Effects of forced ventilation at different relative humidities on growth, photosynthesis and transpiration of geranium plantlets in vitro

Abstract

Shoots of geranium (Pelargonium × hortorum Bailey ’Hollywood Red’) were cultured under forced ventilation with air of different relative humidities (RH). In comparison with those grown under conventional in vitro conditions, plantlets grown under forced ventilation had greater dry weight of both shoots and roots. Grey pigment zonation, which appears on leaves grown in either the greenhouse or the field, was not observed on leaves cultured under conventional in vitro conditions but was found on leaves cultured under forced ventilation. Forced ventilation at 100% RH, or at 100% RH before rooting and 46% after rooting, did not have a significant effect on the photosynthetic capacity of leaves. However, leaves grown at 46% RH after rooting showed a much lower transpiration rate than leaves grown under conventional in vitro conditions or in vessels ventilated with air of 100% RH. Key words: Pelargonium × hortorum, micropropagation, forced ventilation, growth, photosynthesis, transpiration