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  • Author or Editor: L. H. Fuchigami x
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Abstract

Rhododendron leaf disks (Rhododendron L., cv. Jean Marie de Montague) release water-soluble phenolic compounds when subjected to lethal freezing stress. Following low-temperature exposure, the levels of phenolic compounds leached from the disks are assessed by spectrophotometric measurement (260 nm). The increase in phenolics is highly correlated with other viability tests—electrolyte leakage, visual browning, ethane production, and TTC reduction have r values of 0.99, 0.99, 0.95, and −0.88, respectively. Chemical names used: Trichloroacetic acid (TCA), polyvinylpolypyrrolidone (PVPP), 2,3,5-triphenyl tetrazolium chloride (TTC).

Open Access

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.

Free access

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.

Open Access

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.

Open Access

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.

Open Access

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.

Open Access

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.

Open Access

Abstract

Excised Cornus stolonifera Michx. stems cultured axenically in a liquid medium were acclimated to cold when subjected to short photoperiods and low temperatures. Foliate explants acclimated effectively and defoliated ones did not when they were cultured on White's medium which contained 0.083 M sucrose. Several other concentrations of sugars (0, 0.01, 0.1, and 0.5 M glucose and 0, 0.01, 0.05, and 0.1 M sucrose) did not enhance cold acclimation of foliated explants. The exogenously supplied sugars reduced stem growth, promoted leaf abscission, and enhanced the development of typical autumnal red coloration in leaves and stems. The highest sugar concentration (0.5 M glucose) caused death of the explants.

While a minimal level of photosynthate (sugar) is almost certainly required for the active metabolic phases of cold acclimation in hardy woody species, our studies provided no evidence that sugars bear a direct causal relationship to cold acclimation.

Open Access

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.

Free access

Abstract

This study examined the leaf anatomy and water stress of Prunus insititia L. cv. Pixy grown in aseptic culture before and after transfer to the greenhouse and grown in a layerage bed in the field. The depth of palisade cells was significantly less in aseptically cultured plantlets than in greenhouse transfererred plants, and less in greenhouse transferred than in field-grown plants. Percent mesophyll air space was greater in plantlet than in plant leaves. Upper or lower leaf epidermal cell length of plantlets of field grown plants was not significantly different. Stomatal frequency for plantlet leaves was significantly less about 150 stornata per mm2) than that of plant leaves (300 stornata per mm2). Excised plantlet leaves lost greater than 50% of total leaf water content within 30 min; excised greenhouse leaves lost 50% after 90 minutes.

Open Access