Variation in Stomatal Traits and Photosynthetic Induction Between Subtropical Evergreen and Deciduous Broadleaved...

Under natural conditions, leaves often experience fluctuating light caused by changes in solar radiation, cloud cover, wind, and self-shading. Deciduous tree species need to complete the full cycle of vegetative and reproductive growth within a shorter growing season than evergreens. However, the differences in stomatal traits and photosynthetic induction between subtropical evergreen and deciduous tree species are still unclear. In this study, six evergreen and six deciduous angiosperm tree species were compared in terms of stomatal traits and photosynthetic induction responses. Results revealed significant interspecific variations in stomatal density (SD), stomatal size (SS), the time required to reach 50% and 90% of steady-state photosynthesis (A_area1200), and stomatal conductance (g_sarea1200) during photosynthetic induction (t_50A, t_90A, t_50gs, and t_90gs). Deciduous species exhibited higher A_area1200 and g_sarea1200 than evergreens. Additionally, SS, t_90A, and t_90gs of deciduous species were significantly lower. The faster dynamic responses to fluctuating light were closely associated with the significantly smaller SS. A strong correlation was also observed between steady-state and nonsteady-state photosynthesis across all species. These findings suggest a tight relationship between stomatal traits and photosynthetic induction rate among tree species, providing new insights into the functional strategies that enable the coexistence of evergreen and deciduous trees in subtropical forests.