Seasonal carbohydrate storage and mobilization in bearing and non-bearing pistachio (Pistacia vera) trees
Timothy M. Spann (1, 2, 3), Robert H. Beede (4) and Theodore M. Dejong (1)
1. Department of Plant Sciences, Mail Stop 2, University of California at Davis, One Shields Avenue, Davis, CA 95616-8780, USA / 2. Present address: Horticultural Sciences Department, Citrus Research and Education Center, University of Florida, Institute
of Food and Agricultural Sciences, 700 Experiment Station Road, Lake Alfred, FL 33850, USA / 3. Corresponding author () / 4. University of California Cooperative Extension, Kings County, 680 North Campus Drive, Suite A, Hanford, CA 93230, USA / Received February 5, 2007; accepted July 1, 2007; published online December 3, 2007
Summary
We analyzed annual carbohydrate storage and mobilization of bearing (“on”) and non-bearing (“off”) ‘Kerman’ pistachio (Pistacia vera L.) trees growing on three different rootstocks. On all rootstocks, carbohydrate storage in shoots and branches of “on” and
“off” trees was lowest following the spring growth flush. In “off” trees, stored carbohydrates increased and remained high
after the initial growth flush. In “on” trees, stem carbohydrates increased temporarily in early summer, but were mobilized
in mid-season during kernel fill, and then increased again after nut harvest. During the dormant season, the only substantial
differences in carbohydrate storage between previously “on” and “off” trees were found in the roots of the weakest rootstock.
The annual carbohydrate storage and mobilization pattern in canopy branches of heavily cropped pistachio trees appeared to
be driven by carbohydrate demands related to nut development and untempered by tree vigor. Mobilization of carbohydrates from
current-season and 1- and 2-year-old stem wood of “on” trees during the primary period of kernel fill corresponded with the
period of inflorescence bud abscission. Thus, the alternate bearing pattern associated with inflorescence bud abscission in
‘Kerman’ pistachio may be a function of mid-season mobilization of stored carbohydrates in current-season stems resulting
in stimulation of inflorescence bud abscission.
