Studies were conducted over eight location-years to evaluate the effects of rowcover material, time of application, and time of removal on `Heritage' red raspberry cane growth, flowering, and fruiting. We anticipated that rowcovers would accelerate fruit maturity so that more of the crop could be harvested before the onset of cold temperatures in autumn. In seven of the eight experiments, rowcovers either increased yields or accelerated harvest. With a March application, harvest began 3 weeks earlier, and August yields of covered plants were 42 times higher than those of noncovered plants. Responses were observed with spunbonded polypropylene and polyester covers, but not with polyethylene covers. Rowcovers placed over the row before primocane emergence and removed when canes were ≈50 cm tall resulted in the greatest plant response. The use of polyester or polypropylene rowcovers with primocane-fruiting raspberries appears to be economically feasible in most years in northern climates.
Fruit temperature of persimmons (Diospyros kaki L. f. cv. Hiratanenashi) was regulated at a constant 14, 22, or 30C during growth stage III. Fruit growth and ripening were greatly accelerated at 22C compared with control fruit grown at ambient air temperature (range 9.3 to 28.5C). At harvest (30 days after treatment), fruit kept at 22C was much heavier, more deeply colored, and softer than the controls. In contrast, 30C delayed the onset of rapid fruit expansion and ripening. At harvest, however, the fruit, though still green, were about the same size as tbe controls. With the exception of rapid chlorophyll degradation, 14C had little effect on fruit growth and ripening. Little difference in sugar content and composition was found between temperature treatments and controls.
For accelerating the filling in of bare areas in native lowbush blueberry fields or converting new areas to production, micropropagated plantlets rooted after three subcultures outperformed seedlings and rooted softwood cuttings. After 2 years of field growth, they averaged 20.3 rhizomes each of average dry weight 3.5 g, as compared with 5.7 rhizomes of average dry weight 1.1 g for rooted softwood cuttings. After 1 year of field growth, seedlings produced on average 3.3 vs. 0.4 rhizomes from micropropagated plants that had not been subcultured and 0.3 rhizomes from stem cuttings. Apparently, subculturing on cytokinin-rich media induces the juvenile branching characteristic that provides micropropagated plants with the desirable morphologies and growth habits of seedlings. These characteristics favor rhizome production while the benefits of asexual reproduction are retained. The advantage in rhizome production of micropropagation over stem cuttings varied among clones.
Abstract
Lilium longiflorum Thunb. ‘Nellie White’ flower buds developed from visible bud to open flower more rapidly at constant 27°C than at constant 15°. This increased growth rate was most pronounced when buds were less than 6 cm. Once buds were greater than 10 cm, the differences in rate of flower bud growth at 15° compare to 27° was insignificant. Bud development was biphasic, with a relatively slow growth rate up to 6 cm and then an accelerated rate from 6 cm to open flower. The fitted regression line for buds less than 6 cm was: days to flower (DTF) = 37.969 - 8.945 Ln [bud length (L)] — 0.453 [(Temperature (T)]; for buds greater than 6 cm: DTF = 33.258 — 2.039 (L) - 0.736 (T) + 0.044 (L x T). The correlation coefficients for the 2 equations were respectively: r = 0.82 (R 2 = 0.67) and r = 0.93 (R 2 = 0.87).
Root zone inoculation with P-solubilizing Penicillium bilaji (PB) has increased P uptake and yields of several field crops. We examined the influence of applying 0 - 5 × 105 C.F.U./plant of PB to geranium and petunia grown in the greenhouse in a low P soil amended with rock P. All rates of inoculation increased growth and enhanced flowering of both crops. A second study examined the interaction between PB and rock P amendments in poinsettia. Inoculation with PB accelerated growth through to pinching as did addition of rock P to the media. The combined PB + rock P treatment enhanced bract development resulting in better red color at market time. These results suggest that PB inoculation can enhance growth and/or improve P use efficiency in greenhouse crops.
Abstract
Fruit and leaf explants of ‘Pineapple’ orange were aged for 2 to 36 hr after excision and prior to treatment with ethylene or 2,4-dichlorophenoxyacetic acid (2,4-D). Abscission of fruit explants, aged for various durations, was accelerated by ethylene applied as early as 2 hr after excision but was delayed by 2,4-D administered within 26 hr after excision. Leaf explants did not exhibit an abscission response to ethylene up to 20 hr following excision, but they became responsive at 28 hr. The growth substance, 2,4-D, was effective in delaying abscission of leaf explants aged for 44 hr. Ethylene, 2-chloroethylphosphonic acid (Ethrel), and cycloheximide failed to accelerate abscission in young ‘Valencia’ orange fruit (3.1 to 3.8 cm diam.) while they greatly accelerated abscission in mature fruit. Citrus leaf, but not mature fruit explants, exhibit the 2-stage abscission phenomenon in response to auxin and ethylene. Results suggest the possibility of differential abscission promotion in mature vs immature ‘Valencia’ orange fruits.
Abstract
Orchard production systems have experienced rapid and dramatic changes over the past 3 decades in both the techniques and geno-types used. We expect this rate of change to accelerate in the future. As production costs escalate, the demand will become ever stronger for systems providing early, heavy, reliable yield fo high-quality, easy-to-harvest fruit. These systems must, however, be reasonably priced and durable. The grower will be less able to afford tree losses, whether due to biotic, climatic, or edaphic hazard, and will need to economize on use of machinery and chemical pesticides. Growth regulators will be employed only where there are effective, economically justified, and environmentally acceptable.
Jews' Mallow (Melokhia) Corchorus olitorus, is a very important leafy vegetable for the Egyptians all year round, except for winter period. Short days and low temperatures accelerate the flower initiation and inhibits the vegetative growth entirely. Some supplimentary light of 8000 lux for one or two hours after sun-set, or as a flash for 10 min. at mid-night have been tried. The obtained results showed that two hours of artificial light after sun set inhibits the flowering and encourages leaf number, leaf area, plant height, plant fresh and dry weight, and leaf/height ratio. The obtained data were discussed in relation to the prevailed microclimatic conditions.
Abstract
Seed germination of pepper (Capsicum annuum L.) in aerated water columns was accelerated and germination uniformity improved by using gibberellic acid (GA3) at 6 μg/mg seed with 50 to 75 mg seed/ml of solution. Higher GA3 rates in the aerated columns reduced germination percentage in some cultivars. Detrimental effects for GA3 up to 6 μg/mg seed were not observed and in some cultivars speed of emergence and seedling growth was stimulated. GA3 is economically feasible for use in germinating pepper seeds for sowing using the fluid drilling technique.
Abstract
An antitranspirant (AT) applied 2 3 weeks before harvest accelerated olive (Olea europaea L., cv. Manzanillo) fruit growth and led to larger fruit at harvest. The fruit-enlarging effect was detected within 1 day of application. A simulated rain also increased fruit size, but much of the gain in size was lost as soon as the “rain” was terminated. Daytime fruit shrinkage was reduced significantly with the AT. At harvest, fruit moisture was higher in AT-treated fruits, and after harvest the water lost from fruits was lower. When AT was substituted for the last pre-harvest irrigation, fruit size was increased.