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| DOI：10.13522/j.cnki.ggps.2020173 |
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| Reduction in Photosynthesis of Cotton Seedling under Water and Salinity Stresses is Induced by both Stomatal and Non-stomatal Limitations |
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Mounkaila Hamani Abdoul KADER, SHEN Xiaojun, CHEN Jinsai, WANG Guangshuai, GAO Yang
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1.Farmland Irrigation Research Institute, Chinese Academy of Agricultural Sciences, Xinxiang 453002, China；2.Graduate School of Chinese Academy of Agricultural Sciences, Beijing 100081, China
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| Abstract: |
| 【Background】 Drought and salinity are two common abiotic stresses facing agricultural production in arid and semi-arid regions and salt-affected regions. An elevated soil salt content is lethal to plant growth, which reduce plant productivity of irrigated agriculture worldwide by about 20%. NaCl-induced soil salinity has attracted increased concern for its impact on non-halophytic plants as it alters plant metabolism due to its ion toxicity and the increased osmotic potential. Cotton, as the largest fiber source for textile, is a crop with moderate salt-tolerance, but salinity exceeding a certain level could still impede its growth and development dramatically, especially for salinity occurring at seedling stage, by inhibiting the photosynthesis. Reduction in photosynthesis is the most important response of cotton to water and salinity stresses, but the mechanisms underlying the relative significance of stomatal restriction and non-stomatal restriction in this reduction remains obscure despite its importance in sustaining cotton production.【Objective】This paper aims to experimentally investigate the response of photosynthesis of cotton seedlings to water and salinity stresses in both isolation and combination. 【Method】Pot experiments were conducted in a phytotron to examine the effects of different water and salinity stresses on stomatal characteristics, pigment content, photosynthetic rate and chlorophyll fluorescence of cotton seedling. We compared four treatments: water stress only (T2), salinity stress only (T3), combining water and salinity stress (T4), with the absence of any stresses taken as the control (CK).【Result】Compared to CK, T1 did not reduce the length and width of the stomata at significant level, but reduced the stomatal density markedly. In contrast, T3 and T4 reduced the length, width and density of the stomata at significant level despite the difference between T3 and T4 being insignificant. In addition to reducing photosynthetic rate, all treatments also reduced the contents of chlorophyll a and b, as well as the carotenoid in the leaves at significant level. The difference in carotenoid content between T3 and T4 was significant. The photosynthesis in CK was reduced mainly by biochemical characteristics; the average stomatal and mesophyll limitations in photosynthesis under T2—T4 was 0.38 and 0.35 respectively, indicating that the decline in photosynthesis was primarily due to the stomatal and mesophyll limitation. When photosynthesis was inhibited, the cotton seedlings dissipated excessive energy via heat dissipation.【Conclusion】Under water and salinity stresses, the photosynthesis of cotton seedling was inhibited by stomatal and mesophyll limitation. |
| Key words: cotton; salinity stress; water stress; photosynthesis rate; stomatal limitation; non-stomatal limitation |
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