Enhancing ATP Formation to Increase Photosynthesis

Abstract

ATP is the necessary component of assimilation power in photosynthesis. It is not only required for CO2 assimilation but also for the maintaining of the operation of the photosynthetic apparatus, such as for the activation or phosphorylation of several kinds of enzymes or other proteins. It is widely accepted that the reduction of NADP+ by the photosynthetic noncyclic electon transfer is coupled with the formation of ATP. The ATP/NADPH ratio is generally considered to be 1.33, which is lower than the ratio required for the assimilation of one molecule of CO2 to carbohydrate level. The insufficient amount of ATP is believed to be supplemented by cyclic or pseudocyclic photophosphorylation (PSP), though there is still debate about which way is more important. In our lab, we showed by several kinds of experiments that in many cases the photosynthesis was often limited by ATP supply, and might be enhanced by two kinds of measures. One is to improve the coupling efficiency by some treatments, such as increasing the concentration of phosphate or polybasic acids, or adding some coupling efficiency improvers. The other way is to increase cyclic PSP by applying adequate amount of PMS solution to the leaves. Recently, we found that spraying 1-2 mM of NaHSO3 solution to the leaves could also enhance cyclic PSP in vivo, which was indicated by increase of the ms-delayed light emission, P700 turnover and post-illumination fluorescence of chlorophyll. As NaHSO3 is very cheap and has no harmful effect at such low concentration, it is hopeful that it could be used as a practical measure in agricultural production. In some experiments, when NaHSO3 was sprayed on wheat or rice leaves during early stage of ripening, the photosynthesis was increased by more than 10% for several days and the yields of harvest were increased by 10%.