Transpiration and stomatal opening of x-irradiated broad bean seedlings

Abstract

Transpiration, stomatal opening and osmotic pressure of epidermal and guard cells were measured in non-irradiated Vicia faba seedlings and at various times following exposure to 250 R of 230 KVp X-ray. Significant reduction in total daily water loss per plant was detected in irradiated plants which was largely associated with substantial inhibition of leaf proliferation and growth; however, water loss per unit leaf area was significantly reduced in irradiated plants at 14–16 days post irradiation. The reduced transpiration was associated with inhibition of stomatal opening from the 9th to 16th day after irradiation. The osmotic pressure of epidermal and guard cells was compared in control and irradiated plants ; the osmotic pressure of epidermal cells in irradiated plants appeared to be slightly higher than that of epidermal cells of non-irradiated plants. However, the slight osmotic pressure changes of epidermal cells in irradiated plants did not appear to be a major factor contributing to inhibition of stomatal opening in irradiated plants under the growth conditions of the experiments.