Relationship of Reproductive and Vegetative Characteristics of Pecan to Previous-season Fruit Development and Postripening Foliation Period
| Autor: | B.W. Wood |
|---|---|
| Rok vydání: | 1995 |
| Předmět: | |
| Zdroj: | Journal of the American Society for Horticultural Science. 120:635-642 |
| ISSN: | 2327-9788 0003-1062 |
| DOI: | 10.21273/jashs.120.4.635 |
| Popis: | Alternately bearing 'Cheyenne' pecan (Carya illinoensis (Wangenh.) K. Koch) trees were studied to assess the temporal aspects of previous season fruit development on several reproductive and vegetative traits of horticultural importance. Action spectra were generated and used to identify the relative sensitivities of these traits to the temporal aspects of fruiting. Based on date of maximum rate of change in sigmoidal models fitted to these action spectra, the relative sensitivity of certain important growth and developmental parameters to fruit removal time was number of distillate flowers per terminal shoot > number of distillate flowers per flower cluster on lateral shoots> length of terminal shoots > percentage of lateral shoots with fruit= catkins per terminal shoot at top of the tree> percentage of terminal shoots with fruit > catkins per standard terminal shoot> shoots produced per l-year-old branch> percentage of l-year-old shoot death. Maximum rates of change for these reproductive and vegetative parameters were typically during the dough stage of ovule development; however, substantial change also occurred for several parameters over a much wider developmen- tal window. No evidence was found for a hormone-like translocatable factor from developing fruit that either promotes or inhibits flowering. Extending the time from nut ripening to leaf drop increased production of staminate and distillate flowers the following year and appeared to increase fruit set. Fruit production by individual trees and orchards of pecan is typically variable, exhibiting a strong tendency for bienniallity at the tree and orchard level with epicycles of varying periods at regional levels (Wood, 1993b). The corollary is an impediment to the industry and growers due to unstable production, diminished nut quality during the "on" years, impaired marketing, and dimin- ished economic returns. The mechanisms regulating biennial bearing are unknown, appear to be complex, and are apparently ubiquitous in pecan. Differentiation of pistillate flowers is reported to occur by early August of the year preceding their initiation, with vernalization before the onset of rest being an absolute requirement for floret formation (Amling and Amling, 1983). The primary endogenous regulator has been theorized to be a) the level of carbohydrate reserves within the tree (Monselise and Goldschmidt, 1982; Smith and Waugh, 1938; Wood, 1989; Worley, 1979a, 1979b); b) endog- enous hormone-like growth regulators produced by the fruit or foliage (Barnet and Mielke, 1981), similar to the seed inhibitor produced by some apple cultivars (Chan and Cain, 1967); or c) a dual mechanism based on carbohydrate levels within the tree and phytohormone balances (Smith et al., 1986; Wood, 1991). From a commercial perspective, the first and last hypotheses have proven |
| Databáze: | OpenAIRE |
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