Search Results
You are looking at 1 - 3 of 3 items for :
- Author or Editor: Rachid Hellali x
- Journal of the American Society for Horticultural Science x
Abstract
Plants of non-bud-failure (susceptible but without symptoms) ‘Nonpareil’ almond [Prunus amygdalus Batsch] produced severe bud failure (BF) symptoms internally in the growing point after 5 and 10 weeks exposure to high temperature (43°C ± 2) in a growth chamber, but not in comparable plants grown in a greenhouse at a normal temperature (about 27°C). High levels of abscisic acid (ABA) were detected in normal plants exposed to the high temperature. Buds on non-BF plants showed much lower ABA under the same conditions although there was more prior to the beginning of high temperature exposure. Little significant effects on gibberellic acid (GA)-like levels were detected.
Abstract
Shoots of ‘Nonpareil’, ‘Jordanolo’ and their hybrid progenies expressing bud-failure symptoms grew more vigorously and longer than those of normal plants. Viability of lateral buds decreased on abnormal shoots during the summer prior to bud failure, whereas those on normal shoots retained their viability. On abnormal shoots there was an increasing trend of bud-failure from the basal portion to the shoot tip. When propagated in a control nursery, buds collected from trees growing in a warmer area exhibited more bud-failure than those from a cooler zone. When shoots collected over the season from the above trees were treated with potassium salt of gibberellic acid, the inhibition of budbreak was proportional to hormone concentration; the treatment resulted in fewer bud breaks in abnormal shoots than normal ones. Bioassays of extracts from shoot apices from normal and abnormal shoots revealed large variation in hormonal levels.
Abstract
Vegetative buds from ‘Nonpareil’ almond trees affected by noninfectious bud-failure with (BF) and without (non-BF) symptoms were compared to plants without noninfectious bud-failure (normal). Samples were collected every 2 weeks from June until the following March to establish seasonal trends in weight and abscisic acid (ABA) and gibberellins (GA). Increases in bud fresh and dry weight occurred during July and August, followed by progressive dehydration up to the end of September. These changes were accompanied first by an increase in ABA and GA-like activity, and then a decrease in both hormones. During the remainder of the year (October to January) bud weight increased gradually and ABA and GA were low. Buds from BF and non-BF plants increased in weight in July and August, but much less than the normal. ABA levels were much less than from the normal, but the GA activity was comparable to normal. BF symptom development is characterized by lower production of ABA during the critical July-Aug. period. A disruption of the normal rest induction and recovery pattern was also hypothesized.