| A two-year study was conducted on rabbiteye blueberry var. ‘Tifblue’ to determine the effect of three concentrations of ABA (0, 20, 40, and 60 mg.L–1) and three concentrations of paclobutrazol (0, 100, 200, and 300 mg.L–1) on cold hardiness of floral parts. Two types of flower flushes were identified in ‘Tifblue’. Critical freezing temperatures and the effectiveness of the treatments were determined by conducting differential thermal analysis (DTA), electrolyte leakage, oxidative browning and tetrazolium staining. Floral parts frozen to –40C produced only one exotherm confirming that rabbiteye floral parts do not supercool. DTA results indicated that the induction of cold hardiness by ABA and paclobutrzol was concentration dependent, but this phenomenon was not noticed in viability tests. Results indicated that ABA and paclobutrazol induced hardiness in all floral parts of the second flush. ABA and paclobutrazol induced hardiness only in certain floral parts at first flush. Control treatments showed that floral parts at stage six developed in April were more prone to freezing injury compared to floral parts at stage six developed in early March. Ovaries were the hardiest followed by calyx, stamens, style and stigma, and corolla. The data indicated that the air temperature had profound influence in cold hardiness and the sequence of exotherms of DTA and LT50 of viability tests dependent on it. |
