Studies on Plant Response to Rainfall

Abstract

The effect of mist treatment on dry matter production in some crop leaves was investigated on sunny days in the greenhouse and in the phytotron. Kidney bean (Phaseolus vulgaris L.), pea (Pisum sativus L.), soybean (Glycine max Merr.), sweet potato (Ipoemea batatas Lam.), Chinese mustard (Brassica chinensis L.) and maize (Zea mays L.) were used as the materials. The rate of dry matter production was measured by using the improved half-leaf method. The results were as follows:1) On sunny days, water mist treatment decreased the rate of dry matter accumulation in these crop leaves in the greenhouse. The rates under mist treatment were about 50% of those under no mist condition in soybean, Chinese mustard and maize leaves, and 70-80% in pea, kidney bean and sweet potato leaves (Figs. 1 and 3).2) Deionized water mist treatment also decreased the rate of dry matter accumulation of maize leaves in the phytotron (Fig. 4).3) In maize leaves, the ratio of accumulation rate under mist to that under no mist decreased with increasing solar radiation from 133W/m2 to 465W/m2 (Table 1). This tends to show that the greatest decrease of dry matter accumulation occurred at the highest intensity of radiation.4) The inhibitory effect of mist on dry matter accumulation differed with the ratio of stomata number on the upper surface of leaves to that on the lower surface. The accumulation of leaves with the higher ratio was more strongly inhibited than that with the lower ratio.5) In the greenhouse on sunny days, mist treatment decreased air- and leaf-temperatures markedly (Table 2 and Fig. 2). Under mist condition, the leaf temperatures showed somewhat higher values than the air temperatures. Differences between the air and leaf temperatures were larger under mist condition than under no mist condition.