Aerial environment and light quality during production affect postharvest transpiration of ornamentals

Abstract

In this study preharvest and postharvest transpiration were measured in the economically important ornamentals hydrangea (Hydrangea macrophylla), poinsettia (Euphorbia pulcherrima) and pot rose (Rosa × hybrida). Pot plants were produced under different air humidity regimes in combination with different CO2 concentrations and light qualities (visible light and UV radiation). The aim was to evaluate the preharvest and postharvest transpiration of plants developed in different climate regimes. In the study with hydrangeas the air was enriched with CO2 (800 ppm) and transpiration during growth was reduced compared to ambient (400 ppm) CO2 levels, but the postharvest transpiration was higher than that of plants grown at ambient CO2 levels. Plants produced under high RH and high CO2 had the highest postharvest transpiration. The interaction between RH and light quality was studied in poinsettias and roses. Roses were produced in moderate (60%) and high (90%) RH with different lamp types including light emitting diodes (LED), high pressure sodium (HPS) and ultraviolet (UV) lamps providing different spectral distributions. The combination of high RH and UV radiation led to higher postharvest transpiration in roses and poinsettias but no effect of UV-radiation was observed under moderate RH (60%). LED with 20% blue light improved the dark-induced stomata closure in roses produced under high RH compared to the traditional HPS lamps. Similarly, roses produced under LED with 20% blue light showed significantly lower postharvest transpiration compared to LED with 5% blue light. In conclusion, postharvest water loss is higher when the plants are produced under high RH. More blue light can improve stomatal function, but high CO2 and UV-radiation aggravate the response to high RH.