Abstract: With Syringa oblata Lindl. seedling, a greening tree species in Harbin, we investigated the effects of leaf-spraying nitrate(50 mmol·L^-1 NaNO₃) on stomatal behavior and photosynthetic physiology by gas-exchange and electron microscope techniques. We analyzed stomatal distribution in upper and lower epidermis and stomatal opening as well as photosynthesis-dark respiration induction, photochemical efficiency, chlorophyll content, intercellular CO₂ concentration and stomatal conductance. The stomata and glandular hairs are distributed in the upper and lower epidermis, the effects of leaf-spraying depend on treatment time. For five-day treatment, there were no significant differences in the parameters of stomatal behavior and photosynthesis between the treated and controlled leaves. However, 14-day treatment significantly declined stomatal opening and conductance, and inhibited photosynthesis-dark respiration.

Key words: Syringa oblata seedling, nitrate, photosynthesis induction, stomatal opening, dark respiration, photorespiration