Water stress abscisic acid content

Figure 6. Decrease in abscisic acid content of wilted leaves of Xanthium after stress was relieved. Detached leaves were wilted by reducing the fresh weight by 10%. Stress was relieved after 5 hr by submerging leaves into distilled water for 5 min.

Zeevaart JAD (1971) ( + )-Abscisic acid content of spinach in relation to photoperiod and water stress. Plant Physiol 48 86-90... 

When subjected to drought stress, excised wheat Triticum aestivum L.) leaves increase ethylene production as a result of an increased synthesis of ACC 71 and an increased activity of the ethylene-forming enzyme (EFE) which catalyzes the conversion of ACC 71 to ethylene. Rehydratation to relieve water stress reduces EFE activity to levels similar to those in non-stressed tissue. Pretreatment of the leaves with N-benzyladenine (BA) 75 or indole-3-acetic acid lAA 76 prior to drought stress caused further increase in ethylene production. Conversely, pretreatment of wheat leaves with abscisic acid ABA 77 reduced ethylene production to levels of non-stressed leaves, accompanied by a decrease in ACC 71 content, Eq. (29). 

Effects on Abscisic Acid, One of the most clearly defined effects of water stress (decreased turgor) on hormones is the enhancement of ABA biosynthesis in leaves (Wright and Hiron 1972, Milborrow 1974, Zeevaart 1980). The response is rapid and the increase in ABA content is large (Kriedemann et al. 1972, Milborrow 1974, Wright and Hiron 1972, Hiron and Wright 1973). Water stress-induced enhancement of ABA content also occurs in roots (Walton et al. 1976) but the effect is small in some cases (Milborrow and Robinson 1973). 

---