PHOTOSYNTHESIS, STOMATAL CONDUCTANCE, ENDOGENOUS HORMONES AND ORGANIC ACID SYNERGISTIC REGULATION IN LEAVES OF RICE (ORYZA SATIVA L.) UNDER ELEVATED CO2
X.F. QI, X.H. WANG, Q. WANG, M. LI, L.J. MA, Y.Y. LI, X.M. LI, L.L. WANG
Abstract
To study the photosynthesis, stomatal conductance, endogenous hormones and organic acid regulation in leaves of rice seedlings under elevated CO2, rice were exposed to different CO2 concentrations (40020 mol mol -1 , AA; 60020 mol mol -1 , LEC; 80020 mol mol -1 , HEC) for 7 days. The results showed that: The elevated CO2 increased IAA (Indole-3-acetic acid, IAA), ZT (Zeatin, ZT) and GA3 (Gibberellins A3, GA3) contents significantly (p<0.05), which regulated the increasing Pn (Light-saturated net photosynthesis rate, Pn) and Fv/Fm (Maximum quantum yield of PSII photochemistry, Fv/Fm); Gs (Stomatal conductance, Gs) and Tr (Transpiration rate, Tr) were all decreased significantly (p<0.05), while ABA (Abscisic acid, ABA) content also decreased, but JA (Jasmonic acid, JA) content increased significantly (p<0.05) under EC. Perhaps, the movements of stoma were connected with JA in some degree, but not ABA; IAA/ABA, GA3/ABA and ZT/ABA were all increased under EC, indicating the promoting effects of photosynthesis. JA/GA3 decreased under LEC, but increased under HEC, which regulated the elevated Pn under LEC, and severe closure of stomata under HEC. The contents of oxalic acid, tartaric acid, acetic acid, malic acid, lactic acid, fumaric acid and succinic acid significantly decreased (P<0.05) in leaves, but contents of citric acid showed no significant difference with AA under HEC, indicating that the TCA cycle rate slowed down.