Tobacco plants (Nicotiana rustica L.) pre-exposed to leaf dehydration, mineral deprivation, salination, or BO(3) (3-) toxicity exhibited increased resistance to subzero temperature and to reduced oxygen in the root medium. The stressed plants all showed an elevated content of leaf abscisic acid. Upon transfer of mineral deprived and salinated plants to prestress conditions, a decline in leaf ab...

This research focused on studying how light and endogenous abscisic acid regulate leaf development in Hippuris vulgaris, a species of heterophyllic aquatic plant. Amounts of photosynthetically active radiation greater than 300 micromoles per square meter per second caused submerged H. vulgaris shoots to produce aerial-type leaves. Abscisic acid was not detected in shoots grown under noninducing...

The effect of abscisic acid on the exudation rate from decapitated roots of sunflower plants (Helianthus annuus L.) was investigated in the presence and absence of an imposed hydrostatic pressure gradient. The magnitude of the abscisic acid effect was constant even when suctions up to 60 cm Hg were applied to the cut stumps.When roots were bathed in a THO-labeled nutrient solution, the course o...

Etiolated hypocotyls of the resistant soybean (Glycine max [L.] Merr.) cultivar Harosoy 63 became susceptible to Phytophthora megasperma (Drechs.) f.sp. glycinea (Hildeb.) Kuan and Erwin race 1 after treatment with abscisic acid. Susceptibility was expressed by increases in lesion size and a major decrease in accumulation of the isoflavonoid phytoalexin, glyceollin. In untreated hypocotyls, act...

Berries on field-grown Vitis vinifera cv. Doradillo were treated at different times during stage II with benzothiazole-2-oxyacetic acid or 2-chloroethylphosphonic acid, and measurements were made of their growth and hormone content. The concentration of ethylene was low during stage II and declined as berries ripened. Both 2-chloroethylphosphonic acid and benzothiazole-2-oxyacetic acid caused i...

Discussion The evidence presented here and previously (Neill et al., 1982a,b) strongly suggests that 1 ‘-deoxyabscisic acid (111) is the immediate precursor of abscisic acid in C. rosicola. Feeding studies have shown that 2-cis-a-ionylidene ethanol (I) and 2-cis-a-ionylidene acetic acid (11) are converted in good yield into 111 and abscisic acid. Thus they can be utilized as biosynthetic precur...

Extracts from ripe fruit and seeds of Sorbus aucuparia inhibit germination of other seeds, tested with Amaranthus caudatus and Lepidium sativum. The main compound of the “neutral fraction” of fruit extracts is the lactone compound parasorbic acid (4 —7 mg/g fresh weight) which inhibits germination at concentrations > 5x1C T 4 m. The “acid fraction” contains abscisic acid (1 .3—2.5 ^ / g fresh w...