Absorption and Secretion of Polyethylene Glycol by Solanaceous Plants

Abstract

The response of the following species of the Solanaceae to water stress caused by polyethylene glycol (PEG) as an osmoticum, was examined: Solatium khasianum, S. laciniatum, S. melongena, S. nigrum, S. tuberosum, Capsicum annuum, Lycopersicon esculentum and Hyosciamus boveanus. Secretion of solution from the leaves was observed in these plants when put into 4.5% solution of PEG 1500, 4000 and 6000. Secretion of liquid started after 20 min in seedlings with mechanically damaged roots, and after 24 h in plants with intact roots. After evaporation of the liquid, deposits of white material which remained on the leaves were identified as PEG by high pressure liquid chromatography and by PEG induced protoplast fusion. All the species examined bear glandular and non-glandular hairs on their leaves. In species with leaves which are highly tomentous, PEG secretion took place mainly through the non-glandular hairs. In species with a small number of hairs, secretion took place through ordinary epidermal cells. Under similar conditions mannitol solution was secreted only through wounds and cracks, and NaCl solution was not secreted at all.