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- Author or Editor: George C. Martin x
Abstract
Foliar sprays of 2-chloroethylphosphonic acid (ethephon) at petal fall or when the ovules had grown to 4 or 9 mm resulted in an acceptable level of thinning on ‘Johnson’ and ‘Halford’ peach. Thinning of ‘Fay Elberta’ with ethephon occurred at the 5- to 9-mm ovule length. Foliar sprays of 1,1,5,5-tetramethyl-3-dimethylaminodithiobiuret (ER-3952) effectively thinned ‘Johnson’ and ‘Halford’ at the 4- to 9-mm ovule length but gave poor results with ‘Fay Elberta’.
Abstract
Sensitive analytical techniques such as gas chromatography or combined gas chromatography-mass spectrometry, detect not only plant hormones, but chemical contaminants as well. Thorough cleaning of solvents and chromatographic materials used for extracting plants as well as identification of the contaminants present will assist in resolving the contaminants from hormones present in the same extract.
Abstract
In the article “Endo-, Para-, and Ecodormancy: Physiological Terminology and Classification for Dormancy Research” by Gregory A. Lang, Jack D. Early, George C. Martin, and Rebecca L. Darnell (HortScience 22:371–377, June 1987), in the second column of Table 5 under part III-B (paradormancy), the term “Cryogenic endodormancy” should be changed to “Cryogenic paradormancy”.
Abstract
Plant dormancy has a major impact on the cultivation of plants, influencing such processes as seed germination, flowering, and vegetative growth. The diversity of plant tissues that exhibit, or contribute to the manifestation of, dormancy is great, and there appear to be numerous mechanisms of dormancy induction or release. This complexity was discussed by Romberger (55) nearly 25 years ago. Yet his analysis of the unresolved challenges in dormancy research is still valid today, for the overall understanding of dormancy is limited. This lack of understanding may be due, in part, to the abundance of terminology that has arisen without a nomenclatural framework in which to classify and relate the events being described.
Abstract
Germination of stone fruit seeds is accelerated at an elevated percentage if the stony endocarp (pit) is removed prior to planting. Stone fruit breeders and those who screen seed populations usually remove pits with bench vice jaws that manually compress pits either end-to-end or edge-to-edge to affect seed release. The vice was effective but production was low and seasonal production was limited. Consequently, efforts were initiated to find means to alleviate the problem of low seed release productivity while maintaining the effectiveness of the vise.
Ethephon reduces olive fruit removal force but also results in leaf loss when used as a harvest fruit loosening agent and in reduction of flower production in the subsequent year. Phosphorus (P) has been implicated in the fruit loosening process. Nuclear magnetic resonance analyses indicate that P accumulates rapidly in olive leaf explant abscission zones. P also causes ethylene evolution prior to abscission; this effect appears to be direct. In combination with AOA an ethylene synthesis inhibitor, P accelerates `Manzanillo' leaf explants abscission, inducing significant abscission 3 days after treatment. These results will assist in development of a P use strategy that leads to fruit but not leaf abscission.
When continuously stem-fed with 75 mm NaH2PO4, `Manzanillo' olive explants showed significant leaf abscission after 48 hours; by that time 1.042 mg·g-1 fresh weight P had accumulated in the abscission zone (AZ). The potential contribution of ethylene to phosphate-enhanced abscission was investigated using aminooxyacetic acid (AOA), an ethylene-synthesis inhibitor, and by measuring ethylene evolution in phosphate-treated explants. In combination with NaH2PO4, AOA did not affect leaf abscission. Though ethylene evolution from explants increased as leaf abscission was initiated, it was about two orders of magnitude less than the concentration necessary to induce leaf abscission as judged by exogenous treatments. Based on leaf-abscission kinetics, we have concluded that the mechanism of P-induced abscission is independent of gross measurement of evolved ethylene, but we cannot rule out ethylene confined to the AZ itself. When evaluated for P-induced leaf abscission, leaves of `Manzanillo' and `Sevillano' abscised earlier than `Ascolano' and `Mission'.
Abstract
Foliar sprays of (2-chloroethyl)phosphonic acid (ethephon) were applied at 50, 100, and 150 ppm to French prune trees at 50% petal fall and when seed length was 8.3 to 9.4 mm. All concentrations thinned fruits within 3 to 4 weeks after treatment. The treatments increased soluble solids and fruit size, and in some instances decreased dry tonnage. Return bloom the following year was greater on treated trees than on controls. Also, fall coloration patterns appeared earlier on the treated trees. No phytotoxic effects from the treatments were evident on the fruits.
A long-term horticultural experiment was conducted at two geographically distinct sites in southern Missouri in 2011–15 to study the response of American elderberry [Sambucus nigra (L.) subsp. canadensis (L.) Bolli] to various soil nitrogen (N) fertilizer levels. Three commercially available elderberry cultivars (‘Adams II’, ‘Bob Gordon’, and ‘Wyldewood’) were used. The three cultivars were each assigned to 16 of 48 four-plant plots in a completely randomized manner at each site. Four replications of four N fertilizer treatments (0, 56, 112, 169 kg⋅ha−1 N) were randomly assigned to each cultivar’s plots and applied for 4 years (2012–15). Fruit yields, plant growth, phenology, and pest incidence were determined each year. Fruit quality was assessed by analyzing basic juice characteristics as well as organic acids, carbohydrates, anthocyanins, and polyphenols from 2012–14 samples. Leaf tissue analysis determined the plants’ mineral contents in 2012–14. Most factors evaluated were significantly affected by site, year, and cultivar, whereas the effects of N fertilizer treatment were less definitive. Fruit yields and plant growth increased with increasing N levels. For example, plants fertilized with 0, 56, 112, and 169 kg⋅ha−1 N produced 123, 137, 155, and 161 fruiting cymes per plot (5.8 m2), respectively. The eriophyid mite incidence was higher on fertilized plants, but other pests were not influenced by the N treatment. Basic fruit juice characteristics (soluble solids, pH, titratable acidity, polyphenols) were not influenced by the N treatment, whereas total anthocyanins were statistically higher in unfertilized plants. Levels of organic acids and carbohydrates in juice varied statistically among N treatments, but patterns were difficult to discern. Leaf N concentrations were correlated with N fertilizer levels—2.75% N with the highest fertilizer level compared with 2.55% N in unfertilized plants. Leaf levels of most other macronutrients varied, but consistent patterns did not emerge, and none of the micronutrients was different among N treatments. Although elderberry plants responded positively to increased N fertilizer levels in terms of plant growth and fruit yield, genetics (cultivar) and environment (site, year) were more influential on most other experimental factors evaluated.