Studies on the Hydrophysiological Rhythms of Citrus Trees

I. Cyclic Fluctuations of Leaf Thickness and Stem Diameter of Natsudaidai Seedlings

Abstract

Cyclic fluctuations in leaf thickness and stem diameter were examined with a differential transformer.
Variations of leaf temperature followed the cyclings. Thus it was postulated that transpiration as well as stomatal aperture might change periodically.
When the water condition was disturbed, cyclic oscillations of both leaf thickness and stem diameter were weakened or disappeared. The Natsudaidai seedlings in a condition of water stress responded quickly to rewatering and consequently the cyclic oscillations recovered.
Above 70 per cent relative humidity, the cyclings were not observed but below 65 per cent they reappeared.