- Email: [email protected]
Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
September 2012
ScienceDirect
Vol. 19 No. 3 14-19
Journal of Northeast Agricultural University (English Edition)
Available online at www.sciencedirect.com
Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels Li Da-yong1, Zhang Zhi-an1*, Zheng Dian-jun1, 2, Jiang Li-yan2, and Wang Yuan-li2 1
College of Agronomy, Jilin Agricultural University, Changchun 130118, China
2
Liaoyuan Academy of Agricultural Sciences, Liaoyuan 136200, Liaoning, China
Abstract: A total of nine soybean (Glycine max (L.) Merr.) cultivars were divided into three yield levels which were planted under the same environmental condition. The net photosynthetic rate was measured by LI-6400 portable photosynthesis system. The chlorophyll content and specific leaf weight were measured with regular methods. The results showed that the specific leaf weight, chlorophyll content and net photosynthetic rate of high yield varieties were higher than those of low yield varieties. The yield had a significantly positive correlation with the net photosynthetic rate. With the improvement of modern technology, the net photosynthetic rate could be measured quickly and exactly. Hence, net photosynthetic rate could be used as an effective index in the selection of high yield soybean. Key words: soybean, yield, net photosynthetic rate, specific leaf weight, chlorophyll content CLC number: S565.1
Document code: A
Article ID: 1006-8104(2012)-03-0014-06
logical structures and physiological traits (Xu et al.,
Introduction
1995; Li et al., 1999; Yang et al., 2008; Gao et al.,
90%-95% of dry matter in over ground part of plant
relationships between yield and specific leaf weight,
comes from photosynthesis. Theoretically, the
chlorophyll content as well as net photosynthetic rate
maximum solar radiation utilization rate of crops is
(Wang et al., 2004; Pearce et al., 1969). The studies
5%-6%. However, the actually average solar energy
on the leaves of soybean, sunflower and ginseng
utilization rate at present is only 1%, only some
demonstrated that crop yield was closely related to
individual species reach 3.5%, indicating crops have a
the leaf specific leaf weight, content of soluble
broad space potential to increase yield (Mann, 1999).
sugar and net photosynthetic rate (Xu et al., 2003; Xu
The key for the implementation of yield increasing is
et al., 1994). However, systematic researches on the
enhancing the solar energy utilization efficiency of
changes of specific leaf weight, chlorophyll content
the crops, while increasing photosynthetic capacity
and net photosynthetic rate at different growth stages
is the fundamental way to enhance the solar energy
of soybean with different yield levels are not many.
utilization efficiency.
In the present study, the changes of specific leaf
Photosynthesis mainly takes place in plant leaves.
weight, chlorophyll content and net photosynthetic
The yields of crops are related to the leaf morpho-
rate in the leaves of soybean with different yield levels
2009). Previous studies indicated that there were close
Received 23 June 2010 Supported by the National Natural Science Foundation of China (30871547); Foundation of Department of Education of Jilin Province (2006041); Scientific Research Foundation of Jilin Agricultural University (2009028) Li Da-yong (1977-), male, Ph. D candidate, engineer, engaged in the research of soybean physiology and ecology. * Corresponding author. Zhang Zhi-an, professor, engaged in the research of crop physiology and ecology. E-mail: [email protected] E-mail: [email protected]
·15·
Li Da-yong et al. Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
at different growth stages and their relationships
was used to measure the specific leaf weight, chloro-
with yield were studied, aiming at providing some
phyll content and net photosynthetic rate. Specific
theoretical foundations for the high-yield breeding of
leaf weight was measured using punching, drying
soybean.
and weighing method (Zhang and Zhang, 2006).
Chlorophyll content was determined by spectro-
Materials and Methods
photometry (Zhang and Zhang, 2006). Net photo-
Materials
compound leaf was measured by LI-6400 portable
The studied nine soybean (Glycine max (L.) Merr.)
photosynthesis system.
synthetic rate (Pn) of the middle leaves in the ternately
cultivars were medium maturity varieties with the same maturity period, which were provided by the Soybean Germplasm Resources Room of Jilin
Results
Academy of Agricultural Sciences and the Innovation
Yield comparison of three soybean varieties
Center of Jilin Province Soybean Region Technology,
with different yield levels
Jilin Agricultural University. Low yield varieties:
As can be seen in Table 1, there was distinct diffe-
Jinyuan No.1, Jiti No.5 and Jilin No.5; middle yield
rence in the yields among different soybean varieties
varieties: Jilin No.9, Jilin No.15 and Jilin No.26; high
with three yield levels. The mean yield of high yield
yield varieties: Jinong No.7, Jinong No.16 and Jiyu
varieties was respectively 25.9% and 65.1% higher
No.66.
than those of middle yield and low yield varieties, and the difference was extremely significant (P<0.01). The
Methods
mean yield of middle yield varieties was 31.2% higher
Experimental design
than that of low yield varieties, and the difference was
Experiments were carried out in the experimental
also extremely significant (P<0.01).
