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Abstract
Peach [Prunus persica (L.) Batsch] trees were developed into a Y shape without trellis support in orchards with tree densities from 629-897 trees/ha for complete mechanization. Considerable hand pruning was used the 1st year to train the Yโs, but nearly all subsequent pruning was done with a mowing machine sickle bar. Limited experience indicated that the Y shaped tree is well suited for an over-the-row machine that will operate a pruner, sprayer, and continuously moving harvester. Fresh marketable yields of โCoronetโ from 1977 through 1981 for the wall ranged from 6.7โ22.8 MT/ha and, for the Yโs, ranged from 5.7โ25.2 compared to 5.4โ15.7 MT/ha for the standard trees. The Y shaped trees and tree walls were more productive than standard trees through the 5th year.
Abstract
Peach tree short life (PTSL) is a serious problem in the southeastern United States. Time of pruning (1, 2, 6), low temperatures (5), rootstock (9), inadequate liming (7), cultural practice (8), fumigation (8), orchard site (2), and the ring nematode, Criconemella xenoplax (Raski) Luc & Raski (8, 4) have been associated with PTSL. An interaction of bacterial canker and time of pruning has been demonstrated (2) and other interactions have been suspected. Certain factors (e.g., over-cropping and drought) might stress the tree and reduce its vitality, thus increasing its susceptibility to bacterial canker or other diseases and/or freeze injury.
Peach (Prunus persica, L. Batsch) cultivars vary in the percent of marketable stage fruit from a once-over harvest. Maturity stages are difficult to separate. The difficulty might be related to non-uniform ripening characteristics of the fruit. A method was developed to estimate the variability in maturity at 16 coordinates around the peach. Peaches were sampled at 5 maturity stages: 1) about 1/2 final-swell size; 2) 90% final-swell size; 3) and 4) marketable, and 5) soft ripe. Stages were separated by color chips #1 and #2, #3 and #5 (marketable), or #6. Pared flesh firmness was measured with a modified penetrometer plunger (4.47mm diameter tip 11mm long). Force (F) ranged from about 3 to 45 N. Soluble solids (SS) ranged from 10 to 13% from a 1cm3 cylinder adjacent to the puncture made by the penetrometer. Force and SS from five replications of 2 cultivars indicate that the apex and cheeks are the firmest and highest in SS for most stages tested. Reported correlations of F on the cheek with the yellow ground color or sweetness within marketable fruits are negative. However, correlations in this experiment ranged from R2 = 0 to 0.18 for the green to ripe stages.
Cultivars of fresh market peaches (Prunus persica, L. Batsch) vary in the duration for maximum yields in the shipping stage (firm ripe) from once-over harvests. A cultivar having many firm ripe fruit with few green and over ripe at a given time has a narrow maturity range. It can be picked fewer times, facilitate mechanical once-over harvests and reduce spray costs. Fruit were harvested from small trees or scaffold branches of large trees at 2- to 3-day intervals as once-over harvests on 4 dates to estimate maturity range and duration of the maximum firm ripe fruit. Fruit of 3 cultivars were graded by color into maturity stages: 1) green, 2) firm ripe, and 3) over ripe. `Loring' had 82% firm ripe sorted in the 1st 3 harvests in 1987 and 1988. `Redskin' had 83% firm ripe in the 2nd and 3rd harvests in 1987. `Redglobe' had 85% marketable in the 2nd and dropped to 75% in the 3rd harvest in 1987. `Redhaven' had about 80% firm ripe in the 1st 3 harvests in 1988. Results indicate that the duration of narrow maturity ranges of `Loring' and `Redhaven' would permit them to be harvested over about 5 days with high yieids in the firm-ripe stage.
Variability in maturity within a peach (Prunus persica, L. Batsch) fruit was estimated by measurements of force and the soluble solids concentration (SSC) at 16 coordinates around the peach at five maturity stages: 1) about one-half final swell (immature); 2) 85% final swell (green); 3) firm-ripe and similar to chip #3 of the Clemson Univ. system; 4) firm-ripe and similar to chip #5; and 5) tree-ripe. Firm-ripe 3 and 4 stages were firm enough to ship, but the tree-ripe stage was too soft. Firmness measured with a 4.7-mm-diameter penetrometer tip from two cultivars indicates a strong trend for the peach tip and cheeks to be firmer than tissue at other coordinates. Coordinates at the equator and around the stem end are generally firmer than coordinates at lat. 45ยฐN, particularly in stages 3, 4, and 5. The SSC in juice from a cylinder of fruit adjacent to the puncture was higher at long. 90ยฐE-W than at the sutures and higher at lat. 0ยฐ than at 70ยฐS. Variance increased for force and decreased for SSC between maturity stages to the firm-ripe stage. The coordinate technique might be used to characterize and select cultivars that would be most suitable for once-over harvests.
