Photosynthetic characterization of a rolled leaf mutant of rice (Oryza sativa L.)
A new rolling leaf rice mutant was identified which showed an apparently straighter longitudinal shape normal transverse rolling characters at all developing stages. The chlorophyll contents per fresh weight of this mutant leaves were lower than those of wild-type. The electron transfer rate (ETR) and photochemical quenching (qP) were a little higher than those of wild-type. However, because of significant increase of non-photochemical quenching (NPQ), the maximal photosystem II (PSII) photochemistry (Fv/Fm) and the efficiency of excitation energy trapping by open PSII reaction centers in the light–adapted state (Fv’/Fm’) were lower than those of wild-type. Low temperature fluorescence analysis showed that rolling leaf mutant assigned more excited energy to photosystem I (PSI) than to PSII. The superoxide dismutase (SOD) content, soluble sugar content, proline content and malonaldehyde (MDA) content of the rolling leaf mutant were nearly 39.4, 91.2, 96.7 and 143.7% of those of wild-type, respectively. The great increase of MDA content suggests that membrane lipid system was damaged in rolling leaf mutant leaves. These results indicate that rolling leaf mutant decrease the efficiency of light utilization compared to the wild-type. This was because of the reduction of leaf area and chlorophyll contents, and the dissipation of more excitation energy as NPQ as a result of avoiding potential damage of membrane structure.
Key words: Malonaldehyde (MDA), photosynthetic characterization, rice, rolling leaf mutant.