station of Jilin Agricultural University during 20082009 employing randomized block design with 5 row plots. The row spacing was 0.65 m; the row length was 5 m; the area of each plot was 16.25 m2, with three replicates. The soybean seeds were sowed on 28 April,
Table 1 Significant analysis of yield difference Yield level
the density was 200 000 plants per hectare. Final singling was completed during seedling stage for all
High yield
varieties and normal field management was adopted. threshing, air drying and cleaning were conducted Middle yield
rows subtracting 50 cm of both ends of each row was Test methods the fourth leaf counting from the top of the plant at V4 (the third compound leaf in stem was completely developed), R 2 (flowering stage), R 4 (pod bearing stage), R6 (seed filling stage) and R7 (maturity stage)
Jinong No.7
2 328.9±16.5
Jinong No. 16
2 429.5±15.8
Jiyu No.66
2 352.1±18.3
Low yield
2 370.2±52.7Aa
Jilin No.9
1 916.6±20.5
Jilin No.15
1 834.9±16.2
Jilin No.26
1 898.4±17.2
Mean
taken as plot yield. According to the Fehr grading standards (Sun, 2005),
Yield (kg • hm-2)
Mean
The soybean was harvested on 27 September, uniformly. The soybean seed yield of the middle three
Variety
1 883.3±42.9Bb
Jinyuan No.1
1 382.9±13.2
Jiti No.5
1 418.1±12.5
Jilin No.5
1 506.7±14.3
Mean
1 435.9±63.8Cc
Capital letters mean extremely significant difference at 0.01 level, and small letters mean significant difference at 0.05 level.
http: //publish.neau.edu.cn
·16·
Journal of Northeast Agricultural University (English Edition)
Vol. 19 No. 3 2012
difference at the flowering stage was the biggest, the Changes of specific leaf weight in leaves of
value of high yield varieties was 23.3% higher than that
soybean with different yield levels at different
of low yield varieties. The difference at the seedling stage
growth stages
was smaller; the specific leaf weight of high yield varie-
From Fig. 1, we can see that the specific leaf weights
ties was 5.9% higher than that of low yield varieties.
of soybean varieties with different yield levels at different growth stages showed different changes,
Changes of chlorophyll content in leaves of
appearing a trend of first declining and then increasing
soybean with different yield levels at different
from seedling stage to maturity stage. The minimum
growth stages
value and maximum value appeared at the flowering
Fig. 2 showed that the chlorophyll content in the
stage and seed filling stage, respectively.
leaves of high yield varieties was higher than that in
Specific leaf weight (mg • dm-2)
the middle yield and low yield varieties. At the seed 700 650 600
550 500 450 400
of high yield varieties was 14.5% and 20.2% higher
V4
R2
than that in the middle yield and low yield varieties, respectively. At the maturity stage, the chlorophyll content in the leaves of high yield varieties was 10.6% and 26.8% higher than that in the middle yield and low
350 300
filling stage, the chlorophyll content in the leaves
Low yield cultivars Middle yield cultivars High yield cultivars
yield varieties, respectively. At the late growth stage, R4
R6
R7
Stage of growth
Fig. 1 Changes of specific leaf weight in leaves of soybean at different growth stages
the difference in chlorophyll content between the leaves of high yield and low yield varieties gradually became bigger. The chlorophyll contents in high yield varieties stayed at higher levels, indicating the slow down of aging, which laid the foundation for the
The specific leaf weights of varieties with higher
enhancement of photosynthesis.
growth stage. Among them, the biggest difference in specific leaf weight between high yield and middle yield varieties appeared at the seed filling stage, the value of high yield varieties was 5.7% higher than that of middle yield varieties. The difference at the maturity stage was the smallest, and the specific leaf weight of high yield varieties was 1.1% higher than that of middle yield varieties. The biggest difference in
Chlorophyll content (mg • dm-2)
yields were higher than those with lower yields at each 8 7 6 5
Low yield cultivars Middle yield cultivars High yield cultivars
4 3 2
V4
specific leaf weight between middle yield and low yield varieties appeared at the flowering stage, and the value of middle yield varieties was 3.9% higher than
R2
R4
R6
R7
Stage of growth
Fig. 2 Changes of chlorophyll content in leaves of soybean at different growth stages
that of low yield varieties. The difference at the seed filling stage was the smallest; the specific leaf weight
Changes of net photosynthetic rate in leaves
of middle yield varieties was only 0.1% higher than
of soybean with different yield levels at diffe-
that of low yield varieties. Comparing the specific leaf
rent growth stages
weights between high yield and low yield varieties, the
The net photosynthetic rates in leaves of soybean
E-mail: [email protected]
·17·
Li Da-yong et al. Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
varieties with three different yield levels were the
specific leaf weight, but did not reach significant level.