Abstract
Peach (Prunus persica (L.) Batsch) seedlings were grown in nutrient solutions containing 0, 222, 666, 1333 or 2000 ฮผM Al. Diffusive resistance (DR) increased as Al concentrations increased and were significantly higher at 2000 ฮผM Al than at lower concentrations. Stomatal apertures were larger on seedlings grown in 666 ฮผM than those in 222 or 1333, those of the check were smaller, and those in 2000 ฮผM Al were the smallest. Root volume decreased as Al concentrations increased. Changes in DR appeared to be more closely related to root volume than to stomatal aperture or density.
Abstract
Seedlings of โBabygold 5โ peach [Prunus persica (L.) Batsch] were grown for 50 days in nutrient solutions with 0.4, 21, 42, 125, 250, 500 ฮผm Mg. Magnesium deficiency symptoms were observed 19 days after initiation of the Mg treatments in the seedlings in 0.4 ฮผm Mg solutions. The relative growth rate was significantly increased for the first increment of Mg concentration with no further increases at higher Mg concentrations. Increasing Mg in the nutrient solution significantly increased Mg concentration in the leaves, stems, and roots, but Mg tissue concentration decreased at all levels of Mg in the nutrient solution as physiological age increased. Visible Mg deficiency symptoms were observed on mature leaves at the 125 ฮผm Mg treatment, but when the Mg concentration exceeded 250 ฮผm, Mg concentration in mature leaves was increased above the threshold for appearance of Mg deficiency symptoms. No Mg deficiencies were observed on โBabygold 5โ seedlings when the Mg concentrations in the leaves exceeded 2000 ฮผg/g dry weight and Mg uptake rate was 2.5 ฮผmoles/g fresh wt./day.
Abstract
Peach [Prunus persica (L.) Batsch] seedlings of โSiberian Cโ, โTzim Pee Taoโ, NA 8, and 152A1โ2 were grown for 64 days in nutrient solutions with constant N concentration, but the ratio of NO3 to NH4 in the nutrient solution varied from 100:0 to 0:100. The greatest growth occurred when the NO3:NH4 treatment was 50:50 or 25:75. The poorest growth occurred when NO3 was the sole N source in the nutrient solution. Significant interaction of nutrient concentrations occurred with the different rootstock and N ratios in all tissues studied. The N concentration in leaves and roots was highest in seedlings grown in N treatments of 100:0 or 75:25. The concentrations of P, Ca, and Mg in the leaves, stems, and roots of all cultivars decreased with each increment increase in the NH4 concentration in the nutrient solution. The relative growth rate and N uptake rate of all seedlings increased with high NH4 concentrations. The uptake rates of P, K, Ca, and Mg were highest for NO3:NH4 treatments of 50:50 or 25:75. Chlorosis developed on margins of leaves mid-way on the main stem on all seedlings with NO3:NH4 treatments 50:50, 25:75 and 0:100. The disorder occurred in the mature leaves of all cultivars but did not affect expanding leaves.
Abstract
Seedlings of โLovellโ and โElbertaโ peach [Prunus persica (L.) Batsch] were grown in the greenhouse for 29 or 50 days in nutrient solutions containing 8, 16, 33, 66, 132, 264, or 660 ยตM Ca at pH 4.5. Relative growth rate was unaffected by Ca concentrations. Calcium concentration in the stems was increased from 700 to 4330 ยตg/g dry weight and in the roots from 348 to 1787 ยตg/g dry weight by Ca treatments for the 29 days of growth. No Ca deficiency symptoms were observed on the seedlings when the Ca concentration in the leaves exceeded 2300 ยตg/g dry weight. The Ca uptake rates during the 29 days of growth for โLovellโ increased from 0.46 to 3.77 and for โElbertaโ from 0.44 to 2.84 ยตmoles/g fresh-weight-root/day. After 50 days of growth, Ca uptake rates increased for โLovellโ from 0.58 to 3.51 and for โElbertaโ from 0.52 to 3.02 ยตmoles/g fresh-weight-root/day. Calcium accumulated in stems when Ca concentration in the nutrient solution exceeded 264 ยตm Ca with no change in total Ca content in the roots. The K and P uptake rates were increased by higher Ca treatments but the Mn uptake rate was decreased when the Ca concentration in nutrient solution was greater than 66 ยตm.
Abstract
Total nutrient content, uptake rates, and distribution were determined for seedlings of peach [Prunus persica (L.) Batsch] grown in nutrient solutions containing 0, 222, 666, and 2000 ยต m Al. Generally, total nutrient content decreased in the peach seedling organs as Al concentration increased. The responses obtained with increased Al concentration were linear with some nutrients and curvilinear with others and varied with plant organ. As Al concentration increased, the uptake rates for P, Ca, Mg, Zn, and Mn decreased but those for K and Fe increased. Aluminum did not alter the translocation of most nutrients; however, a greater percentage of the absorbed Ca accumulated in the leaves than in the roots or stems. Thus, aluminum toxicity in peaches may be related to a reduction in Ca uptake rate and not to inhibition in translocation of Ca.