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  • Author or Editor: L. H. Fuchigami x
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Temperate woody perennials produce proteins in the stem for seasonal nitrogen (N) storage. In Populus species, this seasonal N storage occurs primarily as a 32-kDa Bark Storage Protein (BSP), which can accumulate to 50% of total bark proteins during the winter. Plants of the Populus tremula × Populus alba (clone 717) were transformed with the BSP cDNA in antisense orientation (fused to a constitutive promoter), and regenerated lines were screened. Several independent antisense-BSP (A-BSP) lines were selected, which, after 4 weeks of SD photoperiod, showed 70% to 90% reduction in total BSP accumulation compared to the wild-type (WT). A series of experiments were conducted to compare LD growth of one A-BSP line to that of the WT. A-BSP plants showed reduced growth at both 5 and 50 mM ammonium nitrate fertilization. However, the higher N rate eventually resulted in toxicity in WT, but not in A-BSP plants. A-BSP plants grown hydroponically (0.5x Hoagland1s) showed altered partitioning with reduced stem length and increased leaf area (Leaf:stem dry-weight ratios were 14.8 and 20.9 for ABSP and WT, respectively). Partitioning to the roots was not different between A-BSP and WT. Proposed functions of BSP in seasonal and LD nitrogen metabolism will be discussed.

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Abstract

Rest period, the transition between summer and winter dormancy, and vegetative maturity were studied in red-osier dogwood (Cornus stolonifera Michx.) in Oregon. Maximum rest occurred in late October and early November when 180 days were required for growth resumption under favorable growing conditions. The transition between summer dormancy (correlative inhibition of lateral buds) and winter dormancy (onset of rest) occurred in early September, 21 days before maturity, 49 days before natural leaf abscission, and 56 days before maximum rest. Lateral buds of plants defoliated prior to this transition grew within 10 days while buds of plants defoliated after that date did not resume growth until spring. Vegetative maturity was achieved in late September. Plants defoliated after that time overwintered without apparent injury. Spring regrowth was normal in mature plants, but bud-break was delayed as much as 10 days as a result of defoliation the previous autumn. Vegetatively immature plants defoliated before late September died outright or sustained varying degrees of stem dieback. Natural leaf abscission occurred in late October, 49 days after plants were vegetatively mature. The extent of stem dieback was inversely related to stage of maturity, a relationship that provides a useful means of quantitatively expressing when, and to what extent, plants are mature.

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Abstract

Scanning electron microscopy was used to investigate leaf epicuticular wax of Prunus instititia L. ‘Pixie’ from aseptically cultured plants before and after acclimatization to the greenhouse. Leaves from plants acclimatized for 2 weeks in the greenhouse had more adaxial wax than those from non-acclimatized (culture flask-grown) plants. Acclimatized plants had more adaxial than abaxial wax. No abaxial wax was observed on leaves of non-acclimatized plants. Stomata were present on the abaxial leaf surface only of both acclimatized and non-acclimatized plants. Epicuticular wax layers surrounded guard cells of acclimatized plant leaves but were not present on non-acclimatized plant leaves. Weight changes in non-acclimatized plant leaves coated with silicon rubber on adaxial, abaxial, and both surfaces indicated that excised leaf water loss occurred only through the abaxial surface. Water loss from plants during the acclimatization process thus may be due to abaxial cuticular and stomatal transpiration.

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Abstract

Ethylene and ethane production and electrolyte leakage were determined during water stress of leaves of asceptically-cultured plum (Prunus insititia L. cv. Pixy). Ethylene production increased to a maximum at about 50% leaf water loss and decreased as water deficit increased. Ethane production and electrolyte leakage were highly correlated, increasing only after 50% water loss to a maximum at about 72% water loss, indicating an increase in cell injury and death.

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Abstract

Attempts to measure and interpret the attenuation of electrical square waves in red-osier dogwood (Cornus series L.) and apple (Malus sp.) indicate that the difficulties of interpreting and obtaining reproducible quantitative data makes them of little value as criteria of dormancy in woody plants.

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Abstract

Hydrogen cyanamide or hot-water treatment (47C) for 1 hr at the 250°GS (Growth Stage) effectively broke rest in dogwood buds within 10 to 12 days. At this growth stage, control plants grown at 25/18C (day/night) maintained an LT50 of –25C throughout the 3-week study period, whereas plants treated with H2CN2 or hot water gradually lost hardiness. After 3 weeks at 5/2C (day/night), the control plants hardened to a hardiness (LT50) of –45C, and H2CN2-treated plants maintained an LT50 of –25C. The results demonstrate that the extent of acclimation and deacclimaton of dogwood plants may be influenced by environmental temperatures and rest status.

