© 2007 Heron Publishing—Victoria, Canada
Preformation in vegetative buds of pistachio (Pistacia vera): relationship to shoot morphology, crown structure and rootstock vigor
Timothy M. Spann (1–3), 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: University of Florida, Institute of Food and Agricultural Sciences, Citrus Research and Education Center,
700 Experiment Station Road, Lake Alfred, FL 33850, USA / 3. Corresponding author (spann@crec.ifas.ufl.edu) / 4. University of California Cooperative Extension, Kings County, 680 North Campus Drive, Suite A, Hanford, CA 93230, USA / Received July 24, 2006; accepted December 6, 2006; published online May 1, 2007
Summary
Effects of rootstock, shoot carbohydrate status, crop load and crown position on the number of preformed leaf primordia in
the dormant terminal and lateral buds of mature and immature ‘Kerman’ pistachio (Pistacia vera L.) trees were investigated to determine if rootstock vigor is associated with greater shoot preformation. There was no significant
variation in preformation related to the factors studied, suggesting strong genetic control of preformation in ‘Kerman’ pistachio.
The growth differences observed among trees on different rootstocks were associated with greater stimulation of neoformed
growth in trees on the more vigorous rootstocks. However, most annual extension growth in mature tree crowns was preformed,
contrasting with the relatively high rate of neoformation found in young tree crowns. Large amounts of neoformed growth in
young trees may allow the trees to become established quickly and secure resources, whereas predominantly preformed growth
in mature trees may allow for continued crown expansion without outgrowing available resources. We hypothesized that the stimulation
of neoformed growth by the more vigorous rootstocks is associated with greater resource uptake or transport, or both. Understanding
the source of variation in shoot extension growth on different rootstocks has important implications for orchard management
practices.
Keywords:
bud dissection, crown development, leaf primordia, neoformation, shoot extension growth.
