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  • Author or Editor: Fumiomi Takeda Takeda x
  • Journal of the American Society for Horticultural Science x
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Differential thermal analyses (DTA) and freeze viability tests were conducted to investigate the biophysics of freezing in floral buds of `Danka' black (Ribes nigrutn L.) and `Red Lake' red currants [Ribe.s sativum (Rchb.) Syrne] sampled from Nov. 1989 through Mar. 1990. Scanning electron microscopy was also used to determine the relationship between floral morphology and the freezing characteristics of the buds. Floral buds had multiple abrupt low-temperature exotherms (LTEs) and one or two broad LTEs in DTA tests. Abrupt LTEs from DTA were associated with apparent injury to the inflorescence in viability tests. The number of LTEs did not correspond to the number of racemes or flowers per bud, indicating that several flowers froze simultaneously. DTA experiments conducted in Dec. 1990 revealed that the broad exotherm detected between - 14 and - 20C in `Danka' samples resulted from freezing of supercooled water in the outer nonliving region of the periderm of cane tissue attached to the bud.

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Abstract

Neither abscisic acid (ABA) levels in developing kernels nor in the developing inflorescence buds themselves were found to be related to abscission of inflorescence buds and consequent alternate bearing in pistachio (Pistacia vera L.).

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Abstract

Axillary buds on lateral branches of ‘Black Satin’ and ‘Hull Thornless’ thornless blackberries (Rubus sp.) were examined from September to May in 1984–1985 and 1986–1987, and in Spring 1988. Initial inflorescence development in ‘Black Satin’ was evident in October; however, most buds remained vegetative until January. Perianth primordia became distinct around the terminal floral apex in some buds in late February to early March. Buds sampled from lateral branches at the top portion of plants were more advanced than buds from the bottom portion at several sampling dates. Axillary buds of ‘Hull Thornless’, in contrast, remained vegetative in all floricane portions until late March. Subsequent developmental rates were rapid and uniform. Once the terminal flower appeared, the most basal floral apex in the primary (A1) axis was next to develop. Remaining floral apices along the axis developed sequentially in an acropetal direction. Neither uniformity and time of bud initiation nor subsequent rate of development appeared to affect the length of bloom period.

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Abstract

Movement of 14C-photosynthates in bearing and nonbearing branches of pistachio (Pistacia vera L.) was examined during the period of inflorescence bud abscission. Most of the 14C transported from leaves accumulated in developing nuts. Inflorescence buds on defruited trees accumulated twice as much 14C-photosynthate as those on fruiting trees. Inflorescence buds competed poorly against the developing fruit for photosynthate and this might be responsible for inflorescence bud abscission and resultant alternate bearing.

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Abstract

We found in light and scanning electron microscopic studies of buds of the pistillate ‘Kerman’ pistachio (Pistacia vera L.) that about 12 months elapsed from the time of inflorescence differentiation until the opening of individual flowers. Growth of the rachis and its lateral branches occurred from April to June; sepal differentiation, from late May to mid June; pistil initiation, from early October to March; and carpel development, from late March to early April. Cessation of the development of the inflorescence buds during July, August, and early September appears to be unrelated to nut growth and development, as buds were inactive during that period in both bearing and nonbearing trees.

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Flower bud development was studied in `Cherokee', `Boysen', and `Marion' blackberries (Rubus subgenus Rubus Watson). In `Cherokee' (erect type), the transition to reproductive development in buds on the branch canes occurred during September in Arkansas and Oregon. Transitions of buds in the axils of the most basal nodes (proximal to the main cane) and the most distal nodes lagged behind buds in the midsection (about nodes 6 to 10). Along the midsection of branch canes, the buds developed uniformly. In buds of `Boysen' and `Marion' (trailing type), the transition to reproductive development occurred in October and sepal primordia were observed in most buds examined by November. Progression of floral bud development continued into January, but at a slower rate than in autumn. Buds on the main canes (>3 m long) of `Boysen' and `Marion' remained at a more advanced stage of flower bud differentiation than buds on the basal branch canes. In both cultivars, buds from the middle one-third section, and sometimes buds from the bottom one-third section, tended to be more advanced than those buds in the top one-third section during much of the sampling period. The results suggest that rate and patterns of flower bud development vary among cultivars grown in different locations. However, the pattern of flower bud development was not in a basipetal fashion on main or branch canes.

