盐胁迫对银叶树幼苗光合特性与叶绿素荧光参数的影响

Effects of NaCl stress on the photosynthesis and cholorophyll fluorescence of Heritiera littoralis seedlings

以1年生的银叶树幼苗为试材,采用NaCl配制所需盐水浓度,定期定量浇灌盐水,设置土壤含盐量分别为0%、1.2%、1.5%和1.8%,在施盐60 d后,对银叶树叶片叶绿素含量、光合参数以及叶绿素荧光特性进行了观测,研究不同盐胁迫处理对银叶树光合生理的影响,探究其耐盐能力。结果表明,银叶树幼苗叶片Chl a、Chl b含量与Chl a/Chl b随着盐胁迫的增加呈现出先升后降的趋势。盐胁迫降低了银叶树净光合速率(P n)、蒸腾速率(T r)、气孔导度(G s);叶绿素荧光与光合作用效率密切相关,盐胁迫降低了银叶树幼苗叶片实际光量子效率与表观光合电子传递速率,导致银叶树光化学效率与表观净光合速率降低。轻度盐胁迫下净光合速率的下降主要是受气孔关闭的制约,随着盐胁迫的增加,非气孔因素成为银叶树净光合速率下降的主要原因。盐胁迫下银叶树启动光保护机制,以热耗散途径为主的PSⅡ调节性能量耗散,保护光合机构免受伤害。研究表明,银叶树作为半红树具有较强的耐盐性能。

Aiming to explore the photosynthetic physiology and NaCl tolerance of Heritiera littoralis seedlings under different NaCl stress environments.We created soil NaCl gradients of chlorophyll content,photosynthetic parameters and chlorophyll fluorescence were measured for one-year-old seedlings under a solt treatment with 0%,1.2%,1.5%and 1.8%NaCl for 60 d.The result showed that the chlorophyll content and the ratio of Chl a to Chl b displayed a hump-shaped pattern with NaCl stress increasing.NaCl stress decreased net photosynthetic rate(P n),transpiration rate(T r)and stomatal conductance(G s)in H.littoralis.Cholorophyll fluorescence and photosynthesis were highly related,and the decline in actual quantum efficiency and apparent photosynthetic electron transfer rate due to NaCl stress led to the decline in photochemical efficiency and apparent net photosynthetic rate.Under mild NaCl stress,the decrease in photosynthetic rate may result from constraint of stomatal closure,while with increasing NaCl stress,the decrease may result from non-stoma related factors.Photoprotective mechanism may be activated under NaCl stress,in which heat dissipation path was the main pathway and protect photosynthetic apparatus from damage.Together,this study suggests that H.littoralis as a semi-mangrove tree is relative tolerant to high NaCl stress.