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Abstract

Ethephon at 120 mg·liter−1 applied to hand-defoliated or nondefoliated trees in late Oct. 1984 delayed ‘Redhaven’ [Prunus persica (L.) Batsch.] full bloom by ≈5 days in 1985. The same treatment applied on 1 Nov. 1985 delayed full bloom by 9 days in 1986. Hand-defoliation alone was ineffective in delaying bloom in either season. Ethephon treatments increased abscisic acid (ABA) and ethylene levels in dormant buds collected throughout the 1985–86 dormant season. Starch and reducing sugar contents and total chilling requirement were not affected by the ethephon and hand-defoliation. Flower primordia were delayed in differentiation and growth during late fall following a 1986 spray of ethephon. A delay in flower development and growth may be caused by increased levels of ethylene and ABA. Chemical names used: (2-chloroethyl) phosphonic acid (ethephon); aminoethoxyvinylglycine (AVG).

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Previously, we reported recovery of plants from “Near-Lethal” (NL) (Sub-Lethal) stresses was dependent on stage of development and post-stress environment Dormant plants exposed to NL-heat, freezing, and hydrogen cyanamide either died or were severely injured when stored at 0°C or recovered at 23°C and natural condition. This study reports on the changes in the evolution of metabolic heat in dormant red-osier dogwood (Cornus sericea L.) stem tissues after beat stress. Heat stress (51°C for half an hour) was followed by one of two post-stress environment (PSE) (0° or 23°C dark condition). Isothermal measurements of the heat of metabolism of the tissues were taken after 0, 1, 2, 5, 7 and 11 days of PSE. A significant reduction of metabolic heat generation occured in heat stressed plants at 0°C PSE from one to 11 days of incubation as compared to the non-stressed tissues. At 23°C PSE, no significant differences of heat generation between stressed and non stressed tissues were found within 7 days of incubation. The rate of metabolic. heat measured by decreasing temperature scanning microcalorimetry (21° to 1°C) were lower in beat stressed tissues. Arrhenius plots of metabolic heat rate gave a linear slope for non-stressed tissues and a complex slop for NL-stressed tissues at lower temperatures. Energy of activation (Ea) between 1°-8°C were 15.45 and 83.882 KJ mol-1 for NL-heat and non-stressed tissues, respectively.

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Recent field observations by growers suggest that increased nitrogen (N) content in nursery trees resulting from foliar sprays with urea in the autumn increases tree susceptibility to infection by Phytophthora syringae. We investigated the effects of soil N availability and spraying pear (Pyrus communis ‘OHF 97’) trees with combinations of urea, chelated copper ethylenediaminetetraacetic acid (CuEDTA), and phosphonate-containing fungicides on stem N concentration and susceptibility to infection by P. syringae. Increasing soil N availability increased susceptibility to P. syringae and increased N and amino acid concentration in stems. Spraying trees with urea in the autumn increased concentrations of N and amino acids in stems and had no significant effect on tree susceptibility when stems were inoculated with P. syringae before or after urea sprays. Spraying trees with CuEDTA decreased stem N concentrations and had no significant influence on tree susceptibility to P. syringae when stems were inoculated before or after CuEDTA sprays. These results suggest the relationship between tree susceptibility to P. syringae and tree N concentration may be specific to the form of N, delivery method, or timing of N applications. Trees had higher N concentrations in stems in November than in October and were more susceptible to P. syringae when inoculated in November, suggesting that environmental factors and increasing tree dormancy may be responsible for changes in susceptibility to the pathogen. Spraying trees with fungicides containing fosetyl-aluminum in October or November decreased tree susceptibility to P. syringae. The effects of fungicides containing fosetyl-aluminum on susceptibility were similar regardless of whether trees were sprayed or not with urea or CuEDTA, suggesting that these fungicides can be used in combination with urea or CuEDTA sprays for reducing disease severity caused by P. syringae without impacting growers' objective of increasing tree N content with urea or enhancing early defoliation with CuEDTA.

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Abstract

Inflorescence slices of tall bearded iris (Iris sp.) regenerated callus in vitro on a modified Murashige-Skoog high salt medium supplemented with 2.5 mg/liter napthaleneacetic acid (NAA) and 0.5 mg/liter kinetin. Callus pieces transferred to light initiated plantlets at their periphery and produced fuU-sized, true-to-type flowering plants when transplanted to soil.

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