Journal
TREE PHYSIOLOGY
Volume 41, Issue 8, Pages 1425-1438Publisher
OXFORD UNIV PRESS
DOI: 10.1093/treephys/tpab014
Keywords
almond; bud break; bud development; defoliation; dormancy; girdling; pistachio; spring growth; starch; walnut
Categories
Funding
- California Department of Food and Agriculture (CDFA) specialty crop grant the California Pistachio Research Board
- Almond Board of California
- California Walnut Board
- Katherine Esau Fellowship from UC Davis
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Deciduous trees rely on stored non-structural carbohydrates for spring growth, with winter management of NSC playing a key role in priming trees for timely bloom. Defoliation and phloem girdling interrupt NSC accumulation and translocation, impacting spring phenology and delaying bud break in all three species studied.
Deciduous trees mostly rely on non-structural carbohydrates (NSC-soluble carbohydrates and starch) stored prior to dormancy to sustain both spring bloom and the initial phase of spring growth prior to the transition of leaves from sink to source. Winter management of NSC, their loss due to respiration, reallocation patterns and remobilization during spring, seems to be key to a timely and synchronous bloom. To assess tree dependence on NSC during dormancy, we tested whether the interruption of local branch NSC accumulation prior to dormancy by defoliation and the interruption of NSC translocation by phloem girdling influence spring phenology in three major deciduous Mediterranean nut crop species: Prunus dulcis (Mill.) D.A Webb, a hybrid between Pistacia integerrima (J. L. Stewart ex Brandis) and P. atlantica Desf. (referred to as P. integerrima), and Juglans regia L. Defoliation treatments had different effects on NSC concentration in different species depending on the time of application. However, despite the significant initial impact (increase or decrease of NSC concentration), with time this impact diminished resulting in overall similar concentrations between control and defoliated branches suggesting the presence of NSC reallocation during dormancy. Phloem girdling in P. dulcis and P. integerrima resulted in reduced export activity and greater NSC concentrations, while in J. regia girdling resulted in lower NSC concentrations, indicating that this species requires a net import of NSC during dormancy. Bud break was distinctly delayed by both defoliation and phloem girdling in all the three species, providing evidence of the significant roles that fall NSC accumulation and winter NSC management play in priming trees for spring growth resumption.
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