Relationship of Reproductive and Vegetative Characteristics of Pecan to Previous-season Fruit Development and Postripening Foliation Period

Abstract

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 developmental 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.