Seasonal changes in pigments content in overwintering and current-year leaves of Sasa senanensis from snowmelt to before leaf-fall of canopy deciduous trees

Abstract

Abstract Sasa senanensis, an evergreen plant native to the cool temperate regions of eastern Asia, experiences both seasonal temperature fluctuations and dramatic changes in light intensity typical of understory plants. Light intensity which Sasa leaves receive surges post-snowmelt in early spring and diminishes as the canopy of upper deciduous trees develops. The current-year leaves of S. senanensis unfold under these shaded conditions, making the preservation of overwintering leaves crucial for the plant's photosynthetic productivity in early spring. To investigate how the overwintering leaves of S. senanensis adapt to the low temperatures and high light conditions of early spring; specifically, whether they adjust their antenna size or dissipate absorbed light energy as heat, we analyzed Fv/Fm and photosynthetic pigment compositions during the spring to autumn seasons from 2014 to 2017. We observed that Fv/Fm was initially low in overwintering leaves during early spring but gradually increased prior to the onset of shading, maintaining high levels under shaded conditions across all years. The chlorophyll a/b ratio rose following snowmelt and fell with increased shading in every year except 2015, suggesting that reductions in antenna size are not always essential. The quantities and de-epoxidation state of xanthophyll cycle pigments escalated post-snowmelt despite rising temperatures and subsequently decreased with shading each year, indicating that overwintering leaves adapt to early spring conditions by modifying their xanthophyll cycle pigments. This study further explores the similarities and differences in changes in Fv/Fm and photosynthetic pigments during spring between evergreen trees and S. senanensis.