An integration of photosynthetic traits and mechanisms that can increase crop photosynthesis and grain production

The hypothesis we propose is that during photosynthesis the balance between potentially detrimental and beneficial photochemically induced events can be tipped beneficially toward increased photosynthesis and toward increased crop yield. To test this hypothesis a procedure has been devised with the rice plant, Oryza sativa, that has resulted in increasing both canopy photosynthesis and rice grain yield. Two elite rice varieties selected independently in the contrasting environments of either South China or Texas, each with distinct photosynthetic traits, were crossed to produce a hybrid with an increased canopy photosynthesis and grain yield that is regularly 20 to 22% higher than the mid-yields of the parents. The photosynthetic and mechanisms which may contribute to these beneficial results in the hybrid rice are: a reduction of the midday depression of photosynthesis; a rapid development of the canopy for photosynthetic light interception and an increased canopy photosynthesis; increased amounts of carotenoids for the xanthophyll cycle; an increased protection against free radicals induced by paraquat treatment; a 6 to 12 day shorter plant reproductive life cycle; and a 8 to 10 day increase in the longevity of the flag leaf over the parents. While the hybrid rice has successfully integrated these and likely other unknown characteristics to increase both crop photosynthesis and grain yield, we propose that understanding the underlying beneficial photosynthetic mechanisms supporting these crop plant traits is worthy of thorough investigation and application in crop production.Dedicated to the memory of Professor D.I. Arnon who enriched and challenged the study of photosynthesis through a series of discoveries over 4 decades and via his force of personality.