Studies On Principles Of The Inhibition To Photosynthesis After Potato Virus Y Infection

Potato (Solanum tuberosum L) PVY is an important viral pathogen which caused a great economic loss in the potato production. It is well documented that viral infection results in reductions in assimilates and yield. In present study, we investigated the changes of ultrastructure of chloroplast and photosynthetic function in potato leaves infected by PVY.There were many virus in the chloroplast and pinwheels around the chloroplast membranes. PVY infection greatly reduced the chloroplast size and chloroplast numbers in each cell. Lowed starch content was also observed in infected leaves.PVY infection significantly reduced net photosynthetic rate together with reduced stomatal conductance, but had little influences on intercellular CO2 concentration. As the disease developed, the maximum carboxyl velocity of Rubisco, the maximum electron transport rate contributing to RuBP (ribulose-l,5-biophosphate) regeneration gradually decreased, followed by substantial reduction in the relative quantum efficiency of PS electron transport, the efficiency of excitation energy capture by open PSII reaction centers, photochemical quenching, but not with sustained photomhibition. These results suggested that PVY depressed photosynthesis mainly by interfering with the enzymatic processes in the Calvin cycle and that resulted in a down-regulation of electron transport.