Response of plasmodesmata formation in leaves of C₄ grasses to growth irradiance

Abstract

Rapid metabolite diffusion across the mesophyll (M) and bundle sheath (BS) cellinterface in C4leaves is a key requirement for C4photosynthesis and occurs viaplasmodesmata (PD). Here, we investigated how growth irradiance affects PDdensity between M and BS cells and between M cells in two C4species using ourPD quantification method, which combines three‐dimensional laser confocal fluores-cence microscopy and scanning electron microscopy. The response of leaf anatomyand physiology of NADP‐ME species,Setaria viridisandZea maysto growth under dif-ferent irradiances, low light (100μmol m−2s−1), and high light (1,000μmol m−2s−1),was observed both at seedling and established growth stages. We found that theeffect of growth irradiance on C4leaf PD density depended on plant age and species.The high light treatment resulted in two to four‐fold greater PD density per unit leafarea than at low light, due to greater area of PD clusters and greater PD size in highlight plants. These results along with our finding that the effect of light on M‐BS PDdensity was not tightly linked to photosynthetic capacity suggest a complex mecha-nism underlying the dynamic response of C4leaf PD formation to growth irradiance.