基于FvCB模型分析盐分胁迫对棉花叶片光合作用的影响

为深入理解叶片光合特性对盐胁迫的响应机理,以棉花为试验材料,设置5个盐分(NaCl)浓度处理:0(CK)、50、100、150和200 mmol·L^-1,利用FvCB模型分析盐胁迫对棉花幼苗叶片光合特性的影响。结果表明:与CK相比,50和100 mmol·L^-1盐分处理增加了棉花叶片的最大羧化速率(V_{c max})和最大电子传递速率(J_max),但150和200 mmol·L^-1盐分处理显著降低了V_{c max}和J_max。叶片净光合速率(P_n)、叶肉导度(g_m)和暗呼吸速率(R_d)随盐分浓度升高而下降;与CK相比,50和100 mmol·L^-1盐分处理对g_m无显著影响,但P_n和R_d显著降低。150和200 mmol·L^-1盐分处理明显降低了P_n、g_m和R_d,且与0、50和100 mmol·L^-1盐分处理间存在显著差异;利用FvCB模型模拟了不同盐分胁迫下叶片净光合速率。与不考虑g_m的模拟结果相比,考虑g_m提高模拟值和实测值间的决定系数,并降低了平均绝对误差。棉花幼苗耐盐阈值为100～150 mmol·L^-1,随盐分浓度的增加,光合限制因素由叶肉因素转变为光合机构受损;引入g_m可以提高FvCB模型的模拟精度。

Examining effects of salt stress on leaf photosynthesis of cotton based on the FvCB model

To understand the responsive mechanism of leaf photosynthesis of cotton to salinity stress, we investigated the effects of salt stress on leaf photosynthetic characteristics of cotton seedlings with the FvCB model under five levels of salt concentration, i.e., 0 (CK), 50, 100, 150 and 200 mmol·L^-1. Results showed that, compared with CK, the salt concentrations of 50 and 100 mmol·L^-1 increased the maximum carboxylation rate (V_{c max}) and the maximum electron transport rate (J_max), while the salt concentrations of 150 and 200 mmol·L^-1 significantly decreased V_{c max} and J_max. The net photosynthetic rate (P_n), mesophyll conductance (g_m) and dark respiration rate (R_d) gradually decreased with the increases of salt concentration. Compared with CK, the salt concentrations of 50 and 100 mmol·L^-1 did not affect g_m, but significantly decreased P_n and R_d. The salt concentrations of 150 and 200 mmol·L^-1 significantly decreased P_n, g_m and R_d, which were significantly different from the salt concentrations of 0, 50 and 100 mmol·L^-1. P_n of cotton seedlings under different salt concentrations was simulated by the FvCB model. Compared with the results from the FvCB model without considering g_m, the FvCB model with g_m improved the determination coefficient between the simulated and measured values and decreased the mean absolute error. The salinity threshold of cotton seedlings ranged between 100 and 150 mmol·L^-1. With the increases of salt concentration, the limiting factor of leaf photosynthesis changed from mesophyll conductance to impaired components of photosynthetic apparatus. The FvCB model combined g_m could improve the accuracy of photosynthesis simulation.