highest in high yield varieties, followed by middle yield varieties, and the lowest in low yield varieties at each growth stage (Fig. 3). During the whole growth stage, the net photosynthetic rates for each
Table 2 Relationships between soybean yield and specific leaf weight, chlorophyll content as well as net photosynthetic rate in soybean leaves at different growth stages
individual yield level variety slowly increased from the seedling stage, reached the peak values at the pod
Item
bearing stage, then declined, and finally reached the
Specific leaf
minimum values at the maturity stage. At the seedling,
weight
flowering, pod bearing, seed filling and maturity
Chlorophyll
stages, the net photosynthetic rates of high yield varieties were respectively 18.6%, 22.0%, 32.0%, 18.9% and 57.3% higher than those of low yield varieties, the difference was significant (P<0.05). At the seed filling and maturity stages, the net photosynthetic
content Net photosynthetic rate
V4
R2
R4
R6
R7
0.3008
0.6528*
0.2322
0.1556
0.8390**
0.2530
0.6383*
0.5733
0.5690
0.8602**
0.6187
0.7725
0.8683**
0.6694*
0.8573**
* and ** mean significant differences at 0.05 and 0.01 levels, respectively.
rates of high yield varieties were respectively 12.4% and 32.8% higher than those of middle yield varieties, the
At the flowering and maturity stages, the yield had
difference was significant (P<0.05). The enhancement
significantly positive correlations with the chlorophyll
of net photosynthetic rate in high yield varieties de-
content. Especially in maturity stage, the positive
monstrated their better substance synthesis capacity,
correlation was extremely significant (r=0.8602**). At
which laid the foundation for yield increase.
seedling, pod bearing and seed filling stages, the positive correlations between yield and chlorophyll con-
Pn (µmol • m-2• s-1)
35
tent were not significant (r=0.2530, 0.5733 and 0.5690).
30 25 20 15 10 5 0
There were significantly or extremely significantly
Low yield cultivars Middle yield cultivars High yield cultivars V4
R2
R4
positive correlations between soybean yield and net
photosynthetic rate at the flowering, pod bearing, seed
R6
R7
Stage of growth
filling and maturity stages (r=0.7725**, 0.8683**, 0.6694* and 0.8573**). At the seedling stage, the positive correlations between yield and net photosynthetic rate did not reach significant level (r=0.6187).
Fig. 3 Changes of net photosynthetic rate in soybean leaves at different growth stages
Discussion
Relationships between soybean yield and
Chlorophyll is the basic substance for leaves to absorb,
specific leaf weight, chlorophyll content as well
transfer and convert light energy. Hence, chlorophyll
as net photosynthetic rate in soybean leaves
content is closely related to the leaf photosynthetic rate
As can be seen from Table 2, the yield had signi-
(Zhang et al., 1986). The results in the present study
ficantly and extremely significantly positive correla-
demonstrated the chlorophyll content in the leaves of
tions with the specific leaf weight in soybean leaves
high yield soybean varieties appeared an increasing
at the flowering and maturity stages (r=0.6528* and
trend as compared with that of low yield varieties. The
0.8390**). At seedling, pod bearing and seed filling
soybean yield had a significantly positive correlation
stages, the yield had positive correlations with the
with the chlorophyll content in the leaves at the http: //publish.neau.edu.cn
·18·
Journal of Northeast Agricultural University (English Edition)
Vol. 19 No. 3 2012
flowering and maturity stages, indicating that the
correlation was significant. The research results
increasing of chlorophyll content in the leaves of high
of Singh et al. (1993) demonstrated that yield was
yield varieties laid the foundation for the enhancement
positively correlated with the net photosynthetic
of photosynthetic rate and yield increase.
rate at flowering and filling stages. Wells et al.
Specific leaf weight is an important index of
(1982) considered soybean seed yield had a positive
leaf morphology and physiological traits. Owing to
correlation with apparent canopy photosynthesis curve
the simple and exact determination method, it is com-
at pod bearing and physiological maturity stages.
monly used for the comparative determination among
Du et al. (1999) pointed out that soybean yield was
varieties or strains (Gan et al., 1998). Specific leaf
positively correlated with photosynthetic rate at R 4
weight is also an index of source strength, which
stage. Zhou et al. (1990) also considered soybean seed
has close relationship to sink strength. The higher
yield had a significantly positive correlation with the
specific leaf weight and its longer duration are the
leaf photosynthetic rate at pod bearing and seed filling
performances of higher source strength. McClendon
stages (r=0.88**). Xu and Shen (1992) considered
(1962) and Orgren (1977) demonstrated that soybean
the negative correlation between yield and leaf
specific leaf weight was closely related to photo-
photosynthetic was a false appearance. Xu (1999) also
synthetic rate.
pointed out 95% of the plant dry matter came from
The present study showed that the specific leaf
assimilated CO2 by photosynthesis. This basic fact
weight in leaves of high yield soybean varieties was
determined the positive correlation between crop yield
the highest, followed by middle varieties, the low
and leaf photosynthetic rate, neither no correlation
yield varieties were the lowest. The soybean yield had
nor negative correlation. The positive correlations
significantly positive correlations with the specific leaf
were not a few exceptions but regular performance.
