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Abstract
Ten day-old seedling pecans (Carya illinoensis (Wang.) K. Koch) grown in square plastic pots, speedling containers and styrene cylinders were treated with 1000 mg/liter 6-benzyIamino-purine (BA) and 5000 mg/liter gibberellic acid (GA3) singly and in combination. GA3 at 5000 mg/liter promoted stem diameter enlargement of seedlings grown in cylinders and pots but had no effect on stems of speedling-grown seedlings. BA and container design had no influence on stem diameter. “Air-pruning” of roots which occurred in speedling-grown seedlings produced a compact, fibrous root system. Stem diameter and height were not significantly reduced by root “air-pruning.” GA3 significantly reduced root dry weight of seedlings grown in cylinders.
A procedure to determined selection of sweetpotato (Ipomoea batatas L. Lam.) genotypes tolerant to chilling injury was initiated by crossing two resistance lines and two susceptible lines. Experimental design on the F1 progeny was a completely randomized design (CRD) with two groups, tolerant and sensitive genotypes, and 90 lines in each group. Four plants per lines were selected and each plant represented a replication. The rating of plants according to the degree of chilling injury was recorded at 36 h after chilling temperature of 5 °C with 85% relative humidity. Significance of the analysis was based on the number of plants tolerant to chilling injury from both the resistant and the sensitive groups. Results from the statistical analysis based on visual rating of the F1 progeny plants for 36 h, indicated that higher populations of resistant plants could be produced when two resistant lines were crossed in a control pollination process. Evaluations to be continued are chlorophyll fluorescence, leakage of cell content, structural changes of the cell, and peroxidase content, before and after chilling stress. These assays will be used to further determine the similarities among the chilling-tolerant genotypes. Findings will aid in elucidating mechanism of chilling injury in fruit and vegetables.
A field experiment was established in 1980 to determine the effect of different combined levels of ammonium nitrat e (196-695 kg/ha), potassium chloride (56-196 kg/ha) and magnesium oxide (123-437 kg/ha) on `Noble' and `Magnolia' muscadine cultivars (Vitis rotundifolia Mich.). NH4NO3 rates of 196 to 695 kg/ha did not produce significant differences in yields and pruning weights (P=0.05). 'Noble' produced similar yields at the highest and lowest N rates, with equivalent rates of K and Mg. KCl at 84 kg/ha and MgO at 123 kg/ha appeared to be adequate. Foliar levels of K, Mg and Zn were significantly different between treatments, but P, Ca and Fe were not (P=0.05). High levels of foliar K and Mg were associated with high treatment levels of K and Mg.
Abstract
Six stages of floral development were identified and related to air temperature in Carya illinoensis (Wang.) K. Koch, cv. Western. Initiation (the first microscopically visible evidence of floral primordia) was detected on April 4, 1973, after an accumulation of 537 heat units. On April 10 a total of 598 heat units were accumulated when 93% of the buds sampled had initiated pistillate flowers. Floral development occurred normally, uniformly, and in concert with the heat units accumulated.
Abstract
The ethylene inhibitors L-2-amino-4-(2-amino-ethoxy)-trans-3-butenoic acid hydrochloride (AVG) and L-2-amino-4-methoxy-trans-3-butenoic acid (MVG) significantly reduced the number of reproductive shoots and percent open flowers of Nemesia strumosa low. But not of Schizanthus × wisetonensis Benth. 7 days after treatment. MVG and AVG were most effective at 26.2 and 39.3 ppm, respectively. Photoperiod did not influence flowering of either species, but vegetative senescence of Schizanthus was influenced by photoperiod.
The objective of this study was to relate the lethal freezing temperatures of St. Augustinegrass [Stenotaphrum secundatum (Walt.) Kuntze] genotypes, as measured by differential thermal analysis (DTA), to winter survival observed in the field. DTA-predicted lethal temperatures of 14 St. Augustinegrass genotypes ranged from –7.7 to –4.7C. Regression of field winter survival vs. DTA-predicted lethal temperatures resulted in an r 2 = 0.57 for one field trial that evaluated cultivars with a relatively narrow range of expected freezing tolerance. In a second study evaluating cultivars with a greater range of freezing tolerance, r 2 was 0.92 when winter survival was regressed on DTA-predicted lethal temperatures. DTA was successful in measuring freezing avoidance of St. Augustinegrass cultivars.