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Two experiments were conducted to determine the effects of leaf age and shading on the phenolic content and composition of apple foliage. In the first study, it was determined that the phenolic content of `Liberty', at increasing leaf developmental stages, was leaf age—dependent. Early during leaf development, there was an increase in the phloridzin (the primary glycoside identified) and in total phenolics, reaching a maximum when the leaf is 6 days from 20-mm blade length. After this stage, the phenolic content decreased with increasing leaf age. In the second study, the leaves of two cultivars, `Liberty' and `Starkspur Law Rome', were tagged weekly when the leaf was two-thirds unfolded. Three weeks after budbreak, the trees were placed under three shade cloth treatments (0%, 60%, and 90% shade). After 4 weeks under the shade treatments, the tagged leaves were collected to determine their phenolic content. Shade significantly affected the foliar phenolic content. Leaves in 0% shade had the highest phenolic content, whereas the lowest content was found in leaves exposed to 90% shade. There was a significant leaf age × shade interaction. The phenolic content decreased with increasing leaf age except for those leaves whose development occurred before the experiment was started. The results indicate that light and leaf developmental stage are important factors in determining the phenolic content of apple leaves, but shading appears to have a stronger influence than leaf developmental stage. E-mail mgarcia@zoo.uvm.edu; phone (802) 656-2824.
Two experiments were conducted to determine the effects of leaf age and shading on the phenolic content and composition of apple foliage. In the first study, it was determined that the phenolic content of `Liberty', at increasing leaf developmental stages, was leaf age—dependent. Early during leaf development, there was an increase in the phloridzin (the primary glycoside identified) and in total phenolics, reaching a maximum when the leaf is 6 days from 20-mm blade length. After this stage, the phenolic content decreased with increasing leaf age. In the second study, the leaves of two cultivars, `Liberty' and `Starkspur Law Rome', were tagged weekly when the leaf was two-thirds unfolded. Three weeks after budbreak, the trees were placed under three shade cloth treatments (0%, 60%, and 90% shade). After 4 weeks under the shade treatments, the tagged leaves were collected to determine their phenolic content. Shade significantly affected the foliar phenolic content. Leaves in 0% shade had the highest phenolic content, whereas the lowest content was found in leaves exposed to 90% shade. There was a significant leaf age × shade interaction. The phenolic content decreased with increasing leaf age except for those leaves whose development occurred before the experiment was started. The results indicate that light and leaf developmental stage are important factors in determining the phenolic content of apple leaves, but shading appears to have a stronger influence than leaf developmental stage. E-mail mgarcia@zoo.uvm.edu; phone (802) 656-2824.
The effects of shading and leaf age on the production of foliar phenolics of two apple (Malus domestica Borkh.) cultivars, `Liberty' and `Red Rome Beauty', were studied. Potted trees were grown outdoors and their leaves tagged weekly when they reached 20 mm in length. This process continued for the duration of the experiment. At 3 weeks from budbreak, the trees were placed in three shade treatments: 0% shade (control), 60% shade, and 90% shade. After 5 weeks, the leaves were collected for phenolic assay. Specific leaf weight (SLW) was determined from the leaf below the tagged leaf. Shade significantly affected the total phenolic content. Leaves in 0% shade had the highest levels of total phenolics. The phenolic content decreased with increasing shade, with trees in 90% shade having a 72% reduction in total phenolics. There was a significant shade by leaf age interaction. There was a decrease in total phenolic content with increasing leaf age except for those leaves whose development occurred before the experiment was started. The 1-week-old leaf had the highest phenolic content, while 4-week-old leaf had the lowest amount. The 5- and 6-week-old leaves that had been tagged prior to the onset of the shade treatments has similar phenolic content in all treatment. SLW significantly decreased with increasing shade and increased with leaf age. Results of this study indicate that light and leaf developmental stage are important factors in the total foliar phenolic content, but, once phenolics are synthesized, shading does not affect their content.
The level of dihydroxyphenolics as influenced by cultivar and leaf phenology was determined for 10 apple cultivars. Newly unfolding leaves were tagged weekly. Once per month, the leaves were collected and analyzed to determine their phenolic content. Replicated collections were made at three times during the summer. Diphenyl boric acid ethanol was the reagent used in this spectrophotometric technique. The phenolic content changed throughout the season. However, no trend was observed for phenolic content variation with leaf age. Each cultivar varied independently in phenolic content with leaf phenology. There were variations in the phenolic content associated with cultivar. Possible hypotheses as to factors affecting the production of phenolics in apple are discussed.
