光强对苗期大豆叶片水力导度及叶脉性状的影响

doi:10.3864/j.issn.0578-1752.2023.22.005

摘要/Abstract

摘要：

【目的】探究光强对苗期大豆叶片水力导度、光合特性和叶水势的影响，分析叶脉性状对不同生长光强的适应机制，为提高大豆光能利用提供理论支撑。【方法】选用强耐荫型的大豆品种南豆12和弱耐荫型的大豆品种桂夏7为试验材料，在人工气候室进行盆栽试验，设置高光强（（424.47±12.32）µmol·m^-2·s^-1，HL）、中光强（（162.52±20.31）µmol·m^-2·s^-1，ML）和低光强（（93.93±9.87）µmol·m^-2·s^-1，LL）处理。在处理20 d后研究不同生长光强对苗期大豆叶片水力导度、光合参数、叶片水势及叶脉性状的影响。【结果】相对于高光强处理，低光强处理下南豆12和桂夏7的叶片水力导度显著降低，南豆12的叶片水力导度在3个处理下均显著高于桂夏7。与高光强处理相比，在中、低光强处理下南豆12的叶片水力导度分别降低7.56%和21.24%，气孔导度分别降低43.96%和58.89%，净光合速率分别降低29.44%和46.49%。同样，桂夏7的叶片水力导度分别降低42.16%和23.71%，气孔导度分别降低54.55%和45.79%，净光合速率分别降低37.03%和42.06%。南豆12和桂夏7的叶片水势在处理间均无显著差异。大豆的叶片水力导度与气孔导度在3个光强处理下均达到极显著正相关（P<0.01），随着光强的降低，叶片水力导度与净光合速率呈显著正相关（P<0.05），与气孔导度呈极显著正相关（P<0.01）。对于叶脉结构，与高光强相比，中、低光强处理下两个大豆品种的小叶脉密度以及主叶脉和小叶脉的木质部导管面积均显著降低，且南豆12的小叶脉密度和主叶脉木质部导管面积在中、低光强处理下均显著高于桂夏7。南豆12的主叶脉密度在处理间无显著变化，桂夏7的主叶脉密度在中、低光强处理下较高光强显著降低11.4%和15.0%。光强降低显著增长了叶脉到气孔的距离。南豆12在中、低光强处理下叶脉到气孔的距离较高光强增长21.33%和60.01%，桂夏7叶脉到气孔的距离增长31.50%和53.59%。相关性分析表明，大豆叶片水力导度与小叶脉密度、主叶脉和小叶脉的木质部导管面积呈显著正相关（P<0.05），与叶脉到气孔的距离呈极显著负相关（P<0.01）。【结论】光强会通过调控大豆叶脉结构影响叶片水力导度，弱光降低大豆叶片水力导度，但叶片水力导度和气孔导度保持协调，维持叶片水分供需平衡。弱光下具有较高的叶脉密度能够缩短水分运输的距离，保证较好的叶片水分供应能力，从而有利于CO₂的扩散和光合作用，这是耐荫型大豆适应弱光环境的又一策略。

关键词: 大豆, 叶片水力导度, 气孔导度, 光强, 叶脉

Abstract:

【Objective】The objective of this study is to explore the effects of light intensity on leaf hydraulic conductivity, photosynthetic traits, and water potential in soybean seedlings, analyze the adaptive mechanisms of leaf vein traits in response to varying light intensities, and to provide theoretical support for enhancing future light energy utilization in soybean.【Method】Two soybean varieties, Nandou 12 (shade-tolerant) and Guixia 7 (shade-sensitive), were cultivated and placed in growth chambers. The plants were exposed to varying light conditions, including high light intensity (HL) at (424.47±12.32) µmol·m^-²·s^-¹, medium light intensity (ML) at (162.52±20.31) µmol·m^-²·s^-¹, and low light intensity (LL) at (93.93±9.87) µmol·m^-²·s^-¹. After a 20-day treatment period, the impacts of different light intensities on hydraulic conductivity, photosynthetic parameters, leaf water potential, and leaf vein traits in the seedling leaves of soybean were examined.【Result】Compared with HL treatment, the leaf hydraulic conductivity of Nandou 12 and Guixia 7 under LL treatment was significantly decreased, and the leaf hydraulic conductivity of Nandou 12 under the three treatments was significantly higher than that of Guixia 7 under the three treatments. Compared with HL treatment, the leaf hydraulic conductivity of Nandu 12 under ML and LL treatments decreased by 7.56% and 21.24%, stomatal conductance decreased by 43.96% and 58.89%, and net photosynthetic rate decreased by 29.44% and 46.49%, respectively. Similarly, the leaf hydraulic conductivity of Guixia 7 under the ML and LL treatments decreased by 42.16% and 23.71%, stomatal conductance decreased by 54.55% and 45.79%, and net photosynthetic rate decreased by 37.03% and 42.06%, respectively. Additionally, no statistically significant differences were observed in the leaf water potential of both soybean varieties across the various treatments. Notably, leaf hydraulic conductivity and stomatal conductance of soybean exhibited a highly significant positive correlation (P<0.01) under the three light intensity treatments. As the light intensity decreased, a positive correlation was observed between leaf hydraulic conductivity and net photosynthetic rate (P<0.05) as well as stomatal conductance (P<0.01). Conversely, there was a noticeable decrease in the minor leaf vein density and the area of xylem conduits in major and minor veins under the ML and LL treatments for both soybean varieties. In the case of the minor leaf vein density and the area of xylem conduits in major veins, Nandou 12 exhibited significantly higher values than Guixia 7 under the ML and LL treatments. The major leaf vein density of Nandou 12 remained relatively stable across treatments, while that of Guixia 7 experienced a significant reduction of 11.4% and 15.0% under the ML and LL treatments compared to the HL treatment. Furthermore, a decrease in light intensity had a notable effect on increasing the distance between leaf veins and stomata. Specifically, under the ML and LL treatments, the distance from veins to stomata increased by 21.33% and 60.01% for Nandou 12 and by 31.50% and 53.59% for Guixia 7 in comparison to the HL treatment. The correlation analyses revealed significant positive correlations (P<0.05) between the hydraulic conductivity of soybean leaves and the density of minor leaf veins, the area of xylem conduits in major and minor veins. Conversely, a significant negative correlation (P<0.01) was observed between hydraulic conductivity and the distance from veins to stomata.【Conclusion】Light intensity exerts an influence on the leaf hydraulic conductivity by modulating the leaf vein structure of soybean. Under low light conditions, there is a reduction in leaf hydraulic conductivity in soybean; however, the coordination between leaf hydraulic conductivity and stomatal conductance is maintained to establish equilibrium between leaf water supply and demand as light intensity diminishes. The presence of a higher vein density under low light serves to abbreviate the distance required for water transport, thereby enhancing leaf water supply capacity. Consequently, this facilitates CO₂ diffusion and photosynthesis, representing an additional strategy employed by shade-tolerant soybean to acclimate to low-light environments.

