54 b 0.067±0.002 2 a -3.09±0.085 b
Strong 28.00±2.191 b 852.00±58.59 a 9.84±0.59 b 0.071±0.001 3 a -1.81±0.091 c
2009-09 Control 8.00±2.19 a 1079.20±123.33 a 15.15±0.69 a 0.072±0.003 1 a -0.52±0.144 a
Weak 12.81±4.08 a 1231.20±159.28 a 14.19±0.62 a 0.064±0.002 4 a -0.78±0.199 a
Strong 12.80±1.50 a 825.60±127.59 a 10.99±0.71 b 0.064±0.002 8 a -0.81±0.075 a
Different letters indicate significant differences at the level of P=0.05; AQY, apparent quantum yield; LCP, light compensation point; Amax,
maximum net photosynthetic rate; LSP, light saturation point; Rd, dark respiration rate.
Table 3 Correlation analysis of photosynthetic parameters and environmental factor of E. sylvestris under different radiative forcing levels
Photosynthetic parameter and
environmental factor Chlorophyll relative content Pn∥μmol/m
2·s Gs∥mol/m2·s PAR∥μmol/m2·s AT∥℃ RH∥%
Chlorophyll relative content 1
Pn∥μmol/m2·s 0.691 382** 1
Gs∥mol/m2·s 0.274 587* 0.272 503* 1
PAR∥μmol/m2·s -0.650 720** -0.287 570* -0.468 31** 1
AT∥℃ -0.121 520 0.075 804 -0.17688 0.314 519* 1
RH∥% 0.516 578** 0.549 571** -0.055 29 -0.353 740** -0.417 45** 1
*, correlation is significant at the level of 0.05 (2-tailed);**, correlation is significant at the level of 0.01 (2-tailed). Pn, net photosynthetic
rate; Gs, stomatal conductance; PAR, photosynthetically active radiation; AT, air temperature; RH, relative air humidity.
2008; the Amax of the strong radiative
forcing group and the control showed
significant differences (P<0.05) in May
2008, September 2008, May 2009 and
September 2009, indicating that under
radiative forcing, with the reduction of
light energy used by E. glasbripetalus,
the effect of strong radiative forcing
became more significant. During the
experimental period, the apparent
quantum yield (AQY) showed no
significant change rule. The dark
respiration rate (Rd) of the strong
radiative forcing group and the control
group showed significant difference
(P <0.05) in May 2008, September
2008 and May 2009, while there was
no significant difference in Rd between
the strong radiative forcing group,
weak radiative forcing group and the
control group in September 2009
(P>0.05).
Stomatal conductance (Gs) and
transpiration rate (Tr) of E. glas-
bripetalus in the different radiative
forcing levels As shown in Fig.4, in
September 2008, May and September
2009, the Gs of E. glasbripetalus of the
control group was the largest, showing
significant difference with the strong
radiative forcing treatment (P<0.05); in
May and September 2008, September
2009, the Gs of E. glasbripetalus of the
weak radiative forcing group was
greater than the strong radiative
forcing group, and showed significant
difference (P <0.05); in May and
September 2008, May and September
2009, the Gs of E. glasbripetalus was
the smallest in the strong radiative
forcing treatment. Under the strong
radiative forcing treatment, the Tr of E.
glasbripetalus was the minimum, and
the Tr of E. glasbripetalus of the strong
radiative forcing group and the control
showed significant differences in May
and September 2008, May 2009 (P<
0.05), indicating that strong radiative
forcing reduced the transpiration rate
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of Tr of E. glasbripetalus. In early
summer (May 2008 and May 2009),
the Tr of weak radiative forcing group
was smaller than that of the control
group, and showed significant differ-
ence with the control (P<0.05), while in
early autumn (September 2008 and
September 2009), the Tr of weak
radiative forcing group was greater
than that of the control group, and
showed significant difference with the
control (P<0.05), indicating that there
were seasonal variations in the effect
of weak radiative forcing on the
transpiration rate of E. glasbripetalus.
Correlation analysis of photosyn-
thetic parameters and environ-
mental factor of E. sylvestris under
different radiative forcing levels
As shown in Table 3, there were
extremely significant positive correla-
tion between the relative chlorophyll
content, photosynthetic rate Pn and
relative humidity of air, indicating that
relative chlorophyll content, Pn and
relative humidity of air were closely
related; the relative humidity showed
extremely significant negative correla-
tion with PAR and air temper-ature,
but they were not closely related
(correlation coefficient greater than
-0.5), indicating that air humidity was
subject to the combined effect of
photosynthetically active radiation
(PAR) and air temperature. There was
significant positive correlation between
air temperature and PAR, but not
closely correlated (correlation coeffici-
ents less than 0.5), indicating that air
temperature was subject to the effect
of photosynthetically active radiation
(PAR). There was no significant
correlation between air temperature
and photosynthetic parameters. There
was significant negative correlation
between PAR and Pn, and PAR
showed extremely significant negative
correlation with relative chlorophyll
content, photosynthetic rate (Pn), in-
dicating that photosynthetically active
radiation PAR was an important factor
in influencing relative chlorophyll
content, photosynthetic rate (Pn) and
stomatic conductance. Stomatic cond-
uctance presented significant positive
correlation with the relative chlorophyll
content, photosynthetic rate, but not
closely correlated (correlation coeffici-
ent of less than 0.3). Photosynthetic
rate (Pn) and relative chlorophyll cont-
ent showed extremely significant posi-
tive correlation (correlation coefficient
of 0.691), indicating that the relative
chlorophyll content was an important
factor in influencing the photosynthetic
rate (Pn).
