The Photosynthetic Characteristics Of Rubisco Activase Transgenic Rice Under Salt Stress

Salinity is one of the most important abiotic factors which limit crop productivity. Photosynthesis has a close relationship with the crop productivity. It is very important to illuminate the mechanism of how salt stress affects photosynthesis. A wild type rice plant (wt)、 RCAL and RCAs over expression transgenic rice plant (ss,bs) and a RCA antisense transgenic rice plant (mt) were used for studying the effects of salinity on the gas exchange parameters, chlorophyll fluorescence parameters、Rubisco activity and the content of RCAL and RCAs. Under salt stress, within the four types of rice plant, stomatal conductance (gs) decreased with the increase of the concentration of NaCl, but the intercellular CO2concentration (Ci) did not change significantly. The photosynthetic rate did not change significantly at100mM NaCl but decreased rapidly at200mM NaCl, indicating non-stomatal limitation was responsible for the photosynthetic suppression. The change of chlorophyll fluorescence parameters and P700parameters in the four types of rice plant were not very consistent and did not change significantly, indicating the salt stress did not affect the PS Ⅰ,PS Ⅱ and electron transport to a damaging degree. The effects of salt stress on post-illumination transient increase in chlorophyll and dark re-redunction of P700+after far-red light showed that the salinity did not increase the CEF1. By analyzing the CO2response curve, it was indicated that Rubisco activity was depressed, and the Rubisco activity in vitro experiment showed that the initial activity decreased but the total activity did not change. So the initial activity of Rubisco is a non-stomatal limitation to the suppression of photosynthesis. In conclusion, RCA gene transfer rice did not enhance the tolerance to salt stress.