weight at the flowering and maturity stages, indicating
This internal positive correlation might be covered by
that the increasing of specific leaf weight in the leaves
the complex changes of other factors, for example,
of high yield varieties also laid the foundation for the
the yield of species with high leaf photosynthetic
enhancement of photosynthetic rate and yield increase.
rate might be lower than that of species with low
Zhang et al. (1986) pointed out that the yield was
leaf photosynthetic rate but large leaf area and long
positively correlated with the mean photosynthetic rate
photosynthesis functional period because of its small
at the main growth stage for each soybean variety, the
leaf area and short photosynthesis functional period.
correlation coefficient r was 0.8592, this trend could
The results in the present study indicated that
be maintained in different years. Evans and Rawson
there were significantly or extremely significantly
(1970) considered there was no stable correlation
positive correlations between soybean yield and net
between leaf photosynthetic rate of crops and
photosynthetic rate at the flowering, pod bearing,
productivity. Dong et al. (1979) studied eight soybean
seed filling and maturity stages. At the seedling
varieties and pointed out that mean net photosynthetic
stage, the positive correlation between yield and net
rate was obviously correlated with neither biological
photosynthetic rate did not reach significant level
yield nor economic yield.
(r=0.6187). The results were basically in accordance
Leaf photosynthesis is a dynamic process, which
with those of Zhang et al. (1986) and Xu et al (1999).
changes along with the growth stages (Patterson and Hoss, 1980). The study of Chu et al. (1988) indicated yield was positively correlated with net assimilation
Conclusions
rate at the early and middle growth stages, while
The specific leaf weight, chlorophyll content and net
negatively correlated at the late growth stage, no
photosynthetic rate of high yield soybean varieties
E-mail: [email protected]
·19·
Li Da-yong et al. Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
were higher than those of low yield varieties. The yield of soybean had significantly positive correlations with the specific leaf weight, chlorophyll content and net photosynthetic rate. Among them, the correlation between yield and net photosynthetic rate was closer
London. pp. 721-733. Patterson T G, Hoss D N. 1980. Enzymatic changes during the senescence of field-grown wheat. Crop Science, 20: 19-23. Pearce R B, Carlson G E, Barn S D K. 1969. Specific leaf weight and photosynthesis in alfalfas. Crop Science, 9: 423-426.
than those between yield and specific leaf weight as
Singh S P, Lal K B, Ram R S, et al. 1993. Photosynthetic efficiency
well as chlorophyll content. With the improvement
and productivity of pigeonpea. Indian Journal of Pulses Research, 6:
of modern technology, the net photosynthetic rate
212-214.
could be measured quickly and exactly. Hence, net photosynthetic rate could be used as an effective index in the selection of high yield soybean, which could reduce breeding blindness.
Sun H. 2005. Jilin Soybean. Jilin Science and Technology Press, Changchun. pp. 124-125. Wang J A, Ning H L, Luo Q X, et al. 2004. The content of chlorophyll, the activity of RUBP and Hill and their correlations with yield . Journal of Northeast Agricultural University, 35(2): 129-134.
References Chu K X. 1988. Study on models of regulations of relationships between leaf area alteration, leaf area duration and net assimilation rate with high yield of soybean. Soybean Science, 7(3): 215-222. Dong Z, Bin Y Q, Sun L Q. 1979. Comparative study on the productivity of soybean variety. Journal of Shenyang Agricultural College, 1: 37-47. Du W G, Zhang G R, Man W Q, et al. 1999. Study on relationship between soybean photosynthesis and yield. Soybean Science, 18(2): 154-159. Evans L T, Rawson H M. l970. Photosynthesis and respiration by the flag leaf and components of the ear during grain development in wheat. Australian Journal of Biological Sciences, 23(2): 245-254. Gan Y B, Tu X W, Tian R J. 1998. Study on optium timing of nitrogen application on soybean. Soybean Science, 17(4): 287-291. Gao L, Liu L J, Dong S K, et al. 2009. Effect of drought stress on physiological and biochemical characteristics in leaves of soybean seedlings. Journal of Northeast Agricultural University, 40(8): 1-4. Li M Y, Liu L J, Zu W, et al. 1999. The relationship between dry matter accumulation and yield among different genotypes of soybean. Journal of Northeast Agricultural University, 30(4): 324-328. Mann C C. 1999. Genetic engineers aim to soup up crop photosynthesis. Science, 283(5400): 314-316. McClendon J H. 1962. The relationship between the thickness of deciduous leaves and their maximum photosynthetic rate. American Journal of Botany, 49(4): 320-322. Orgren W L. 1977. Increasing carbon fication by crop plants. In: Proceeding of the 4th International Conference on Photosynthesis.
