(100-13) Growth light quality influences the temperature of the leaf surface via regulation of stomatal conductance and the rate of NPQ thermal dissipation
Assistant professor Jan Kochanowski University of Kielce Kielce, Swietokrzyskie, Poland
Body of Abstract: Light quality applied for indoor plant cultivation influences both the physiology and photomorphogenesis of plants. Therefore lots of efforts are made to optimize spectrum quality to improve plant growth and at the same time maximize artificial light utilization and reduce water losses via downregulation of non-photochemical thermal dissipation (NPQ) and stomatal conductance (gs). For such improvement, green (G) light supplementation to a red-blue (RB) background was successfully employed in our previous studies allowing us to restrict both NPQ and gs in plants. At the same time, however, the downregulation of NPQ and gs influences leaf temperature in opposite ways. Thus, in the present study, we analyzed the correlation between NPQ and gs levels, influenced by the growth light spectrum on the subsequent temperature (T) of the irradiated and nonirradiated leaf surface. To this end, we analyzed tomato plants (Solanum lycopersicum L. cv. Malinowy Ozarowski) grown solely under monochromatic LED lamps (438, 524 or 671 nm, 60 µmol m-2 s-1) or under mixed RGB spectrum (180 µmol m-2 s-1), and measured both adaxial and abaxial leaf surface temperature with thermocouple and thermoimaging camera. To distinguish the role of NPQ and gs, we used dithiothreitol as a potent inhibitor of NPQ rise, then we plotted a model curve of ΔNPQ or Δgs against ΔT and assessed the data fitting. Results documented, that growth light quality significantly modified the subsequent temperature of the leaf surface. Nevertheless, we found that actual leaf surface temperature is more closely related to actual NPQ activity than to stomatal conductance or transpiration rate.