Abscisic Acid Accumulation in Detached Cereal Leaves in Response to Water Stress: I. Effects of Incubation Time and Severity of Stress

Abstract

The accumulation of abscisic acid (ABA) was investigated in detached leaves of cultivars of pearl millet (Pennisetum americanum [L.] Leeke), rice (Oryza sativa L.), and wheat (Triticum aestivum L.) which were partially desiccated. In millet and rice leaves stressed to a 10 per cent loss of fresh weight, ABA levels attained their maximum amounts 2 h after desiccation, and declined markedly when incubation was prolonged after 5 h. In contrast, ABA levels in wheat leaves, similarly stressed, increased to a maximum after approximately 4 h, and, compared with millet and rice, changed little over the following 20 h. In wheat leaves, ABA concentrations after 5 h of incubation increased continuously with increasing loss of fresh weight over the range 0–14 per cent. In rice, ABA levels increased with a loss of fresh weight of up to 10 per cent but did not increase further with greater stress. There was a pronounced optimum water loss (7 per cent) for maximum ABA accumulation in millet leaves. Within species there were differences between genotypes in the extent and patterns of ABA accumulation. In wheat, the cultivar TW 269/9 consistently accumulated more ABA than did Highbury under all treatments.