Photosynthesis,chlorophyll fluorescence and nonstructural carbohydrates changes in husk leaves of maize in black soils region of Northeast China

Two varieties of maize (Zea mays L.) grown in fields in Black soils of Northeast China were tested to study the variation of chlorophyll (Chl) concentration, Chl fluorescence, photosynthetic parameters, and non-structural carbohydrates in husk leaves of maize. The results showed that Chl a, Chl b and total Chl concentrations increased dramatically from silking to grain filling period. Increased maximum quantum efficiency of Photosystem II primary photochemistry (Fv/Fm), potential photochemical efficiency (Fv/Fo), net photosynthetic rate (Pn), transpiration rate (E) and stomatal conductance (gs) were observed at grain filling period. The metabolic changes revealed that patterns of total soluble sugars (TSS) and sucrose were consistent with photosynthesis. Decline or a little increase of intercellular CO2 concentrations (Ci) was found for both varieties, suggesting the existence of a nonstomatal limitation of photosynthesis in husk leaves in maize. Our results suggest that PS II apparatus remained functional in senescent husk leaves and that there was a continuously efficient use of the light captured by the remaining PS II apparatus.