Biomass, Gas Exchange and Chlorophyll Fluorescence in Wheat Seedlings under Salt and Alkali Stress

Gas exchange and chlorophyll fluorescence are two very important physiological processes affecting plant growth.The experiment was simulated by salt and alkali stresses.Shoots biomass, gas exchange and chlorophyll fluorescence parameters of wheat were measured after 9 d of treatments.The shoot biomass and gas exchange indices decreased significantly with the increasing salt concentration, and more for alkaline stress at the same concentration, except for Ci concentration.Compared to saline and alkaline stresses with controls, the Fv/Fm was not changed under both stresses, but qp increased; PS II maximum efficiency (Fv′/Fm′) was not affected by salinity, but decreased under alkalinity; PS II efficiency (φPS II) and electron transport rates (ETR) only increased significantly at lower concentration (40 mmol/L) under salt stress, and didn't change at other concentration, but ETR decreased at higher concentration (120 mmol/L) under alkali stress; qN did not change at salinity, but enhanced significantly at 120 mmol/L concentration under alkalinity.Therefore, photosynthetic performance response of wheat seedling to salt and alkali stresses was very different.PN was affected by both stomatal and non-stomatal factors under salt and alkali stresses.Photo-protection caused by photo-inhibition happened at the highest level of alkali stress, depending on high pH and salinity.The wheat variety Jimai 3 in present stud y has tolerance to moderate salinity and alkalinity.