Control of Auxin‐induced Stem Elongathn by the Epidermis

Abstract

Abstract Segments of the 4th and 5th internodes of light‐grown pea seedlings were used for the study of control of stem elongation. With 5th internodes, at low turgor as well as at water saturation auxin primarily appeared to cause a change in cell wall properties of the epidermis but it showed little effect on expansion af the inner tissue. This was confirmed by comparison of expansion between peeled and unpeeled segments, split tests and by measurements of stress‐relaxation properties of the epidermal cell wall. Segments with the central part re‐moved elongated well in response to auxin, but the isolated epidermis showed neither auxin‐induced elongation nor cell wall loosening. A fungal β‐1,3‐glucanase appeared, at least partly, to have a similar effect as that of auxin on elongation, by changing cell wall properties of the epidermal cell wall. Peeled segments of 4th internodes expanded very little and auxin had little effect on their epidermal cell wall properties.