Discussion
Chlorophyll is an extremely
important biomolecule, critical in
photosynthesis, which allows plants to
absorb energy from light [11]. According
to the data analysis, after 1 year
transplanting adaptive period of E. gla-
sbripetalus seedlings, the relative
chlorophyll content of E. glasbripetalus
was: strong radiative forcing group >
weak radiative forcing group > control
group. The chlorophyll content showed
significant negative correlation with
photosynthetically active radiation
(PAR). The chlorophyll content was
higher in the appropriate shade leaves
than the full exposure ones. Some
studies show that this is because in full
exposure conditions, the excess light
energy absorbed by the leaves makes
part of the excited chlorophyll could
not timely be quenched by excitation
energy transfer and photochemical
reactions, and reacted with molecular
oxygen in the environment, generating
singlet oxygen, causing chlorophyll
bleaching, thereby decreasing the
chlorophyll content[12-13]. Increasing chlo-
rophyll content can increase the
absorption of light energy by E. glas-
bripetalus in light weakening conditi-
ons[14-15]. The reduction of Pn is subject
to stomatal limitation and non-stomatal
limitation, and when Pn and Gs are
consistent, the reduction of Pn is
mainly caused by Gs; non-stomatal
limitation is mainly due to reduced
carboxylation capacity of mesophyll
cells[16]. In this experiment, we find that
there is significant correlation between
Pn and Gs, but the correlation
coefficient is not high, indicating that
under radiative forcing, the reduction
of Pn of E. glasbripetalus seedlings is
subject to both stomatal limitation and
non-stomatal limitation. It has shown
that radiative forcing siginificantly
reduce the Amax, LCP, LSP of E. glas-
bripetalus leaves, indicating that
radiaive forcing can increase the
utilization efficiency of E. glasbrip-
etalus to weak light, reduce the
utilization efficiency of strong light,
while narrowing the utilization scope of
light energy, which is similar to other
environmental stress test on plant
responses[17]. In addition, radiative fo-
rcing and seasonal factors all have
significant impact on Pn, Gs, Tr and
relative chlorophyll content of E. glas-
bripetalus. On the whole, radiative
forcing can directly change solar radia-
tion amount, resulting in effect on
temperature and relative humidity,
which can affect the morphology,
structure, physiological and bioche-
mical aspects of E. glasbripetalus.
Studies have shown that with the
extending stress time, the adaptive
ability to outer environment in the
plants is also incrased[18-20]. After more
than 2 years of radiative forcing
treatment, E. glasbripetalu gradually
adapted to weak light environment,
and there is no significant difference in
increased tree height and increased
ground diameter between the groups
(P>0.05).
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1245
Agricultural Science & Technology
Agricultural Science & Technology Vol.13, No.6, 2012
2012
辐射强迫对秃瓣杜英生长和光合生理的影响
杨爽，江 洪 *，翟秀丽 （浙江农林大学浙江省森林生态系统碳循环与固碳减排重点实验室，浙江杭州 311300）
摘 要 [目的]通过对辐射强迫下亚热带典型树种秃瓣杜英幼苗的生长及光合生理的研究，初步探讨植物对于辐射强迫的生理响应及适应性机
理，进而揭示辐射变化对亚热带森林树种的影响。[方法]试验设置 3个处理水平，即对照组（100%自然光）、弱辐射强迫（39%自然光）、强辐射强迫
（16%自然光），对秃瓣杜英不同时期的叶绿素相对含量、光合作用参数等进行测定，分析不同处理梯度对秃瓣杜英株高、地径、叶绿素含量、气体
交换参数、光响应曲线参数的影响。[结果]不同处理下秃瓣杜英的地径生长量为：对照组>弱辐射强迫组>强辐射强迫组，株高生长量在处理前期
为：强辐射强迫组>弱辐射强迫组>对照组，在处理后期无明显变化规律；叶绿素相对含量表现为：强辐射强迫>强弱辐射强迫>对照组，辐射强迫处
理下，秃瓣杜英的光补偿点(LCP)、光饱和点(LSP)和最大净光合速率（Amax）均降低，强辐射强迫处理下，秃瓣杜英的气孔导度（Gs）、蒸腾速率（Tr）显
著小于对照组；表观光量子效率(AQY)和暗呼吸速率（Rd）变化规律不明显。[结论]综合来说，辐射强迫引起环境因子的变化，对秃瓣杜英的地径和
株高生长量、叶绿素相对含量、光合生理参数有显著影响，但随着秃瓣杜英逐渐适应了这种变化，后期其对地径和株高增量的影响不显著，表明秃
瓣杜英能一定程度上适应这种辐射强迫环境，在一定时期内生长正常。
关键词 辐射强迫；秃瓣杜英；叶绿素相对含量；光合特征
基金项目 科技部重大国际合作项目（20073819）；国家高技术研究发展计划项目 (2009AA122001，2009AA122005)；科技部重大基础性项目
（2007FY110300-08）；国家重点基础研究发展规划项目(2010CB950702，2010CB428503)；国家自然科学基金项目(40671132)；浙江省重
大科技专项（2008C13G2100010）。
作者简介 杨爽(1986-)，男,四川绵阳人，硕士研究生，研究方向:全球变化生态学，E-mail: sndqqyangshuang@163.com。*通讯作者，教授，博士生导
师，从事生态系统生态学及全球变化生态学等方面的研究，E-mail: jianghong_china@hotmail.com。
收稿日期 2012-02-28 修回日期 2012-04-16
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Responsible editor: Na LI Responsible proofreader: Xiaoyan WU
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