EFFECTS OF UREA AND PLANT BIOREGULATORS (ETHEPHON AND PROMALIN®) ON TISSUE NITROGEN LEVELS, COLD HARDINESS, AND CROPPING OF SWEET CHERRY TREES
In deciduous fruit trees, reserve N is known to play an important role in early season growth and flower bud development, but little information is available in sweet cherries.
To improve tree reserve N, we sprayed four-year-old Lapins/Mazzard trees with urea at 0, 2, 4 or 6% on 25 Sept and 2 Oct 2000. Ethephon (200 ppm) as a leaf senescence promotor or Promalin® (250 ppm BA + 250 ppm GA4+7) as a senescence delaying agent was applied to some of the trees on 22 and 28 Sept with the objective of studying how plant bioregulator (PBR)-altered leaf senescence/abscission affects N recovery from leaves.
Urea sprays increased total N concentration in leaves and dormant woody tissues including flower buds and shoots. Ethephon significantly advanced leaf senescence and defoliation, resulting in improved leaf N recovery. In contrast, Promalin substantially delayed leaf senescence and defoliation, leading to reduced N recovery. Accordingly, N concentration in dormant shoots was increased by ethephon but decreased by Promalin. Flower bud N concentration was reduced by ethephon but increased by Promalin. The Promalin treatment resulted in larger and more advanced buds. The ethephon treatment had the opposite effect.
Time of bloom was delayed slightly by ethephon and advanced by Promalin, each by about one day compared to the unsprayed control. Cold hardiness of flower buds in early winter and early spring was unaffected by urea but was increased slightly by ethephon (low-exotherm temperatures were -20.0 vs. -18.5 °C in December; -15.0 vs. -13.8 °C in March). Interestingly, despite advanced bud development in the treated trees, Promalin did not affect flower bud hardiness at either time. Shoot hardiness in December, assessed by visual injury to xylem tissues, was unaffected by urea but was reduced substantially by the Promalin treatment (by about 6°C) and was increased slightly by ethephon. Fruit set was unaffected by urea but was increased significantly by Promalin treatment compared to the no PBR control (136 fruits versus 95 fruits per 100 floral buds).
Urea sprays increased total N concentration in leaves and dormant woody tissues including flower buds and shoots. Ethephon significantly advanced leaf senescence and defoliation, resulting in improved leaf N recovery. In contrast, Promalin substantially delayed leaf senescence and defoliation, leading to reduced N recovery. Accordingly, N concentration in dormant shoots was increased by ethephon but decreased by Promalin. Flower bud N concentration was reduced by ethephon but increased by Promalin. The Promalin treatment resulted in larger and more advanced buds. The ethephon treatment had the opposite effect.
Time of bloom was delayed slightly by ethephon and advanced by Promalin, each by about one day compared to the unsprayed control. Cold hardiness of flower buds in early winter and early spring was unaffected by urea but was increased slightly by ethephon (low-exotherm temperatures were -20.0 vs. -18.5 °C in December; -15.0 vs. -13.8 °C in March). Interestingly, despite advanced bud development in the treated trees, Promalin did not affect flower bud hardiness at either time. Shoot hardiness in December, assessed by visual injury to xylem tissues, was unaffected by urea but was reduced substantially by the Promalin treatment (by about 6°C) and was increased slightly by ethephon. Fruit set was unaffected by urea but was increased significantly by Promalin treatment compared to the no PBR control (136 fruits versus 95 fruits per 100 floral buds).
Guak, S., Beulah, M., Neilsen, D., Quamme, H.A. and Looney, N.E. (2005). EFFECTS OF UREA AND PLANT BIOREGULATORS (ETHEPHON AND PROMALIN®) ON TISSUE NITROGEN LEVELS, COLD HARDINESS, AND CROPPING OF SWEET CHERRY TREES. Acta Hortic. 667, 453-460
DOI: 10.17660/ActaHortic.2005.667.65
https://doi.org/10.17660/ActaHortic.2005.667.65
DOI: 10.17660/ActaHortic.2005.667.65
https://doi.org/10.17660/ActaHortic.2005.667.65
Prunus avium, differential thermal analysis (DTA), leaf senescence, defoliation, time of bloom, fruit set
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