Evaluation of the Heterosis on Leaf Photosynthesis of Remote‐Cross F1 Rice (Oryza saliva L.)

Abstract

AbstractThe heterosis of leaf photosynthesis was studied on the main characters included in the range from CO2exchange rate (CER) to enzymatic activity using a remote cross F, rice. The CER was significantly higher than those of the parental strains, showing a 111 % heterosis effect on average; at the same time strong heterosis was observed for the leaf area production and growth. Also stomatal and mesophyll conductances increased in the F1 rice, which may contribute to the increase in CER. Chlorophyll content (Ch1), soluble protein content (SPC) and ribulose 1,5‐bisphosphate (RuBP) carboxylase activity (RCA) were measured as the internal factors related to photosynthesis, and compared between the F1, rice and the parents. For all these factors, the F1 rice showed low values compared to the parents. Positive heterosis was not expressed here. On the other hand, the specific activity of RCA (RCA/SPC) increased in the F1, rice, showing a 120% heterosis effect. This may be regarded as one of the main causes for the increase in CER of the F1, rice. High CER expressed as heterosis concurrently with large leaf area production is one of the important findings in our study, and this may suggest a high possibility of further improvement in biomass production or yield of rice by gathering the advantageous elements into a hybrid plant.