Damage characteristics of photosynthetic system of two typical ephemeral plants in Mosuowan area caused by temperature and light postprint

Abstract: To explore the photosynthetic system adaptation mechanism of two dominant ephemeral plants, including Malcolmia scorpioides and Arnebia decumbens, to light and temperature, this study measured the chlorophyll fluorescence parameters and discussed its light damage and the change of photosynthetic activity under different temperatures (25-60 ℃) and constant room temperature and high temperature and different illumination (80-400 μmol·m-2·s-1). The results were as follows: (1) The photosynthetic efficiency and electron transfer rate increased first and then decreased with the increase of temperature, reaching the highest value at 40 ℃, and then rapidly decreased, and the quantum yield of non-regulated energy dissipation in PS Ⅱ [Y(NO)] and PS I receptor side heat dissipation efficiency [Y(NA)] increased, and the photosynthetic system was damaged due to the accumulation of excitation pressure at the receptor terminal. (2) Under the light range of 80-400 μmol·m-2·s-1 and room temperature, the photosynthetic efficiency increased with the enhancement of light intensity; Under high temperature, the combined stress of light and high temperature on plants descended the photosynthetic activity of plants and the quantum yield of regulatory energy dissipation in PS II [Y(NPQ)], and when the light intensity reaches 320 μmol·m-2·s-1, the ring electron transport flow disappeared. In conclusion, light and temperature within a certain range can improve the photosynthetic activity, activate heat dissipation and ring electron transport flow and reduced photoinhibition. However, with the increase of temperature and light intensity at high temperature, the adaptation ability of the two ephemeral plants decrease and the photoprotective mechanism disappeared. The main reason is the failure of regulatory heat dissipation and the accumulation of PS I receptor side excitation pressure.