Study On Physiological Responding To High Temperature Stress In Two Moss Species

In order to study the effects on physiological response of Grimmia pilifera and Racomitrium canescens, which were treated by high temperature(60?) or sub-high temperature(40?) For different time respectively. Net photosynthesis rate, gas exchange, chlorophyll fluorescence and the response of active oxygen scavenging enzyme system to high temperature were detected as the main indexes. After analyzing the two mosses recovered from the stress, the possible response mechanism of high temperature on physiological and activities of light system were discussed. The main results are as Follows:First, under the stress of different high temperatures, net photosynthesis rate of the two species of mosses firstly increased and then decreased. With the increase of temperature and treatment time, light saturation point(LSP),max Pn(Pm), apparent quantum yield(AQY) and carboxylation efficiency(CE) of two mosses were decreased, meanwhile, light compensation point(LCP) was increased. The results showed that the capabilities of two mosses to use weak light and high intensive light were lower than the control. The activity of Rubisco and the capability of using lower concentration CO2 were lower too. Decreased chlorophyll content under high temperature stress may be one main cause resulting in the reducing of Pn.Second, the intrinsic photochemical efficiency(Fv/Fm), quantum yield of PS ?( ?PS?), the efficiency of excitation energy captured by open PS reaction center?(Fv'/Fm')of plants were all decreased, initial fluorescence was increased, showed that react center was protected by decreasing light capture and efficiency of electron transformation through PS?.Third, under different high temperature stresses, active oxygen scavenging enzyme system, proline content, soluble protein, soluble sugar and MDA of the two species of mosses were all changed undulate with the increase of temperature and treatment time, showing that through adjusting the active oxygen scavenging enzyme system and the accumulation of osmotic regulation substances ensured the physiological and biochemical responses of the cell membrane to proceed normally.Fourth, the two mosses were transmitted into the condition of the control after relieving the stress, net photosynthetic rate and maximal photochemical efficiency of PS?could recover within 5 days. G. pilifera and R. canescens can endure high temperature, and short-term high temperature damage to them is reversible.