Leaves rapidly close their stomata after detachment resulting in a strong reduction of water loss. It has been reported that detached leaves of in vitro produced plants show continuous water loss indicating that they are unable to close the stomata properly and/or that their cuticle is malfunctioning. We examined the water retention capacity (WRC) of detached primary leaves of in vitro germinating seedlings of Vigna radiata (mungbean). It was shown that the poor WRC was most likely due to deterioration of the stomata by the high relative humidity in the headspace. Other features of the headspace, viz., O₂, CO₂ and ethylene levels, did not play a significant role. Some medium additions improved the WRC somewhat, viz., paclobutrazol and abscisic acid. Other additions such as the ethylene precursor 1-aminocyclopropane-1-carboxylic acid, the ethylene blocker silverthiosulphate and cytokinin had no or a slight negative effect.

Key words: acclimatization, micropropagation, stomata, water retention capacity.