Response of photosynthesis and chlorophyll fluorescence to drought stress in two maize cultivars

Abstract

This study investigated the changes of leaf photosynthetic characteristic and chlorophyll fluorescence parameter responding to drought stress (DS) in two species of maize at elongating stage. The results of net photosynthesis rate (Pn) and light intensity response curve indicated that Pn reduced with enhanced light intensity. Photoinhibition in varying degrees appeared in different genotype varieties, and DS intensified the extent of photoinhibition. Results showed that for DS at elongating stage, Pn of the cultivar JD28 was insensitive to highlight. Pmax and Rd decreased, and physiological activity reduced obviously. Compared with JD28, JD261 decreased more. Moreover, DS resulted in decreased light compensation point (LCP) and light saturation point (LSP). And it caused highlight utilization ratio reduced but weak light use efficiency increased. JD28 had higher light use efficiency. Diurnal variation curve of Fv/Fm changed greatly in DS and there was no significant difference between the two species. DS treatments decreased photochemical quenching (qP), PhiPS2 and Fv’/Fm’, while it increased non-photochemical quenching (NPQ). The reduction of PhiPS2 was caused by the decrease of qP and Fv’/Fm’. DS treatments weakened maize leaves’ capability of assimilation, transformation and light energy utilization. JD28 could use more light than JD261 in photosynthesis. While JD261’s light use efficiency was lower, the less light used for photosynthesis and the excessive photon flux energy was dissipated in form of heat. Key words: Elongating stage, maize, drought-tolerance, photosynthesis.