Search Results
Abstract
A resurgence of interest has been focused on the search for a chemical which would evolve ethylene after foliar application and thus induce plant growth responses. One such compound, 2-chloroethylphosphonic acid (Ethrel), has been under study as a peach thinner at the University of California orchards at Davis. It has been assumed that the peach thinning induced by Ethrel was caused by the ethylene gas which is released after application 2 . As an adjunct to the work with Ethrel, we were interested in the thinning action of ethylene gas and the resultant gross effects on the treated tree parts.
Abstract
3-CPA when applied to peach moves slowly, accumulating in the margins and veins of leaves, and the epidermal and sub-epidermal layers in the fruit and the micropylar end of the ovule. Equal degrees of fruit thinning resulted when fruit or leaves alone were treated with 3-CPA. Treating both leaves and fruit resulted in an additive thinning effect. Uniform spray coverage is emphasized to obtain uniform thinning results.
We examined an in vitro culture method for propagating unconditioned, field-grown broccoli (Brassica oleracea L. Botrytis group) from peduncle explants by testing 20 cultivars in fall and spring. Propagation was affected significantly by genotype (cultivar) and season. The percentage of explants regenerating shoots was significantly higher for cultivars grown in spring (17% to 100%) than in fall (0% to 66%). Shoot regeneration from explants of plants within a cultivar also varied significantly (0% to 100%). Additionally, the number of propagules produced per explant was influenced by cultivar and was highly correlated with the percentage of explants regenerating shoots. This method for propagating field-grown broccoli lines is useful, but its applicability can be limited by genetic and environmental factors.
Abstract
Hastened fruit maturation following MH application to apricot trees was found to be associated with MH-induced seed abortion. The time and degree to which premature abscission of seedless fruits occurred was related to time of resumption of shoot growth and to crop load. Fruits in which the seeds aborted early in the season grew like those containing seeds when competition between their growth and vegetative growth was reduced to a minimum.
Abstract
Alternate bearing in the pistachio, in contrast to other tree fruit species, is caused by abscission of abundant inflorescence buds during the heavy crop year. Bud abscission was found to increase as the number of nuts per branch increased. Branch girdling between the developing nuts on 1-year-old wood and the inflorescence buds on current wood reduced bud abscission to practically the same extent as that resulting from removing the young nuts from the branches. Application of para-chlorophenoxyacetic acid delayed but did not alter the degree of bud abscission. The greater the crop load in 1970, the shorter the shoot growth in length in 1971.
Abstract
In contrast to other fruit tree species that produce flower buds in limited quantity at the same time a heavy crop is being produced, the pistachio (Pistacia vera L.) produces abundant inflorescence buds which, for the most part, abscise during the summer. Thus, alternate bearing in the pistachio is effected by a unique mechanism. Evidence is presented which suggests that the abscission of the inflorescence buds is the result of assimilate depletion when a heavy crop is produced.
Abstract
The rate and total germination of cucumber (Cucumis sativus L.) seeds incubated at 12°C was markedly increased by acetone infusion with fusicoccin (FC). Gibberellic acid (GA4/7) was less effective than FC but more effective than GA3 or (2-chloroethyl)phosphoric acid (ethe-phon) in promoting rapid germination. Infusion of GA4/7 alone or in combination with kinetin and/or ethephon into muskmelon (Cucumis melo L.) seeds increased total germination at 16°C The growth regulators were generally not effective in promoting low temperature germination of watermelon (Citrullus lanatus (Thunb.) Matsum. & Nakai) seeds.
Measurement of substrate pH entails procurement of the substrate solution and measurement of the solution pH. Acid-base reactions are completed at the time of testing. Determination of substrate pH during development of a titration curve is more complex because it involves initially the reaction of a base with the substrate. Five factors that can influence the resulting pH values were investigated in this study and include amount of water added to substrate, method to procure substrate solution for pH determination, chemical form of base used, time allowed for acid-base reaction and the addition of CaSO4. Substrate in this study consisted of 3 sphagnum peatmoss: 1 perlite (by volume) amended with wetting agent. Dolomitic limestone (6 g·L-1 substrate) was added to substrate for the water amount and solution procurement method experiments. Except for the water amount experiment, deionized water was added by weight to achieve 95% container capacity. Dishes were incubated at 20 °C for specified times. To identify the minimal level of water necessary to ensure complete contact between base and substrate for neutralization, additions equivalent to 95%, 100%, 120%, and 150% container capacity were tested. The 95% level proved adequate. The saturated media extraction and pour-through bulk solution displacement methods for pH determination resulted in higher pH measurements in the incubated substrate than the squeeze bulk solution displacement method. This indicated that the former two methods diluted the soil solution. The squeeze method was deemed most effective. NaOH resulted in higher pH endpoints than Ca(OH)2. This was apparently due to a higher affinity of Ca2+ for peatmoss exchange sites. Since Ca2+ is the predominant cation associated with liming materials for soilless substrates, Ca(OH)2 is more appropriate for titration. From the tested incubation times of 0, 2, 4, 8, 24, 48, and 96 hours, the duration of 24 hours was found to be adequate to allow complete reaction of base with substrate acidity. The best procedure for determining pH in a substrate titration situation included a water level of 95% container capacity, Ca(OH)2 base, an incubation time of 24 hours and the squeeze solution displacement method. The additional CaSO4 was not necessary. Chemical names used: calcium sulfate (CaSO4), sodium hydroxide (NaOH), calcium hydroxide [Ca(OH)2], calcium ion (Ca2+).
Abstract
Chemical growth retardants (2-chloroethyl)trimethylammonium chloride (chlormequat), succinic acid-2,2-dimethylhydrazide (SADH, daminozide) and α-cyclopropyl-α-(ρ-methoxyphenyl)-5-pyrimidinemethanol (ancymidol) were tested on Reiger Elatior begonia ‘Schwabenland Red’ (Begonia × hiemalis Fotsch). Chlormequat applied as a spray of 0.30% active ingredient (a.i.) (1:40 dilution of commercial product) caused height retardation in high and low light periods, being most effective in the winter. A 0.30% drench was excessive under low light conditions whereas both 0.30 and 0.60% drenches were ineffective under high light conditions. No significant height retardation was found when SADH was applied as a spray at concentration up to 0.50% a.i. Ancymidol was effective as a drench at 0.125 mg per 15 cm pot under both high and low light conditions. Ancymidol sprays at concentrations up to 33 ppm were ineffective.
Abstract
The rate and total emergence of lettuce (Lactuca sativa L. ‘Empire’) seedlings incubated at 33°C for 10 hr, alternating with 23° for 14 hr, was markedly increased by seed treatment with 0.5 mM fusicoccin (FC). Neither gibberellic acid (GA) nor kinetin (K) were effective in improving emergence when used alone. The combination of FC with GA or K appeared to give a synergistic enhancement of emergence rate. The radicle elongation of seedlings was reduced by seed treatment with FC, K, or combinations of FC, GA, and K in tests at 20°. The greatest reductions were caused by combinations that included FC. The inhibiting effect of FC on radicle growth was reduced by using a concentration of 0.05 mm. Treatment with 0.05 mm FC resulted in slower emergence but gave the same total emergence as 0.5 mm FC at high temperature. Both FC and GA stimulated hypocotyl elongation.