Search Results
Abstract
Levels of free and hydrolyzable abscisic acid (ABA, H-ABA) in vegetative apple (Malus domestica Borkh.) buds were measured by electron capture gas chromatography. ABA level was high during midsummer both before and after entry into dormancy, increased to a maximum just prior to leaf fall, and decreased to a minimum just prior to bloom. H-ABA level was low during midsummer, increased gradually during fall and winter, reached a maximum during the early stages of bud development, and then decreased very rapidly just prior to full bloom.
Abstract
Chilling-temperature response curves were obtained by testing seed germinability at 25°C after 0 to 2880 hr (120-hr intervals) of stratification at temperatures from −4° to 16°. The curves of the species tested were bellshaped with a definite skew to the cold side in some species. Some activity was detected at −2° and at 16°, the approximate limiting temperatures of the process. Dormancy was broken most rapidly at 4° in seeds of P. persica, P. communis (cold climate source), P. avium, P. mahaleb and M. domestica, whereas 6° was more effective in P. armeniaca, C. oblonga, and P. communis (warm climate source). The data were used to define a stratification degree hour and develop a stratification model for the seed of these species.
Abstract
[14C-ethyl] labeled (2-chloroethyl)methylbis(phenylmethoxy)silane (CGA-15281) was applied to fruit and leaves of 4-year-old ‘Bicentennial’ peach trees [Prunus persica (L.) Batsch]. Virtually none of the parent material moved into the fruit or was taken up and transported in vegetative tissue. Of the small amount found within the vegetative tissue, there was equal distribution between acropetal and basipetal movement. The compound appears to act through the release of ethylene which penetrates the tissue rather than uptake of the parent molecule and subsequent release.
Abstract
Temperature treatments influenced inception, intensity and termination of rest in peach trees [Prunus persica (L.) Batsch]. A substance that affected the response was translocated within the trees. The time of leaf abscission in the fall was related to duration and intensity of rest in ‘Gleason Elberta’ peach leaf terminal buds. An August application of 100 ppm gibberellic acid (GA3) and warm field temperatures delayed defoliation and extended rest.
Abstract
Abscisic acid (ABA) metabolism of 6-week-old seedlings of cool- and warm-season crops was determined after a 24-hr exposure to supra- and sub-optimal temperatures. Plants were grown at 25°C and then exposed to 10, 25, or 40°C. After a 24-hr exposure, free (FABA) and hydrolyzable (HABA) abscisic acid and dihydrophaseic acid (DPA) were measured in the plant tops by gas chromatography. Warm-season crops, exposed to 10°C exhibited elevated levels of FABA, HABA and DP A compared to those plants exposed to 25 or 40°C. Among cool-season crops, only peas had higher FABA and HABA levels at 40°C than at 10 or 25°C, while beets had lower levels of HABA at 25°C than at 10 or 40°C. DPA existed at much higher concentrations than FABA and HABA in all plants. The increases in ABA and DPA in warm-season crops exposed to 10°C are attributed to low temperature stress.
Abstract
Abscisic acid (ABA) concentrations were significantly higher in young leaves of N-deficient (stressed) plants of tomato (Lycopersicon esculentum Mill.) both at day 2 and day 7 after transfer to a N-free Hoagland's solution. In old leaves, N-deficiency significantly increased ABA concentrations after 2 days but not after 7 days.
Rowcovers were placed over `Himrod' grapes during the 1992 and 1993 growing seasons to test the feasibility of manipulating the microclimate temperature sufficiently to bring the covered grapes into full bloom and harvest earlier. The rowcovers were removed from the grapes after fruit set each year. In 1992, the covered grapes bloomed 18 May, 6 days earlier than the open blocks. In 1993, full bloom in the covered grapes occurred on 29 May, 9 days earlier than the controls. However, the advanced bloom of the covered grapes did not result in the expected earlier maturity when compared to the uncovered grapes. Covered grapes did attain a soluble solids maturity index of 18 two to three days earlier than uncovered grapes.