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George C. Martin

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George C. Martin

Abstract

‘Tan-ginbozu’ dwarf rice was responsive to root-applied gibberellins which had previously been separated by thin layer chromatography on glass fiber sheets. A 3-day test was less variable than 4, 5, 6 or 7-day tests. Seven replications enabled 50% differences in growth to be discernible with 95% confidence among 3 treatments; with 2 treatments, 50% differences in growth were discernible with 4 replications.

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George C. Martin

Abstract

None of the physiological events in plant growth and development is truly independent. Photosynthesis, flowering, and mineral transport are sharply focused areas of research; yet these phenomena are not separable from other metabolic events in the plant. This feature of interdependence may be called correlations (26) or growth correlations (49, 50). The control exerted by the growth zone emanates from a meristem; these meristems include the root or shoot apex, cambium, flowers, fruit, pollen on stigma, and the ovule or seed in a fruit.

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George C. Martin

Abstract

Historians tend to find what they are looking for. My bias in developing historical aspects of Growth Regulators (GR) in Pomology has been positive, as I believe that control of plant growth will eventually be possible. The thought processes and actions taken by individuals who led the way to eventual use of GR are difficult to access. Perhaps the beginnings were initiated by those who had the time to observe plant growth and write down what they saw. To credit any one individual would be of doubtful accuracy. Historically, the one who accumulates fame for a breakthrough put the finishing touches on an idea which had evolved over a long period of time.

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George C. Martin and C. Nishijima

Abstract

Large differences in abscisic acid (ABA) concentrations were found among persisting fruit of ‘Winter Nelis’, seeded ‘Bartlett’ and parthenocarpic ‘Bartlett’ pear (Pyrus communis L.) even though fruit set and fruit growth rates were similar. Concentration of ABA was positively correlated with rate of fruit and seed growth in these 3 pear types. The concentration of ABA was greater in the seed than in fruit flesh, and in the integuments plus endosperm than in the embryo.

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George C. Martin and C. Nishijima

Abstract

Analysis for hormones in plant material received impetus from the early studies of Went (4). Since that time, scientists have used living plant materials to estimate the presence of specific hormones. Among the advantages of the bioassay are sensitivity to the nanogram and in some cases, picogram range, ease of use, functionality with high levels of contaminants, and low cost of operation. The disadvantages include lack of specificity, variable response, and, in most instances, the need to use a species foreign to the one under examination.

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Kiyoshi Banno and George C. Martin

Olive fruit harvest by mechanical shaking continues to be limited by poor fruit removal - less than 60% removal for most varieties. Whereas foliar spray of ethylene releasing compounds such as ethephon increases fruit removal percent, excessive leaf loss following treatment precludes commercial acceptance of the treatment. A classic case of serendipity has led to the testing of phosphorus as an olive fruit loosening agent. Na2 HPO4 at 25 mM applied via the cut stem of explants leads to massive leaf and fruit abscission. When the P source is applied at 100 mM foliar spray, fruit removal is accomplished with minimal leaf loss. Results of this investigation will cover P source, concentration, genera with abscission response and some indication of mechanism of action.

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Hisashi Yamada and George C. Martin

Adding Al2O3 to 8-hydroxyquinoline citrate (8-HQC) solution did not alter the sensitivity of the leaf abscission zone to external ethylene. Exogenous ethylene at 791 nl·liter-1 for 72 to 120 hours and at 193 nl·liter-1 for 120 hours induced leaf abscission, whereas no leaf abscission occurred at 47 nl·liter-1 for 72 to 120 hours. Ethylene at 791 nl·liter-1 for 72 to 120 hours increased ethylene evolution, but the amount of ethylene evolved from the explants does not seem to be enough to induce leaf abscission. Three different ethylene inhibitors—aminooxyacetic acid (AOA), CoCl2, and aminoethoxyvinylglycine (AVG)—were used to determine whether P-induced leaf abscission was mediated through elevated ethylene evolution. Although AOA and CoCl2 failed to inhibit ethylene evolution from the explants stem-fed with NaH2PO4, AVG inhibited ethylene evolution. Each inhibitor, except 5 mm CoCl2, promoted leaf abscission when administered alone or with P. Our results reveal that P-induced olive leaf abscission may occur without elevated ethylene evolution. At 40 or 75 mm NaH2PO4, abscission did not occur until explants were removed from N2 and placed in ambient air.

Free access

Hisashi Yamada and George C. Martin

The addition of Al2O3 to 8-hydroxyquinoline citrate (8-HQC) solution did not alter the sensitivity of the leaf abscission zone to external ethylene treatment. Exogenous ethylene at 791 nl·l-1 for 72 to 120h and at 193 nl·l-1 for 120h induced leaf abscission whereas at 47 nl·l-1 for 72 to 120h no leaf abscission occurred. Ethylene treatment at 791 nl·l-1 for 72 to 120h increased ethylene evolution, but the amount of ethylene evolved from the explants does not seem to be enough for leaf abscission induction. Three different ethylene inhibitors, aminooxyacetic acid (AOA), CoCl2 and am inoethoxyvinylglycine (AVG), were used to determine whether phosphorus-induced leaf abscission was mediated through elevated ethylene evolution. Although AOA and CoCl2 failed to inhibit ethylene evolution from the explants stem-fed with NaH2P O4, AVG inhibited ethylene evolution. Each of the inhibitors except for 5 mM CoCl2 promoted leaf abscission when administered alone or with phosphorus. Our results reveal that phosphorus induced olive leaf abscission occurs without elevated ethylene evolution, but that oxygen is required.

Open access

George C. Martin

Abstract

Spray application of 2-chloroethylphosphonic acid (ethephon) to walnut trees caused dehiscence of hulls and enabled complete nut removal with a single mechanical shaking operation as much as 3 weeks earlier than normal. Walnuts were hullable and the quality was generally superior to that of the controls. In some instances considerable leaf fall resulted from the treatment.