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- Author or Editor: A. H. Thompson x
A greenhouse solution culture experiment was conducted to study the interactions of Ca, K and Mn supply on the concentration of 7 elements in bark tissues of ‘Delicious’ apple (Malus domestica Borkh) trees as related to internal bark necrosis (IBN). Under a regime of low Ca and high Mn, IBN symptoms developed late in the second growing season on the scion barks but not on the rootstock bark. Both the degree of severity and the incidence of the disorder increased with increasing K levels. Low Ca and high Mn concentrations in the barks are apparently necessary for the development of IBN, and under these conditions K affects the degree of severity. It is suggested that the higher K concentrations enhanced Mn toxicity by lowering the threshold for Mn-induced IBN, while Ca responded as a detoxifying agent. Low concentrations of B and P may contribute to IBN development, while Mg and Fe were not related to symptom development.
Naphthaleneacetic acid (NAA) and 1-naphthyl N-methyl carbamate (carbaryl) applied separately in both dilute and concentrated sprays significantly increased fruit size; however, when butanedioic mono-2,2-dimethylhydrazide (daminozide) was added, fruit size remained about the same as on unsprayed check trees. Crop load was not significantly affected by any of these treatments. Dilute and concentrated sprays of carbaryl produced more return bloom than did NAA. The most effective treatments were combinations of NAA and carbaryl, either dilute or concentrated. Combining first-cover pesticides [azinphosmethyl (guthion) and cis-N-(trichloromethyl)thio)-4-cy-clonexane-l,2-dicarboximide (captan)] with NAA, and captan with carbaryl, produced satisfactory thinning.
Three years’ investigations of ethephon sprays for thinning of ‘Redskin’ and ‘Redhaven’ cvs. are summarized. In screening, thinning without foliage injury was achieved up to about 3 weeks after full bloom at concn up to 300 ppm. Field experiments tended to confirm screening results. Within timing used, satisfactory thinning was accomplished most often during blossoming. Foliage injury generally increased as application was delayed and as concn increased. Fruit size at harvest was increased more by blossom treatments than later application. Fruit abscission occurred quickly after spraying. Ethephon is most promising as a peach thinning chemical, but time-dosage curves within acceptable injury Emits are not yet established.
`Gasaway' hazelnut (Corylus avellana L.) is highly resistant to eastern filbert blight caused by Anisogramma anomala (Peck) E. Muller. Progeny produced from controlled crosses of `Gasaway' with five susceptible genotypes and open pollination in a `DuChilly' orchard were planted in a diseased orchard and rated for symptom expression for 9 to 10 years. All progeny were found to segregate 50% resistant: 50% susceptible, indicating that `Gasaway' is heterozygous for a single dominant resistance gene.
N and P fertilization at planting increased plant height in the first growing season of ‘Golden Delicious’ apple trees (Malus domestica Borkh.) on Mailing (M) 26 rootstocks. P fertilizer stimulated lateral bud break and, at 0.023 kg P, resulting in an increase in trunk caliper. When P was combined with 2,000 ppm butanedioic acid mono-(2,2-dimethylhydrazide) (daminozide), no trunk response resulted. The greatest number of flower clusters and fruits developed as a result of 0.046 kg P in combination with daminozide.
Sevin was used in thinning sprays in dilute—1x—and concentrate form—ranging from 3X to 33X —over a 4-year period on mature ‘Rome Beauty’ apple trees. Although treatments were not the same in each year, all sprays applied significantly thinned in 3 out of 4 years. There was some evidence that concentrate sprays thinned less than dilute sprays, but usually not significantly so. When using 33X concentrates, significant thinning was achieved in 1 year when Sevin was used at full strength—33 lb./100 gal. Approximately the same degree of thinning was obtained when the rate was reduced by one-half. Adding pesticides commonly used in petal-fall sprays to Sevin—all concentrated to the same extent—did not alter significantly the thinning obtained with Sevin alone.
Results on ‘Jonathan’ apples in a 1-year experiment revealed significant thinning with NAD and Sevin in a dilute spray, as well as Sevin at 3X and 6X concentrates. In a 1-year experiment on ‘Golden Delicious’, NAA thinned significantly as a dilute spray, and at 3X and 6X concentrates. The dilute spray was more effective.
Lesquerella fendleri (Gray) Wats. (Brassicaceae) is a potential oilseed crop with many commercial applications, primarily as lubricant additives, but also in resins, waxes, plastics, and cosmetics. This species is native to the southwestern United States where new populations have been collected over the past 2 years to increase germplasm diversity for plant breeding. Some of these new accessions were evaluated and seeds increased at Phoenix, Ariz., over the 1994–95 season. Measurements of stand establishment; plant height and width; leaf, shoot, and flower characteristics; and growth habit were taken over the season. Plants were also examined for autofertility and male sterility. Seed-oil characteristics, seed size and yield, glucosinalate content, and seedcoat gum content will be measured at harvest. Plant descriptors for Lesquerella have been developed as a result of these measurements. Following seed increase, germplasm will be entered into the National Plant Germplasm System. This information will be useful in determining the most promising material for plant breeding.
‘Jersey’ blueberry plants were greenhouse-grown through 1 season with treatments consisting of a factorial combination of 4 soil factors: inoculation with a mycorrhiza-forming fungus; high or low nutrient regime; with or without leachate from a native blueberry soil; and soil porosities corresponding to a clayey, silty, or sandy, and a native blueberry soil, Berryland, as a standard comparison. Although very low in nutrient elements, Berryland soil or its leachate significantly increased plant growth. There was no significant effect on growth from mycorrhizal inoculation at either high or low nutrient levels and only a slight effect from varying the soil free-pore space.
Seedlings of highbush blueberry (Vaccinium corymbosum L.) subjected to 3 fungal treatments and 2 soil pH levels (4.2 and limed to 6.0) displayed no significant treatment interaction in respect to growth, mycorrhizal infection intensity, or nutrient uptake. Among the fungal treatments, there were differences in nutrient uptake and infection intensity, but no difference in total linear stem growth or number of shoots. Lower soil pH resulted in significantly greater stem growth and number of shoots; however, intensity of infection was not significantly different compared to the high pH soil.
The pressure microprobe has been used to measure cell turgor and, in addition, to sample vacuolar tissues. In carrot, a rapid initial loss of tissue firmness (instron technique) occurred when the tissue was heater (cooked), and this could be entirely attributed to a loss in cell turgor. Turgor was well-correlated to firmness over the range of turgor measurements (0–0.8 MPa). In cherry and other fruits, turgor is typically 1 to 2 orders of magnitude lower than that expected based on cell osmotic potential, indicating the presence of apoplastic solutes. Cherry fruit firmness and cell turgor were well-correlated during the first 2 h of hydration at 20C, but, as fruit began to crack, tissue decreased, whereas turgor continued to increase.