Leaf microstructure and photosynthetic characteristicsof a rice midvein-deficient mutant dl-14

of the light-adapted state; F m - maximal fluorescence; F m ' - maximal fluorescence yield of the light-adapted state; F v /F m - maximal quantum yield of PS II photochemistry; F v '/F m ' - efficiency of excitation capture of open PS II center in the light conditions; F s - fluorescence intensity at any time; NPQ - nonphotochemical quenching coefficient; PAR - photosynthetically active radiation; P N - net photosynthetic rate; PS - photosystem; q P - photochemical quenching coefficient; WUE - water use efficiency; Φ PSII - effective quantum yield of PS II photochemistry. Abstract Midvein is an important structure of the upright leaf of rice, and its normal development is essential to the formation of a common plant type of rice ( Oryza sativa L.). To reveal the effect of midvein deficiency on photosynthesis-related characteristics, leaf microstructure, and vein characteristics, the photosynthetic features between the midvein-deficient mutant dl-14 and wild-type Huanghuazhan plants were analyzed. The results indicated that the midvein area of the dl-4 mutant lacked large intercellular space and instead it was filled with mesophyll cells. Moreover, the vein density of the dl-14 mutant was significantly higher than that in cv. Huanghuazhan. Chlorophyll (Chl) a , Chl b , and carotenoid content were markedly elevated in dl-14 . In terms of photosynthetic characteristics, we observed that under high irradiance and high CO 2 concentration, the net photosynthetic rate of dl-14 plants was significantly higher than that of Huanghuazhan plants, but its water use efficiency was significantly lower. In addition, several major photosynthetic parameters, including characteristics of chlorophyll fluorescence (the efficiency of excitation capture of open PS II center, photochemical quenching, effective quantum yield of PS II photochemistry, and electron transfer rate) were significantly higher in dl-14 plants compared to Huanghuazhan plants, but the nonphotochemical quenching of dl-14 mutant was significantly lower than that of Huanghuazhan. These findings indicate that the dl-14 mutant has higher vein density, stronger photon conversion ability, and weaker radiation dissipation ability. This study can provide theoretical support for breeders to use the midvein-deficient mutant.