Transpiration and Water Use of Potted Floricultural Plants Under Low-light Conditions

Abstract

Abstract Potted foliage and floricultural species were evaluated for transpiration rates under low-light conditions. Environmental conditions during the experiment were 25° ± 2°C, 75% ± 10% RH, and 20 μmol·s−1 ·m−2 (400−700 nm) light intensity. Leaf cuticular and stomatal morphology were characterized with scanning electron micrographs. Coleus had the highest transpiration rate, Chrysanthemum was intermediate, and Ficus, Peperomia, and Epipremnum had the lowest transpiration rates. Abscisic acid (ABA) treatment reduced the daytime transpiration, which eliminated the diurnal fluctuation of transpiration in all species but had no effect on night transpiration, except in Coleus. Assuming complete stomatal closure at night with ABA treatment, cuticular transpiration accounts for 43% to 80% of the total transpiration rate under low-light conditions. This result points to the importance of leaf cuticular and stomatal characteristics in controlling water use of plants under low light or dark-storage. Species differed in cuticular characteristics, stomatal frequency and size, and leaf area. Stomatal frequency correlated well with transpiration rates, except in those species with unique stomatal morphologies, such as Ficus, with sunken stomates surrounded by a protruding ridge. Coleus and Chrysanthemum developed less epicuticular wax than the other species. Epicuticular and stomatal characteristics were correlated with transpiration rates of these species.