Wells R, Schulze L L, Ashley D A. 1982. Cultivar differences in canopy apparent photosynthesis and their relationship to seed yield in soybeans. Crop Science, 22: 886-890. Xu D Q. 1999. Photosynthetic rate, photosynthetic efficiency and crop yield. Bulletin of Botany, 34(8): 8-10. Xu D Q, Shen Y G. 1992. Photosynthesis and crop yield. In: Zou Q, Wang X C. Physiology advances in high yield and high efficiency of crop. Science Press, Beijing. pp. 87-90. Xu H F, Liu X T, Jin Y M, et al. 2003. Study on sunflower chlorophyll and the specific leaf weight. System Sciences and Comprehensive Studies in Agriculture, 19(2): 97-100. Xu K Z, Kuroda E, Hirano M. 1995. The dynamic changes of nitrogen content and photosynthesis and their correlations in pot rice leaves after anthesis. Acta Agronomica Sinica, 21(2): 171-175. Xu K Z, Zhang Z A. 1994. Study on variability of spcific leaf weight in Panax Ginseng. Journal of Jilin Agricultural University, 16(4): 39-42. Yang Y, Cang J, Wang X D, et al. 2008. Photosynthetic characteristics of soybean pod and its contribution to yield. Journal of Northeast Agricultural University, 39(12): 51-56. Zhang Z A, Zhang M S. 2006. Techniques of Plant Physiological Experiment. Jilin University Press, Changchun. pp. 51-58, 80. Zhang Z X, Ma Z F, Zhao S W, et al. 1986. The relationship between net photosynthetic rate and yield formation in soybean. Acta Agronomica Sinica, 12(1): 43-48. Zou D S, Zheng P Y. 1990. Comparative studies on main physiological characters of leaves among 25 varieties in soybean. Soybean Science, 9(1): 25-32.
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ScienceDirect
Vol. 19 No. 3 14-19
Journal of Northeast Agricultural University (English Edition)
Available online at www.sciencedirect.com
Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels Li Da-yong1, Zhang Zhi-an1*, Zheng Dian-jun1, 2, Jiang Li-yan2, and Wang Yuan-li2 1
College of Agronomy, Jilin Agricultural University, Changchun 130118, China
2
Liaoyuan Academy of Agricultural Sciences, Liaoyuan 136200, Liaoning, China
Abstract: A total of nine soybean (Glycine max (L.) Merr.) cultivars were divided into three yield levels which were planted under the same environmental condition. The net photosynthetic rate was measured by LI-6400 portable photosynthesis system. The chlorophyll content and specific leaf weight were measured with regular methods. The results showed that the specific leaf weight, chlorophyll content and net photosynthetic rate of high yield varieties were higher than those of low yield varieties. The yield had a significantly positive correlation with the net photosynthetic rate. With the improvement of modern technology, the net photosynthetic rate could be measured quickly and exactly. Hence, net photosynthetic rate could be used as an effective index in the selection of high yield soybean. Key words: soybean, yield, net photosynthetic rate, specific leaf weight, chlorophyll content CLC number: S565.1
Document code: A
Article ID: 1006-8104(2012)-03-0014-06
logical structures and physiological traits (Xu et al.,
Introduction
1995; Li et al., 1999; Yang et al., 2008; Gao et al.,
90%-95% of dry matter in over ground part of plant
relationships between yield and specific leaf weight,
comes from photosynthesis. Theoretically, the
chlorophyll content as well as net photosynthetic rate
maximum solar radiation utilization rate of crops is
(Wang et al., 2004; Pearce et al., 1969). The studies
5%-6%. However, the actually average solar energy
on the leaves of soybean, sunflower and ginseng
utilization rate at present is only 1%, only some
demonstrated that crop yield was closely related to
individual species reach 3.5%, indicating crops have a
the leaf specific leaf weight, content of soluble
broad space potential to increase yield (Mann, 1999).
sugar and net photosynthetic rate (Xu et al., 2003; Xu
The key for the implementation of yield increasing is
et al., 1994). However, systematic researches on the
enhancing the solar energy utilization efficiency of
changes of specific leaf weight, chlorophyll content
the crops, while increasing photosynthetic capacity
and net photosynthetic rate at different growth stages
is the fundamental way to enhance the solar energy
of soybean with different yield levels are not many.
utilization efficiency.
In the present study, the changes of specific leaf
Photosynthesis mainly takes place in plant leaves.
weight, chlorophyll content and net photosynthetic
The yields of crops are related to the leaf morpho-
rate in the leaves of soybean with different yield levels
2009). Previous studies indicated that there were close
Received 23 June 2010 Supported by the National Natural Science Foundation of China (30871547); Foundation of Department of Education of Jilin Province (2006041); Scientific Research Foundation of Jilin Agricultural University (2009028) Li Da-yong (1977-), male, Ph. D candidate, engineer, engaged in the research of soybean physiology and ecology. * Corresponding author. Zhang Zhi-an, professor, engaged in the research of crop physiology and ecology. E-mail: [email protected] E-mail: [email protected]
·15·
Li Da-yong et al. Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
at different growth stages and their relationships
was used to measure the specific leaf weight, chloro-
with yield were studied, aiming at providing some
phyll content and net photosynthetic rate. Specific
theoretical foundations for the high-yield breeding of
leaf weight was measured using punching, drying
soybean.
and weighing method (Zhang and Zhang, 2006).
