ABSTRACT
Floral and vegetative plant parts from ‘Climax’ rabbit-eye blueberry (Vaccinium ashei Reade) were collected in the fall and winters of 1986-87 and 1989-90 before and after various accumulations of chilling, recorded either as chill units (CU) or chilling hours (CH). Concentrations of abscisic acid (ABA) and indoleacetic acid (IAA) were determined by enzyme-linked immunoassays. Prior to chilling, ABA accumulations were highest in vegetative and flower buds, lowest in the leaves, and intermediate in terminal stems. Vegetative bud ABA content remained high until mid-February when 690 62CH had accumulated. Flower bud ABA content decreased rapidly with minimal CH accumulations (90-380 CH) and then slowly decreased with additional chilling. Individual flower bud dry weight increased 0.03 mg per day from 29 October (CU = 0) to 09 December (CU = 90). Between 09 December and 05 January (CU 450), dormancy was most intense with flower buds increasing only 0.01 mg per day in weight. Flower bud weight increased 0.11 mg per day between 05 January and 20 January (CU = 600). Content of IAA in flower buds decreased between 0 and 90 CU, remained relatively constant between 90 CU and 450 CU and then increased rapidly between 450 and 600 CU collection dates. There was a large increase (≈ 2X) in the ratio of IAA:ABA in the flower buds at the 600 CU date and this corresponded to about a 10-fold increase in daily per bud dry weight gain. These data suggest that IAA levels or the ratio of IAA to ABA may be associated with the regulation of flower bud break in ‘Climax’ rabbiteye blueberries.[Article copies available from The Haworth Document Delivery Service: 1-800-342-9678.]