Key words: soybean, leaf hydraulic conductivity, stomatal conductance, light intensity, leaf vein

高静, 陈吉玉, 谭先明, 吴雨珊, 杨文钰, 杨峰. 光强对苗期大豆叶片水力导度及叶脉性状的影响[J]. 中国农业科学, 2023, 56(22): 4417-4427.

GAO Jing, CHEN JiYu, TAN XianMing, WU YuShan, YANG WenYu, YANG Feng. Effect of Light Intensity on Leaf Hydraulic Conductivity and Vein Traits of Soybean at Seedling Stage[J]. Scientia Agricultura Sinica, 2023, 56(22): 4417-4427.

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处理 Treatment	光照强度 <BOLD>L</BOLD>ight intensity (µmol·m^-2·s^-1)	红光/远红光 Red/Far-red
高光强HL	424.47±12.32	9.50±0.3
中光强ML	162.52±20.31	9.35±0.4
低光强LL	93.93±9.87	9.61±0.2

处理 Treatment	品种 Variety	气孔导度G_s (mol H₂O·m^-2·s^-1)	净光合速率P_n (μmol CO₂·m^-2·s^-1)	蒸腾速率E (mmol H₂O·m^-2·s^-1)	胞间二氧化碳浓度C_i (μmol CO₂·mol^-1)	叶片水力导度/气孔导度 K_leaf/G_s (-Mpa)
高光强HL	ND12	0.91±0.10a	17.83±6.41a	7.92±0.32a	400.29±6.41ab	0.009±0.001c
高光强HL	GX7	0.56±0.13b	18.71±12.29a	6.57±0.79ab	388.35±12.29bc	0.011±0.003bc
中光强ML	ND12	0.51±0.18bc	12.53±12.30b	6.57±1.28ab	411.77±12.30a	0.017±0.006ab
中光强ML	GX7	0.25±0.07d	11.78±17.53bc	4.53±0.75c	373.83±17.53c	0.014±0.003abc
低光强LL	ND12	0.38±0.06bcd	9.54±5.71c	5.73±0.52bc	412.80±5.71a	0.018±0.003ab
低光强LL	GX7	0.30±0.11cd	10.84±7.87bc	4.99±1.13bc	379.86±7.87bc	0.018±0.007a

处理 Treatment	品种 Variety	主叶脉密度 VLA_major (cm·cm^-2)	小叶脉密度 VLA_minor (cm·cm^-2)	气孔密度 Stomatal density (n/mm²)	叶脉到气孔的距离D_m (μm)	主叶脉木质部导管面积 X_major(μm²)	小叶脉木质部导管面积 X_minor(μm²)
高光强HL	ND12	1.49±0.05a	52.06±5.79a	267.73±24.23a	112.48±22.15c	1102.35±97.21a	34.21±4.31a
高光强HL	GX7	1.40±0.13a	40.58±5.21a	226.25±25.49b	127.98±16.13c	992.44±57.21ab	37.22±6.99a
中光强ML	ND12	1.42±0.02ab	34.07±0.93b	165.21±32.99c	136.48±13.48c	900.29±47.39b	29.38±3.02b
中光强ML	GX7	1.24±0.11b	29.86±3.15c	150.65±7.36cd	168.30±16.75b	800.29±66.96cd	27.63±4.11b
低光强LL	ND12	1.46±0.14a	29.10±1.81c	136.25±12.16cd	179.98±15.71ab	746.31±32.05c	24.94±2.59bc
低光强LL	GX7	1.19±0.17b	25.53±2.67d	112.80±6.64e	196.56±20.98a	648.33±84.21d	21.29±2.06c

参数 Parameter	叶片水力导度 K_leaf	小叶脉密度VLA_minor	叶脉到气孔的距离D_m	主叶脉木质部导管面积X_major	小叶脉木质部导管面积X_minor	气孔密度 Stomatal density
小叶脉密度VLA_minor	0.73*	1
叶脉到气孔的距离D_m	-0.80**	-0.91***	1
主叶脉木质部导管面积X_major	0.68*	0.65*	-0.68*	1
小叶脉木质部导管面积X_minor	0.69*	0.73*	-0.75*	0.66*	1
气孔密度Stomatal density	0.62*	0.97***	-0.93***	0.66*	0.74*	1