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Cayenne pepper fruit adhere tightly to the calyx/receptacle, increasing the cost of hand harvest and restricting mechanical harvest. Eight (8) cayenne pepper genotypes were selected from field observations to characterize fruit detachment forces(FDFs) and examine potential relationships between FDF and other fruit parameters. A preliminary greenhouse experiment revealed two genotypes with consistently lower FDFs and two with consistently higher FDFs over several progressive harvest. A field experiment confirmed these characteristics. No correlation between any fruit parameter and FDF was found to be consistent over the genotypes studied.

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Abstract

The cotyledons of pecan [Carya illinoensis (Wang.) K. Koch] seed remain fleshy and turgid throughout an attachment period of several weeks after germination. The growth (dry weight) of the developing seedling was dependent on the cotyledons for the first 3 weeks of the 6–10 week attachment period.

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Young sweet cherry (Prunus avium) trees are typically upright, vegetatively vigorous, and nonprecocious, taking 5 to 6 years to come into production. To produce fruit in high-density orchards by year 3 or 4, development of lateral shoots for potential fruiting is critical in year 2 or 3. An experiment was designed to promote lateral branching on 2-year-old trees. The experiment was conducted in a commercial orchard in Roosevelt, Wash., with `Bing' and `Van' on the vigorous rootstocks Mazzard and Colt. The trees were planted at 415 trees per acre with three scaffolds trained into a “V” canopy design. The experimental variables were treatments with and without Promalin (1.8% BAP plus 1.8% GA4+7), applied at a ratio of 1:3 in latex paint at green tip stage; superimposed on these treatments were either heading cuts of each scaffold to 2 m long (or tipping the scaffold if it was <2 m), removing four to five buds subtending the terminal bud, a combination of heading and bud removal, or controls. On trees that were not treated with Promalin, three additional treatments included either removing subtending buds at budbreak, or removing buds at multiple locations along the scaffold at green tip or at budbreak. New lateral shoots were counted 4 weeks after budbreak, and the quality of the shoots (shoot diameter and angle of emergence) was measured at the time of summer pruning. Interactions between Promalin, bud manipulation, and pruning will be discussed in relation to development of canopy structure.

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Commercially-produced, endodormant `Gloria' azaleas were placed into temperature × duration dormancy-breaking treatments at 2 month intervals to characterize seasonal variation in floricultural performance. Given the standard industry practice to break bud dormancy is 6 weeks at 3.5 to 7.2 C, three temperatures (3.5, 7.5, 11.5 C) and four durations (2, 4, 6, 8 weeks), plus a non-chilled control, were used to examine the contribution of each dormancy-breaking factor to subsequent floricultural quality. Treatment-Induced leaf abscission and flowering were quantitated, including days to Initial flowering and 50% flowering. Flowering response of dormant-budded azaleas produced during late spring and early summer (chilled during summer and early fall, respectively) was primarily and positively related to chilling duration, with only a minor influence of chilling temperature. In contrast, flowering of fall-produced endodormant plants (chilled during late fall) was best at 3.5 C, regardless of duration. Across all intervals, control plants averaged a leaf loss rate of 3 to 4 per day, suggesting a steady-state turnover rate. While leaf abscission was higher in all chilling-treated plants, those produced during fall and given the standard (or longer) chilling treatment exhibited about twice the total abscission (averaging as much as 20 leaves per day) as plants produced at other times, resulting in a clear reduction in plant foliar quality.

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Year-round production of the florist azalea cv. Gloria is limited by non-uniform flowering in fall-produced, endodormant-budded plants. To examine the effects of the standard dormancy-breaking chilling treatment (six weeks at 3.5 C) on carbohydrate metabolism, single-cutting plants were chilled in low light (10 μmol·m-2s-1) or in continuous dark Treatment effects were studied by destructively harvesting canopy organs for dry weight and carbohydrate analysis at two week intervals during treatment and at five day intervals during greenhouse forcing. Flowering performance was also evaluated. No differences were found between the low light or continuous dark chilling treatments for canopy organ dry weights, days to initial flowering, or days to 50% flowering. Leaf dry weight decreased 22% during chilling, and did not recover to pre-treatment levels through 15 days of forcing. Stem dry weights did not change during treatment or forcing. Floral bud dry weights were maintained during treatment and increased during forcing. Analysis of soluble carbohydrates indicated that the low light treatment influenced carbohydrate metabolism, resulting in Increased concentrations of sucrose, fructose, and glucose in all canopy organs compared to the dark treatment Maltose concentrations were higher in the light for leaves and stems, but not buds. The potential significance of these changes, with respect to dormancy-breaking treatments and uniform flowering performance, will be discussed.

