You are looking at 1 - 10 of 43 items for
- Author or Editor: Miklos Faust x
At the beginning and near to the end of the endodormant period, cytokinin-type growth regulators are effective to end dormancy in apple. The same growth regulators are not effective during the middle of this period. Terminal buds require less chilling than lateral buds to emerge from the dormant period. Lateral buds on decapitated shoots also require less chilling, indicating that auxin may be involved in dormancy. Replacing the terminal with IAA keeps water in bound state in the lateral buds, indicating the effect of IAA in dormancy. We have developed the theory that the beginning and the end of the winter-dormant period is governed by apical dominance. It appears that only this period can be manipulated either with dormancy avoidance methods or with dormancy-breaking chemicals. The central portion of the dormant period is not subject to manipulation. Therefore, it is important that the depth of the dormancy is quantified. Certain growth regulators can be used for determining the state of bud dormancy. Thidiazuron gives results within 2 to 4 days.
Orchard trees grow and produce in one place for 15 to 50 years. By the time they are bearing, they have extensive root systems and are able to exploit nutrients of the soil efficiently. How and when nutrients should be supplied to the tree distinguishes fruit nutrition from other branches of nutritional science. During the past 75 years tree-nutrition developed from an uncomplicated method of replacing used nutrients to the soil to an intricate science which requires the total understanding of the physiology of the tree and which is completely integrated into the management practices of the orchard. This review follows the changes which led to the development of “tree-nutrition” as we know it today.
There are two philosophical points of view regarding the most effective approach to research. One holds that coordinated research is more productive and attains its goals faster with less cost. The Manhattan Project and Space Flights are cited as proof that coordination is the only effective way to solve problems. The other point of view is that good researchers know what to do without coordination. Supporters of this view claim that all major discoveries have resulted from individual efforts and that agricultural research, the most uncoordinated large research undertaking, has been very successful in developing new techniques and solving problems. They ask: “Should we spend long hours in coordinating meetings or should we get a good man and leave him alone?”
The ability of low and high temperatures to overcome endo- and paradormancy along with the possible mechanisms involved in these treatments for breaking apple (Malus domestica Borkh. `Anna') bud dormancy were studied. All these treatments induced budbreak in paradormant (in July) and endodormant (in October) buds. Cold and heat treatments increased ascorbic acid, the reduced the form of glutathione (GSH), total glutathione, total non-protein thiol and non-glutathione thiol, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased. The treatments also increased the ascorbic acid: dehydroascorbate and GSH: GSSG ratios and the activity of ascorbate-free radical reductase, ascorbate peroxidase, dehydroascorbate reductase, ascorbate oxidase, and glutathione reductase in the buds. These results indicate that budbreak induced by cold and heat treatments is associated with the removal of free radicals through activated peroxide-scavenging systems.
Bloom application of aminoethoxyvinylglycine (AVG) increased the fruit yields of ‘Ultra Red Delicious’ apple (Malus domestica Borkh.) trees. In one season, sprays of 50 ppm AVG were more effective in increasing yield than those of 500 ppm. In the second season, treatment with 150 and 225 ppm AVG was most effective. High levels of AVG (> 225 ppm) caused excessive fruit set and decreased fruit size. Ethylene evolution from developing fruits and fruiting spurs was decreased by AVG treatment.
A rapid sampling technique was developed to determine ethylene content of wood and buds of ‘Golden Delicious’ apple (Malus domestica Borkh.). The technique involves the use of a glass vial and 2 syringes per sample. One syringe was used to create a partial vacuum in a vial containing the sample tissue for a period of time, a second to remove a gas sample after the atmospheric pressure had returned to normal. On a n1/g basis, spur buds contained more ethylene than 1 or 2-year-old wood. Ethylene content of shoot bases remaining on the tree increased between 24 and 60 hours after pruning. Ethylene content of tissues sprayed with ethephon rose, then returned to normal after 9 days. The ethylene content of atmosphere in the Beltsville area fluctuated daily and should be considered in estimating absolute levels of ethylene generated by the tissue.