Growth Inhibition and Seedling Injury in Response to UV Spectra and Irradiation Timing in Plug-transplants of Pepper (Capsicum annunm L.) and Tomato (Solanum lycopersicum)

Abstract

The objectives of this study were to determine the effects of UV spectra (broad UV 274-400 nm, B-UV or filtered UV 286-400 nm, F-UV) and irradiation timing (at day or night) on growth inhibition and seedling injury in plug-transplants of pepper (Capsicum annunm L. 'Nogkwang') and tomato (Solanum lycopersicum, 'Pinktop'). We investigated some parameters, to clarify the plant response, such as ion leakage, lipid peroxidation, chlorophylls, careotenoids, photochemical efficiency, UV absorbing compound, plant growth, and flowering. The results showed that irradiation of B-UV at night significantly inhibited plant height and total leaf area in two species. However, it caused seedling injuries such as leaf necrosis and bloomlessness regardless of irradiation timing. While irradiation of F-UV did not cause any seedling injury regardless of irradiation timing, it significantly inhibited plant height by 25.4% in pepper and by 26.1% in tomato. Our results suggest that irradiation of F-UV at night may be desirable to control excessive stem elongation in plug-transplants during summer, in addition to being safe to the grower.