Seasonal changes of leaf chlorophyll content as a proxy of photosynthetic capacity in winter wheat and paddy rice

•Vcmax25, Na and Chla of winter wheat and paddy rice exhibited distinguishable seasonality.•The seasonality of leaf Na and Chla were inconsistent with that of Vcmax25.•Differentiating pre- and post-flowering stages significantly improved the estimation of Vcmax25 from Chla.