Smart Film Impacts Stomatal Sensitivity of Greenhouse Capsicum Through Altered Light

Optical films that alter light transmittance may reduce energy consumption in high-tech greenhouses, but their impact on crop physiology remains unclear. We compared the stomatal responses of capsicum plants grown hydroponically under control glass (70% diffuse light) or smart glass (SG) film ULR-80, which blocked >99% of ultraviolet light and 19% of photosynthetically active radiation (PAR). SG had no significant effects on steady-state (gs) or maximal (gmax) stomatal conductance. In contrast, SG reduced stomatal pore size and sensitivity to exogenous ABA thereby increasing rates of leaf water loss, guard cell K+ and Cl- efflux, and Ca2+ influx. The transition between low (100 mol m-2 s-1) and high (1500 mol m-2 s-1) PAR induced faster stomatal closing and opening rates in SG relative to control plants. The fraction of blue light (0% or 10%) did not affect gs, but induced stomatal oscillations in SG plants. Increased expression of stomatal closure and photoreceptor genes in epidermal peels of SG plants is consistent with fast stomatal responses to light changes. In conclusion, light intensity was more critical than spectral quality for optimal stomatal responses of capsicum under SG, and re-engineering of the SG should maximize PAR transmission to maintain a better stomatal development. HighlightsO_LICapsicum plants grown under SG film exhibit decreased stomatal pore area, higher water loss and reduced ABA-sensitivity. C_LIO_LISG-grown plants have faster rates of stomatal closing and opening in response to light intensity changes. C_LIO_LISG increases efflux of K+ and Cl- and influx of Ca2+ of guard cells. C_LIO_LISG upregulated the expression of key genes involved in stomatal regulation and light sensing. C_LI