Chlorophyll content was determined by spectro-
Materials and Methods
photometry (Zhang and Zhang, 2006). Net photo-
Materials
compound leaf was measured by LI-6400 portable
The studied nine soybean (Glycine max (L.) Merr.)
photosynthesis system.
synthetic rate (Pn) of the middle leaves in the ternately
cultivars were medium maturity varieties with the same maturity period, which were provided by the Soybean Germplasm Resources Room of Jilin
Results
Academy of Agricultural Sciences and the Innovation
Yield comparison of three soybean varieties
Center of Jilin Province Soybean Region Technology,
with different yield levels
Jilin Agricultural University. Low yield varieties:
As can be seen in Table 1, there was distinct diffe-
Jinyuan No.1, Jiti No.5 and Jilin No.5; middle yield
rence in the yields among different soybean varieties
varieties: Jilin No.9, Jilin No.15 and Jilin No.26; high
with three yield levels. The mean yield of high yield
yield varieties: Jinong No.7, Jinong No.16 and Jiyu
varieties was respectively 25.9% and 65.1% higher
No.66.
than those of middle yield and low yield varieties, and the difference was extremely significant (P<0.01). The
Methods
mean yield of middle yield varieties was 31.2% higher
Experimental design
than that of low yield varieties, and the difference was
Experiments were carried out in the experimental
also extremely significant (P<0.01).
station of Jilin Agricultural University during 20082009 employing randomized block design with 5 row plots. The row spacing was 0.65 m; the row length was 5 m; the area of each plot was 16.25 m2, with three replicates. The soybean seeds were sowed on 28 April,
Table 1 Significant analysis of yield difference Yield level
the density was 200 000 plants per hectare. Final singling was completed during seedling stage for all
High yield
varieties and normal field management was adopted. threshing, air drying and cleaning were conducted Middle yield
rows subtracting 50 cm of both ends of each row was Test methods the fourth leaf counting from the top of the plant at V4 (the third compound leaf in stem was completely developed), R 2 (flowering stage), R 4 (pod bearing stage), R6 (seed filling stage) and R7 (maturity stage)
Jinong No.7
2 328.9±16.5
Jinong No. 16
2 429.5±15.8
Jiyu No.66
2 352.1±18.3
Low yield
2 370.2±52.7Aa
Jilin No.9
1 916.6±20.5
Jilin No.15
1 834.9±16.2
Jilin No.26
1 898.4±17.2
Mean
taken as plot yield. According to the Fehr grading standards (Sun, 2005),
Yield (kg • hm-2)
Mean
The soybean was harvested on 27 September, uniformly. The soybean seed yield of the middle three
Variety
1 883.3±42.9Bb
Jinyuan No.1
1 382.9±13.2
Jiti No.5
1 418.1±12.5
Jilin No.5
1 506.7±14.3
Mean
1 435.9±63.8Cc
Capital letters mean extremely significant difference at 0.01 level, and small letters mean significant difference at 0.05 level.
http: //publish.neau.edu.cn
·16·
Journal of Northeast Agricultural University (English Edition)
Vol. 19 No. 3 2012
difference at the flowering stage was the biggest, the Changes of specific leaf weight in leaves of
value of high yield varieties was 23.3% higher than that
soybean with different yield levels at different
of low yield varieties. The difference at the seedling stage
growth stages
was smaller; the specific leaf weight of high yield varie-
From Fig. 1, we can see that the specific leaf weights
ties was 5.9% higher than that of low yield varieties.
of soybean varieties with different yield levels at different growth stages showed different changes,
Changes of chlorophyll content in leaves of
appearing a trend of first declining and then increasing
soybean with different yield levels at different
from seedling stage to maturity stage. The minimum
growth stages
value and maximum value appeared at the flowering
Fig. 2 showed that the chlorophyll content in the
stage and seed filling stage, respectively.
leaves of high yield varieties was higher than that in
Specific leaf weight (mg • dm-2)
the middle yield and low yield varieties. At the seed 700 650 600
550 500 450 400
of high yield varieties was 14.5% and 20.2% higher
V4
R2
than that in the middle yield and low yield varieties, respectively. At the maturity stage, the chlorophyll content in the leaves of high yield varieties was 10.6% and 26.8% higher than that in the middle yield and low
350 300
filling stage, the chlorophyll content in the leaves
Low yield cultivars Middle yield cultivars High yield cultivars
yield varieties, respectively. At the late growth stage, R4
R6
R7
Stage of growth
Fig. 1 Changes of specific leaf weight in leaves of soybean at different growth stages
the difference in chlorophyll content between the leaves of high yield and low yield varieties gradually became bigger. The chlorophyll contents in high yield varieties stayed at higher levels, indicating the slow down of aging, which laid the foundation for the
The specific leaf weights of varieties with higher
enhancement of photosynthesis.
