Phytoalexins, Water‐stress and Stomata

Abstract

SUMMARYThere are certain features shared by phytoalexins (which can be loosely defined as microbial stress compounds) and water-stress compounds such as ABA. Therefore, a study was made to determine if phytoalexins behaved in a similar fashion to water-stress compounds and in this report phytoalexin accumulation in water-stressed leaves was investigated.Phytoalexins were not detected in mildly water-stressed leaf tissue oi Pisum sativum L. or Vicia faba L. However, if plants were severely water-stressed resulting in damaged and dead areas in their leaves, a fungi toxic substance corresponding to pisatin was detected in the damaged areas of pea leaves and, to a lesser extent, in areas which recovered full turgor, while a number of fungitoxic substances, two of which corresponded to wyerone and wyerone acid, occurred in the damaged and recovered areas of V.faba leaves.Thus, although phytoalexins may accumulate in severely water-stressed leaves they do not apparently behave in a similar manner to water-stress compounds such as ABA which would be expected to accumulate in leaves even under mild water-stress.

Phytoalexins, Water‐stress and Stomata

“…We have shown previously (Plumbe & Willmer, 1985) by thin layer chromato-graphy of extracts from severely water-stressed pea and broad bean plants that pisatin accumulated in damaged and recovered portions of pea leaves and wyerone, wyerone acid and other unidentified fungitoxic compounds accumulated in damaged and recovered portions of bean leaves. Therefore, to some extent, phytoalexins mimic 'water-stress' compounds although it must be emphasised that severe water-stress is needed before the phytoalexins can be detected.…”

Phytoalexins, Water‐stress and Stomata

“…In previous papers (Plumbe & Willmer, 1985, 1986 it was demonstrated that certain phytoalexins accumulate in severely water-stressed k-if tissue of Vicia faba L. and Pisum sativum L. and that some of the phytoalexins inhibited stomatal opening and brought about stomatal closure. The tissues of some plants also accumulate phenolics in response to attack by micro-organisms, although they are not generally considered to be phytoalexins because they are present at low levels within the tissues before infection (Link, Dickson & Walker, 1929;Harborne, 1980;Kuc, 1982).…”