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A detached leaf disk assay for screening sweet cherry (Prunus avium L.) genotypes for susceptibility to powdery mildew (PM) [Podosphaera clandestina (Wallr.:Fr.) Lev.] was developed by evaluating the effects of photoperiod (24 hours light, 0 hours light, 14 hours light/10 hours dark), substrate nutrient content (sterile distilled water, 1% sucrose), leaf age (old, young, emergent), and leaf explant size (intact leaf, 30 mm, 20 mm) on PM growth on leaves from the susceptible cultivar Bing. The only parameter described that had a significant (P ≤ 0.001) effect on PM growth was leaf age. Old leaves, designated as the third fully expanded leaf from the basal end of current-year's shoot growth, were never infected with PM under controlled inoculations. In the absence of significant differences between treatments, those parameters with the highest treatment means were selected for subsequent evaluation. To test the leaf disk assay, 14 sweet cherry cultivars were screened in two experiments, and rated according to level of PM susceptibility. Rank sum comparison of results from cultivars used for leaf disk screening agreed with earlier field rankings of the same cultivars. The developed leaf disk assay greatly reduced the space required to screen sweet cherry cultivars, and was a repeatable and objective predictor of field resistance that may be useful for screening germplasm or breeding populations.

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Flower initiation and development in `Bing' sweet cherry (Prunus avium L.) was examined using scanning electron microscopy. There was a 1- to 2-week difference in the time of initiation of flower buds on summer pruned current season shoots (P) compared to buds borne on unpruned shoots (U) or spurs (S). By late July, this difference was obvious in morphological development. The P buds had already formed floral primordia, while the S and U buds showed little differentiation in the meristem until early August. In general, buds from unpruned shoots were similar developmentally to spur buds. By late August, primordial differentiation was similar in the buds from all the wood types; however, buds from pruned shoots were significantly larger (838 μm) than buds from spurs (535 μm) and unpruned shoots (663 μm). Early summer pruning may shift allocation of resources from terminal shoot elongation to reproductive meristem development at the base of current season shoots. The similarity in reproductive bud development between spurs and unpruned shoots, given the difference in active terminal growth, might suggest that developmental resources are inherently more limiting in reproductive buds on spurs.

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Of eight genotypes of cayenne pepper (Capsicum annuum L.) examined, two were identified that differ significantly in ease of fruit detachment force. Greenhouse and field-grown plants of these genotypes, Cajun 1-9027 and Cap-9004, were investigated for differences in cell type and organization at the fruit and receptacle junction. Scanning electron microscopy revealed that mature Cajun 1-9027 fruit that did not separate exhibited a distinct region of sclerified cells that extended from the periphery of the fruit into the receptacle for 25 to 30 cell layers. In contrast, mature fruit of the more readily detachable Cap-9004 had 10 to 15 layers of sclerified cells at the region of detachment. Histochemical and stereological techniques indicated that Cajun 1-9027 had a greater volume of sclereids than Cap-9004. Cajun 1-9027 exhibited smaller cortical cells in the detachment region than Cap-9004. Neither genotype exhibited a well-defined abscission zone at maturity in the detachment region. The presence of more sclerified cells and increased lignification in Cajun 1-9027 compared to Cap-9004 probably contributed to the differences in ease of detachment between the two genotypes.

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Premature leaf blackening in Protea severely reduces vase life and market value. The current hypothesis suggests that leaf blackening is induced by a sequence of events related to metabolic reactions associated with senescence, beginning with total depletion of leaf carbohydrates. It is thought that this carbohydrate depletion may induce hydrolysis of intercellular membranes to supply respiratory substrate, and subsequently allow vacuole-sequestered phenols to be oxidized by polyphenol oxidase (PPO) and peroxidase (POD) (Whitehead and de Swardt, 1982). To more thoroughly examine this hypothesis, leaf carbohydrate depletion and the activities of PPO and POD in cut flower Protea susannae × P. compacta stems held under light and dark conditions were examined in relationship to postharvest leaf blackening. Leaf blackening proceeded rapidly on dark-held stems, approaching 100% by day 8, and was temporally coincident with a rapid decline in starch concentration. Blackening of leaves on light-held stems did not occur until after day 7, and a higher concentration of starch was maintained earlier in the postharvest period for stems held in light than those held in dark. A large concentration of the sugar alcohol, polygalatol, was maintained in dark- and light-held stems over the postharvest period, suggesting that it is not involved in growth or maintenance metabolism. Polyphenol oxidase activity in light- and dark-held stems was not related to appearance of blackening symptoms. Activity of PPO at pH 7.2 in light-held stems resulted in a 10-fold increase over the 8-day period. Activity in dark-held stems increased initially, but declined at the onset of leaf blackening. There was no significant difference in POD activity for dark- or light-held stems during the postharvest period. Total chlorophyll and protein concentrations did not decline over the 8-day period or differ between light- and dark-held stems. Total phenolics in the dark-held stems increased to concentrations ≈30% higher than light-held stems. Consequently, the lack of association between membrane collapse, leaf senescence, or activities of oxidative enzymes (PPO or POD) with leaf blackening does not support the hypothesis currently accepted by many Protea researchers. An alternative scenario may be that the rapid rate of leaf starch hydrolysis imposes an osmotic stress resulting in cleavage of glycosylated phenolic compounds to release glucose for carbohydrate metabolism and coincidentally increase the pool of free phenolics available for nonenzymatic oxidation. The physiology of such a carbohydrate-related cellular stress and its manifestation in cellular blackening remains to be elucidated.

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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”.

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