growth stage. Among them, the biggest difference in specific leaf weight between high yield and middle yield varieties appeared at the seed filling stage, the value of high yield varieties was 5.7% higher than that of middle yield varieties. The difference at the maturity stage was the smallest, and the specific leaf weight of high yield varieties was 1.1% higher than that of middle yield varieties. The biggest difference in
Chlorophyll content (mg • dm-2)
yields were higher than those with lower yields at each 8 7 6 5
Low yield cultivars Middle yield cultivars High yield cultivars
4 3 2
V4
specific leaf weight between middle yield and low yield varieties appeared at the flowering stage, and the value of middle yield varieties was 3.9% higher than
R2
R4
R6
R7
Stage of growth
Fig. 2 Changes of chlorophyll content in leaves of soybean at different growth stages
that of low yield varieties. The difference at the seed filling stage was the smallest; the specific leaf weight
Changes of net photosynthetic rate in leaves
of middle yield varieties was only 0.1% higher than
of soybean with different yield levels at diffe-
that of low yield varieties. Comparing the specific leaf
rent growth stages
weights between high yield and low yield varieties, the
The net photosynthetic rates in leaves of soybean
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Li Da-yong et al. Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
varieties with three different yield levels were the
specific leaf weight, but did not reach significant level.
highest in high yield varieties, followed by middle yield varieties, and the lowest in low yield varieties at each growth stage (Fig. 3). During the whole growth stage, the net photosynthetic rates for each
Table 2 Relationships between soybean yield and specific leaf weight, chlorophyll content as well as net photosynthetic rate in soybean leaves at different growth stages
individual yield level variety slowly increased from the seedling stage, reached the peak values at the pod
Item
bearing stage, then declined, and finally reached the
Specific leaf
minimum values at the maturity stage. At the seedling,
weight
flowering, pod bearing, seed filling and maturity
Chlorophyll
stages, the net photosynthetic rates of high yield varieties were respectively 18.6%, 22.0%, 32.0%, 18.9% and 57.3% higher than those of low yield varieties, the difference was significant (P<0.05). At the seed filling and maturity stages, the net photosynthetic
content Net photosynthetic rate
V4
R2
R4
R6
R7
0.3008
0.6528*
0.2322
0.1556
0.8390**
0.2530
0.6383*
0.5733
0.5690
0.8602**
0.6187
0.7725
0.8683**
0.6694*
0.8573**
* and ** mean significant differences at 0.05 and 0.01 levels, respectively.
rates of high yield varieties were respectively 12.4% and 32.8% higher than those of middle yield varieties, the
At the flowering and maturity stages, the yield had
difference was significant (P<0.05). The enhancement
significantly positive correlations with the chlorophyll
of net photosynthetic rate in high yield varieties de-
content. Especially in maturity stage, the positive
monstrated their better substance synthesis capacity,
correlation was extremely significant (r=0.8602**). At
which laid the foundation for yield increase.
seedling, pod bearing and seed filling stages, the positive correlations between yield and chlorophyll con-
Pn (µmol • m-2• s-1)
35
tent were not significant (r=0.2530, 0.5733 and 0.5690).
30 25 20 15 10 5 0
There were significantly or extremely significantly
Low yield cultivars Middle yield cultivars High yield cultivars V4
R2
R4
positive correlations between soybean yield and net
photosynthetic rate at the flowering, pod bearing, seed
R6
R7
Stage of growth
filling and maturity stages (r=0.7725**, 0.8683**, 0.6694* and 0.8573**). At the seedling stage, the positive correlations between yield and net photosynthetic rate did not reach significant level (r=0.6187).
Fig. 3 Changes of net photosynthetic rate in soybean leaves at different growth stages
Discussion
Relationships between soybean yield and
Chlorophyll is the basic substance for leaves to absorb,
specific leaf weight, chlorophyll content as well
transfer and convert light energy. Hence, chlorophyll
as net photosynthetic rate in soybean leaves
content is closely related to the leaf photosynthetic rate
As can be seen from Table 2, the yield had signi-
(Zhang et al., 1986). The results in the present study
ficantly and extremely significantly positive correla-
demonstrated the chlorophyll content in the leaves of
tions with the specific leaf weight in soybean leaves
high yield soybean varieties appeared an increasing
at the flowering and maturity stages (r=0.6528* and
trend as compared with that of low yield varieties. The
0.8390**). At seedling, pod bearing and seed filling
soybean yield had a significantly positive correlation
stages, the yield had positive correlations with the
with the chlorophyll content in the leaves at the http: //publish.neau.edu.cn
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Journal of Northeast Agricultural University (English Edition)
Vol. 19 No. 3 2012
flowering and maturity stages, indicating that the
correlation was significant. The research results
increasing of chlorophyll content in the leaves of high
of Singh et al. (1993) demonstrated that yield was
yield varieties laid the foundation for the enhancement
positively correlated with the net photosynthetic
of photosynthetic rate and yield increase.
rate at flowering and filling stages. Wells et al.
