Effects of 1-butanol, neomycin and calcium on the photosynthetic characteristics of pepc transgenic rice

Abstract

The effects of 1-butanol, neomycin and calcium on the photosynthesis of pepc transgenic rice were studied with over-expressed pepc transgenic rice (PC) of the 8th generation as study materials and with non-transgenic wild type (WT) rice and maize, a typical C₄ plant, as control. The results show that, 0.04% 1-butanol and 0.05 mmol L^-1 Ca<sup<2+ has a significant effect on the net photosynthetic rate (P_n) of the three tested materials. Furthermore, when compared with the WT, PC under different treatments maintained a relatively high P_n. The stepwise multiple linear regression analysis showed that, PC maintained its relative high P_n through the increase of stomatal conductance. It was proved by the scanning electron microscope (SEM) that, when compared with the WT, the stomatal density of PC leaves increased while the stomatal aperture also increased under the 1-butanol treatment. The phosphoenolpyruvate carboxylase (PEPC) activity of PC and maize leaves were significantly inhibited after the 1-butanol treatment alone, while they had no significant effects after the neomycin treatment alone. However, the combined treatment with 1-butanol and neomycin evidently promoted the PEPC activity of PC and WT. Moreover, exogenous calcium significantly promoted the PEPC activity of the three materials. It is clear that, the exogenous regulation on PC is different from both C₄ and C₃ plants. PC might regulate stomatal aperture primarily by the calcium-mediated phospholipase D (PLD) pathway, which also increases the leaf stomatal density, thus, raising the stomatal conductance and showing a relatively high P_n.

Key words: Pepc transgenic rice, 1-butanol, neomycin, photosynthesis, stomatal conductance.