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Abstract
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.
Abstract
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?”
Abstract
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.
Abstract
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.
The activity of ascorbic acid oxidase (AAO) was studied in apple (Malus domestica Borkh.) buds during dormancy and thidiazuron-induced budbreak. In dormant buds, activity of AAO was low compared with buds that were treated with thidiazuron and had resumed growth. An increase in AAO activity began at the time of metabolic transition from dormancy to budbreak. The highest level of activity was reached 10 days after thidiazuron induction during the expansion growth phase. In vitro AAO activity of apple bud extract was increased by addition of Cu (CuSO) and inhibited by Cu-chelating agents, diethyldithiocarbamate (DDC), sodium azide (NaN), and 8-hydroxyquinoiine (8-OH-Q). In vivo treatment of apple buds with Cu-chelating agents inhibited AAO activity and bud growth but not budbreak. Chemical name used: N- phenyl -N' -1,2,3-thidiazol-5-ylurea (thidiazuron).