Specific leaf weight is an important index of
(1982) considered soybean seed yield had a positive
leaf morphology and physiological traits. Owing to
correlation with apparent canopy photosynthesis curve
the simple and exact determination method, it is com-
at pod bearing and physiological maturity stages.
monly used for the comparative determination among
Du et al. (1999) pointed out that soybean yield was
varieties or strains (Gan et al., 1998). Specific leaf
positively correlated with photosynthetic rate at R 4
weight is also an index of source strength, which
stage. Zhou et al. (1990) also considered soybean seed
has close relationship to sink strength. The higher
yield had a significantly positive correlation with the
specific leaf weight and its longer duration are the
leaf photosynthetic rate at pod bearing and seed filling
performances of higher source strength. McClendon
stages (r=0.88**). Xu and Shen (1992) considered
(1962) and Orgren (1977) demonstrated that soybean
the negative correlation between yield and leaf
specific leaf weight was closely related to photo-
photosynthetic was a false appearance. Xu (1999) also
synthetic rate.
pointed out 95% of the plant dry matter came from
The present study showed that the specific leaf
assimilated CO2 by photosynthesis. This basic fact
weight in leaves of high yield soybean varieties was
determined the positive correlation between crop yield
the highest, followed by middle varieties, the low
and leaf photosynthetic rate, neither no correlation
yield varieties were the lowest. The soybean yield had
nor negative correlation. The positive correlations
significantly positive correlations with the specific leaf
were not a few exceptions but regular performance.
weight at the flowering and maturity stages, indicating
This internal positive correlation might be covered by
that the increasing of specific leaf weight in the leaves
the complex changes of other factors, for example,
of high yield varieties also laid the foundation for the
the yield of species with high leaf photosynthetic
enhancement of photosynthetic rate and yield increase.
rate might be lower than that of species with low
Zhang et al. (1986) pointed out that the yield was
leaf photosynthetic rate but large leaf area and long
positively correlated with the mean photosynthetic rate
photosynthesis functional period because of its small
at the main growth stage for each soybean variety, the
leaf area and short photosynthesis functional period.
correlation coefficient r was 0.8592, this trend could
The results in the present study indicated that
be maintained in different years. Evans and Rawson
there were significantly or extremely significantly
(1970) considered there was no stable correlation
positive correlations between soybean yield and net
between leaf photosynthetic rate of crops and
photosynthetic rate at the flowering, pod bearing,
productivity. Dong et al. (1979) studied eight soybean
seed filling and maturity stages. At the seedling
varieties and pointed out that mean net photosynthetic
stage, the positive correlation between yield and net
rate was obviously correlated with neither biological
photosynthetic rate did not reach significant level
yield nor economic yield.
(r=0.6187). The results were basically in accordance
Leaf photosynthesis is a dynamic process, which
with those of Zhang et al. (1986) and Xu et al (1999).
changes along with the growth stages (Patterson and Hoss, 1980). The study of Chu et al. (1988) indicated yield was positively correlated with net assimilation
Conclusions
rate at the early and middle growth stages, while
The specific leaf weight, chlorophyll content and net
negatively correlated at the late growth stage, no
photosynthetic rate of high yield soybean varieties
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Li Da-yong et al. Comparison of Net Photosynthetic Rate in Leaves of Soybean with Different Yield Levels
were higher than those of low yield varieties. The yield of soybean had significantly positive correlations with the specific leaf weight, chlorophyll content and net photosynthetic rate. Among them, the correlation between yield and net photosynthetic rate was closer
London. pp. 721-733. Patterson T G, Hoss D N. 1980. Enzymatic changes during the senescence of field-grown wheat. Crop Science, 20: 19-23. Pearce R B, Carlson G E, Barn S D K. 1969. Specific leaf weight and photosynthesis in alfalfas. Crop Science, 9: 423-426.
than those between yield and specific leaf weight as
Singh S P, Lal K B, Ram R S, et al. 1993. Photosynthetic efficiency
well as chlorophyll content. With the improvement
and productivity of pigeonpea. Indian Journal of Pulses Research, 6:
of modern technology, the net photosynthetic rate
212-214.
could be measured quickly and exactly. Hence, net photosynthetic rate could be used as an effective index in the selection of high yield soybean, which could reduce breeding blindness.
Sun H. 2005. Jilin Soybean. Jilin Science and Technology Press, Changchun. pp. 124-125. Wang J A, Ning H L, Luo Q X, et al. 2004. The content of chlorophyll, the activity of RUBP and Hill and their correlations with yield . Journal of Northeast Agricultural University, 35(2): 129-134.
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