摘要
摘要:探讨盐胁迫下紫花苜蓿幼苗叶片光合生理特性，可为改善紫花苜蓿生长，修复生态环境，推动牧草产业快速发展奠定基础。本研究以‘阿迪娜’为试验材料，设0 mmol·L^-1（CK）、40 mmol·L^-1、80 mmol·L^-1、120 mmol·L^-1和160 mmol·L^-1共5个NaCl水平，使用Li-6400XT光合仪测定不同盐胁迫下紫花苜蓿幼苗光响应-CO₂曲线，利用FvCB模型分析盐胁迫对紫花苜蓿幼苗光合特性的影响。结果表明：1）不同NaCl胁迫下叶片净光合速率（P_n）随NaCl浓度的增加而降低，与CK相比，4个NaCl胁迫下分别降低1.44%、3.85%、7.21%和7.90%，均达显著性水平（P < 0.05）；随光合有效辐射的增加均呈迅速上升趋势，CK的P_n增长速度显著高于其他处理。2）与CK相比，40 mmol·L^-1和80 mmol·L^-1 NaCl胁迫增加了紫花苜蓿幼苗叶片的最大羧化速率（V_cmax）和最大电子传递速率（J_max），但120 mmol·L^-1和160 mmol·L^-1NaCl胁迫显著降低了V_cmax和J_max。3）叶肉导度（g_m）和暗呼吸速率（R_d）随NaCl胁迫水平的增加呈降低趋势；与CK相比，40 mmol·L^-1和80 mmol·L^-1 NaCl胁迫的g_m变化不显著，但R_d显著降低。120 mmol·L^-1和160 mmol·L^-1 NaCl胁迫显著降低了g_m和R_d，且与CK、40 mmol·L^-1和80 mmol·L^-1 NaCl胁迫间呈显著性差异。4）验证FvCB模型中子模型估算植物叶片光合的精确度，发现FvCB模型对不同胁迫处理下P_n拟合时，引入g_m模型模拟精度高，平均绝对误差低。5）紫花苜蓿幼苗耐盐临界值为80~120 mmol·L^-1，随NaCl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。该研究可为我国西北地区盐碱地制定有效的调控措施以提高植物耐盐能力提供科学参考。
关键词:紫花苜蓿/
盐胁迫/
FvCB模型/
最大羧化速率/
最大电子传递速率
Abstract:Understanding the photosynthetic physiological characteristics of alfalfa seedlings under salt stress is important for improving alfalfa growth, restoring the ecological environment, and promoting the development of the foraging industry in China. Alfalfa variety 'Adrenalin' seedlings were treated with different concentrations of NaCl (0 mmol·L^-1, CK; 40 mmol·L^-1, T1; 80 mmol·L^-1, T2; 120 mmol·L^-1, T3; and 160 mmol·L^-1, T4), the light response curves were measured with Li-6400XT, and the effects of NaCl stress on photosynthetic characteristics were analyzed by using FvCB model. The results showed that the leaf net photosynthetic rate (P_n) decreased significantly with increasing NaCl concentration by 1.44% (T1), 7.21% (T2), 7.90% (T3), and 3.85% (T4), respectively, compared with that of CK. The P_n in all treatments showed a rapid upward trend as photosynthetic effective radiation increased, and the P_n growth rate in the normal treatment (CK) was significantly higher than that in the other treatments. Compared with those in the CK, the T1 and T2 treatments increased the alfalfa seedling leaf maximum carboxylation rate (V_cmax; by 3.59% in T1, and 13.88% in T2) and maximum electron transfer rate (J_max; by 11.24% in T1, and 17.47% in T2), but the T3 and T4 treatments reduced V_cmax and J_max. Leaf conductance (g_m) and dark respiration rate (R_d) decreased with increasing NaCl concentration. Compared with those in the CK, the T1 and T2 treatments did not affect g_m, but significantly reduced R_d. The T3 and T4 treatments significantly reduced g_m and R_d compared with CK, T1, and T2 treatments. The FvCB model fitting results of alfalfa P_n under different stress treatments verified that the FvCB sub-model accurately estimated plant leaf photosynthesis, and the results showed that introducing g_m into the model had a high simulation accuracy and low average absolute error. The critical salt tolerance value for alfalfa seedlings was 80–120 mmol·L^-1. As the NaCl concentration increased, the photosynthetic limiting factors changed from mesophyll factors to damaged photosynthetic organs. These results may help formulate effective control measures in Northwest China saline land to improve plant salt tolerance.
Key words:Alfalfa/
Salt stress/
FvCB model/
Maximum carboxylation rate/
Maximum electron transport rate



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