Abstract
Metabolic changes in water content, total carbohydrates, total sugars, reducing sugars, anthocyanin, total free amino acids, proline and total indoles in shoots of "Anna" apple (Malus sylvestris, Mill) trees were investigated during dormancy and bud break under the effect of foliar application of four onion extract rates (5, 10, 15 and 20%). Flowering percentage and fruit yield characteristics (i.e., fruit-set, number of fruits tree-1 and fruit yield tree-1) were increased, while number of days recorded to reach full bloom were reduced with the application of both onion extract rates (15 or 20%). In addition, contents of total carbohydrates, total sugars, reducing sugars, anthocyanin, total free amino acids, proline and total indoles in shoots were significantly increased in floral buds, particularly during bud break. In contrast, the content of free phenols was reduced. The best results were obtained from the rate of onion extract at the level of 20% followed by 15% that could be recommended for early and high percentage of flowering and increased yield by regulating the metabolism of amino acids, including proline and indoles in apple floral buds.
Highlights
Bud dormancy in woody perennials may be a sophisticated process that allows plants to survive long periods of adverse conditions, further more because the extremes of drought, cold, and heat [1]
Onion extracts were sprayed at two equal doses, the first was sprayed before the end of dormancy, and the second was applied one week later with a volume of 4 L tree‒1 for each one in both seasons
The utmost will increases were recorded with onion extract at twentieth, that recorded 28.49 and 40.16% for fruit-setting, 12.25 and 19.39 % for fruit number and 30.50 and 24.01% for apple yield/tree among the two seasons, severally over the control trees
Summary
Bud dormancy in woody perennials may be a sophisticated process that allows plants to survive long periods of adverse conditions, further more because the extremes of drought, cold, and heat [1]. Dormancy well studied in seeds, tubers, corms, and deciduous trees. Bud break is high (>50%) once winters are cool but can drop below 20% in warm-temperate regions, with flower numbers below the economic level for crop production. Bud break is high (>50%) once winters are cool but can drop below 20% in warm-temperate regions, with flower numbers below the economic level for crop production3 This varies can modification according per the year and conjointly the area of production. In temperate perennial species a amount of low temperatures (commonly noted as winter chilling), is needed to unleash buds from endodormancy. Heat winters in several countries usually limit the productivity of temperate fruit crops 7‒10
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