Abstract
Trees of Malus domestica (Borkh.) ‘Miller Sturdeespur’ were hand thinned to achieve light, medium, and heavy fruit loads. A heavy European red mite (ERM), Panonychus ulmi (Koch), infestation was encouraged by mite seeding and predator elimination in half the trees for each fruit load. The effect of these treatments were determined on fruit number, number and percentage of drops, fruit size, color, soluble solids, titratable acidity, pH, firmness, and percentage of foliar concentration for 5 macronutrients. Mite feeding increased the percentage of drop and reduced red pigmentation, soluble solids, and leaf phosphorus and calcium. Deleterious effects of mite feeding increased with increasing fruit load. With light fruit loads, heavy mite feeding had a negligible effect on fruit quality.
Ethrel sprays were applied at 50 or 100 ppm at approximately 40%, 70% leaf fall (10/16/89 or 10/24/89, respectively) or at both times on `Redhaven' and `Allgold' peaches. Bud hardiness was determined biweekly by differential thermal analysis (DTA). Stage and percentage of bloom open during the bloom period were subjectively estimated.
Spraying trees with 100ppm Ethrel at 50% leaf fall significantly increased bud hardiness at mid-winter compared to other treatments. After a mid-winter freeze (-21.7 C on 12/21/89), there was no significant difference between % bud survival of any treatments. But, trees treated with 50 or 100ppm Ethrel had 10-20% better bud survival than other treatments. Buds of the 2 cultivars had statistically similar hardiness although DTA analysis indicated that Redhaven had a .5-.8 C lower freezing point than Allgold in mid winter. This trend was reversed close to bloom with Allgold having .7 C lower freezing point than Redhaven. The time of full bloom was significantly delayed by treating trees with 100ppm at 40% leaf fall or 50ppm at both 40 and 70% leaf fall the previous autumn.
Clingstone peach [Prunus persica (L.) Batsch cv. Allgold] trees were fertilized once with 45 or 90 kg N/ha at budbreak or twice with 22.5 or 45 kg N/ha at budbreak and after harvest. A nonfertilized control was included. Fruits from all treatments were made into puree, and objective and subjective qualities were evaluated. Puree from the N treatments and the control did not show significant differences in Color Difference Meter (CDM) `L' and hue angle, pH, titratable acidity (TA), soluble solids concentration (SSC), SSC: TA ratio, viscosity, ascorbic acid, Ca, K, phenolic and nitrates concentration. Puree from the control and 22.5 kg N/ha applied twice had significantly lower CDM `a', `b', and chroma values than from the other treatments. The split applications of N significantly reduced levels of Ca and ascorbic acid. N rate and number of applications interacted for `a' and K. When N was applied twice at 22.5 kg·ha-1, `a' and K decreased, but this response was absent when N was applied twice at 45 kg·ha-1. Puree from the nonfertilized control was rated lower by panelists for sensory quality than that from the fertilized trees. Peach puree from trees fertilized once with 45 kg N/ha at budbreak had the best overall sensory quality.
Light is important in the production of phenolic compounds because key enzymes in phenolic biosynthesis are induced by light, and because products of photosynthesis are used in the synthesis of phenolic compounds. It is known that light intensity decreases with increasing depth in apple tree canopies. The objective of this experiment was to determine how leaf position on a limb affects the total foliar phenolic content. Leaves from `Stark Spur Supreme Red Delicious' on C6 and M26 rootstocks were collected on 28 July and 2 Aug. 1996. Each tree was divided into two sides, east and west. Each side was divided into 3 areas; exterior, middle, and interior. From each area, leaves were collected and PAR, SLW, assimilation, total N, and total phenolics were measured. Leaf position on a limb was a significant parameter for all of the measured variables. PAR, SLW, assimilation, total N, and total phenolics were highest in leaves at the exterior of the canopy. The total foliar phenolic content of the exterior canopy leaves was 20% higher than that found in the interior canopy leaves. There was a significant correlation between SLW and total phenolic content/cm2(r 2 = 0.77; P < 0.05). Assimilation may be a limiting factor in phenolics production in apple trees because of the correlation between assimilation and total phenolic content/cm2 (r2=0.56, P < 0.05).
A multidisciplinary effort has been initiated between the University of Arkansas and the National Center for Appropriate Technology to identify production barriers, research and outreach needs, and market opportunities for sustainable and organic fruit in the Southern region. The goals of the project are to identify barriers of the organic system through focus group meetings with producers, processors and marketers, and to develop regional research and outreach projects to overcome these obstacles. Market development, organic fertilizer knowledge and organic pest management have been identified as areas that need research and outreach activities. Long-term outcomes are expected to increase sustainable and organic fruit production, provide opportunities for growers and consumers, and encourage local economic development in the Southern region.