Effects of Ultraviolet-B Radiation and Acid Mist on Growth and Leaf Wettability o Radish Plants

Abstract

Radish plants were grown in chambers (PPFD 300μmol m-2 s-1, day length 14h, 21°C, 70%RH) for 10 days, under UV-B irradiation (UV-BBE; 0, 6.5 (low) and 8.6 (high) kJ m-2 d-1) for 12h a day; the plants were exposed to acid mist (pH 3.0 and 5.6) every 2 days. At the end of the treatments, leaf area, dry weights of shoot and hypocotyl, total chlorophyll content, water loss rate and water droplet contact angle (DCA), which is a measure of wettability, on adaxial and abaxial leaf surfaces were determined in each of 9 combinations of treatments, 3 (UV-B)×3 (mist, including no mist). UV-B radiation significantly decreased leaf area and dry weights of shoot and hypocotyl, and increased total chlorophyll content per unit leaf area. Similarly, acid mist of pH 3.0 significantly decreased leaf area and hypocotyl dry weight. However, no combined effect of UV-B and mist on these growth parameters and chlorophyll content was found. On the other hand, there were significant combined effects on DCA on both adaxial and abaxial surfaces; at the high UV-B level, DCA on adaxial surfaces of treated leaves with mist decreased, although that of untreated leaves increased.