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Transition to reproductive development and subsequent development of floral primordia (e.g., sepals, petals, stamens, and pistils) were determined in several blackberry (Rubus subgenus Rubus Watson) cultivars (Boysen, Cherokee, Chester Thornless, Marion, and Thornless Evergreen) growing in one or more locations (Clarksville, Ark., Aurora and Hillsboro, Ore., and Kearneysville, W. Va.). Also, daily maximum, mean, and minimum temperatures were recorded at three sites (Clarksville, Aurora, and Kearneysville) for the September to April sampling period. In buds of `Boysen' and `Marion' from Oregon, sepal primordia were first observed in November and December, respectively. Further floral bud development continued into January. Sepal development in `Cherokee' buds occurred in October in Oregon and in December in Arkansas. At all three sites, the buds of `Chester Thornless' blackberry remained undifferentiated until spring. The average mean temperatures in Oregon were generally well above 5 °C during the bud sampling period, but were near 0 °C on most days from mid-December to January in Arkansas and from December to late-February in West Virginia. The phenology of flower bud differentiation varied among the cultivars and was strongly influenced by prevailing winter temperatures. The results suggest that the shortening day lengths of late summer trigger flower bud development in blackberry. Floral bud development in blackberry, once initiated, was continuous; however, periods of low temperature (<2 °C) can arrest development.

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Hydathodes of young, folded strawberry (Fragaria × ananassa Duch.) leaves had unoccluded water pores With various sized apertures, as observed by low-temperature scanning electron microscopy. Hydathodes of fully expanded leaves were brownish and the water pores within the hydathodes were covered with a solid material, presumably comprised of epicuticular waxes and substances excreted through the hydathodes. The entire water pore area of the hydathode was occasionally covered with a shield-like plate. The shield-like plate over the hydathode water pores impeded water flow even with an induced positive pressure. Mechanical scraping of the hydathode area eliminated impedance to water conduction. These observations suggest that external occlusion of water pores in the hydathodes is the resistance component associated with the absence of guttation in older strawberry leaves.

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`Hull Thornless' and `Black Satin' blackberry (Rubus spp.) canes were collected from Sept. 1989 through Mar. 1990 to determine the hardiness and supercooling characteristics of buds at various stages of development. Anatomical studies were also conducted to examine the location of ice voids in buds frozen to -5 or -30C. Differentiation of the terminal flower occurred in `Black Satin' buds by 6 Nov., whereas `Hull Thornless' buds remained vegetative until early spring. As many as nine floral primordia were observed in both cultivars by 12 Mar. The hardiness of the two cultivars was similar until February. Thereafter, `Black Satin' buds were more susceptible to cold injury than those of `Hull Thornless'. Flora1 and undifferentiated buds of both cultivars exhibited one to four low temperature exotherms (LTEs) from 9 Oct. to 12 Mar. in differential thermal analysis (DTA) experiments. The stage of flora1 development did not influence the bud's capacity to supercool. The number of LTEs was not related to the stage of floral development or to the number of floral primordia. Extracellular voids resulting from ice formation in the bud axis and scales were observed in samples subjected to -5 or -30C.

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The effects of preharvest applications of pyrrolnitrin (a biologically derived fungicide) on postharvest longevity of `Bristol' black raspberry (Rubus occidentals L.) and `Heritage' red raspberry [R. idaeus L. var. strigosus (Michx.) Maxim] were evaluated at two storage temperatures. Preharvest fungicide treatments were 200 mg pyrrolnitrin/liter, a standard fungicide treatment (captan + benomyl or iprodione) or a distilled water control applied 1 day before first harvest. Black raspberries were stored at 18 or 0 ± lC in air or 20% CO2. Red raspberries were stored at the same temperatures in air only. Pyrrolnitrin-treated berries often had less gray mold (Botrytis cinerea Pers. ex Fr.) in storage than the control but more than berries treated with the standard fungicides. Storage in a modified atmosphere of 20% CO2 greatly improved postharvest quality of black raspberries at both storage temperatures by reducing gray mold development. The combination of standard fungicide or pyrrolnitrin, high CO2, and low temperature resulted in more than 2 weeks of storage with less than 5% disease on black raspberries; however, discoloration limited marketability after≈ 8 days under these conditions. Chemical names used: 3-chloro-4-(2'-nitro-3'-chlorophenyl) -pyrrole (pyrrolnitrin); N-trichloromethylthio-4-cyclohexene-l12-dicarboximide (captan); methyl 1-(butylcarbamoyl) -2-benzimidazolecarbamate) (benomyl); 3-(3,5 -dichlorophenyl) -N-(l-methylethyl -2,4-dioxo-l-imi-dazolidinecarboxamide (Rovral, iprodione).

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