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  • Author or Editor: L. H. Fuchigami x
  • Journal of the American Society for Horticultural Science x
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Abstract

The effectiveness of (2 chloroethyl)phosphonic acid (ethephon) in inducing defoliation and in delaying spring bud growth of red-osier dogwood was related to the time of application. Plants treated with ethephon before they matured were not effectively defoliated. Mature plants were effectively defoliated and ethephon’s effectiveness increased progressively at subsequent treatment dates. Ethephon treatments applied on September 29, October 6 and 13, delayed spring bud break by 7, 5, and 3 days respectively. Hand defoliation on the same dates induced identical delays in spring growth.

Open Access

Abstract

Rooted cuttings of a clonal selection of Salix purpurea L. were grown in perlite, in a warm greenhouse at natural daylengths and irrigated daily with one of 10 different mineral nutrient solutions. Plants from each of the nutrient treatments were hand defoliated at weekly intervals beginning in August to assess the effects of mineral nutrients on vegetative maturity development. Vegetative maturity was quantified the following spring by measuring stem dieback. Plants in some nutrient treatments ceased growing 9 weeks earlier in the autumn, and became vegetatively mature several weeks sooner than plants in other treatments. Specifically, treatments such as the distilled water control and Hoagland solution -N,-P, and -S induced early growth cessation, resulted in less stem growth, and induced early onset of vegetative maturity as evidenced by reduced stem dieback the following spring. Development of vegetative maturity was slower in plants irrigated with complete Hoagland solution or Hoagland solution -Ca, -Mg, and -K, which continued growing until October when natural defoliation and growth cessation occurred on control plants treated with complete Hoagland solution. The study demonstrates that vegetative maturity in S. purpurea can be hastened by witholding N, P, and S.

Open Access

Abstract

Ethylene evolution from excised plant parts was tested as an indicator of stage of seasonal development in red-osier dogwood (Cornus sericea L., syn. C. stolonifera Michx.). A reduction in ethylene production occurs several weeks prior to the time when defoliation can be safely accomplished. This reduction occurs synchronously over the length of the plant, although ethylene production by basipetal tissues prior to the decrease was lower than that by more acropetal tissues. The pattern of change in ethylene production by nodal tissue, which included the axillary buds and about 5 mm of petiole, seemed to be least affected by environmental growing conditions. Ethylene could be used as a predictor for vegetative maturity stage in red-osier dogwood.

Open Access

Abstract

The title and byline of the paper, The Relationship between Vegetative Maturity and the First Stage of Cold Acclimation by P. C. Nissila and L. H. Fuchigami (J. Amer. Soc. Hort. Sci. 103(6):710-711. 1978), was inadvertently omitted from the table of contents.

Open Access

Abstract

Electrical impedance ratios and water contents were measured during the development of vegetative maturity and dormancy in a clone of red-osier dogwood Cornus sericea L.) on plants exposed to 16 hour and 12 hour photoperiods in growth chambers to selectively prevent or induce dormancy. Vegetative maturity was designated as the point at which buds were no longer stimulated to grow following artificial defoliation. After this time the ratio of impedance values obtained from the frequencies 10 kHz:100kHz increased and tissue water decreased. Electrical impedance ratios were more easily measured and showed less variation between plants. We conclude that electrical impedance ratios are a means of identifying the onset of vegetative maturity and dormancy in woody deciduous species.

Open Access

Abstract

Ethylene and ethane production of freeze-stressed rhododendron (Rhododendron sp. ‘Sappho’) leaf disks were compared to visual rating, TTC reduction, and electrolyte leakage as possible means of measuring tissue viability. Ethane production, as caused by freezing temperatures, was highly correlated with visual rating, TTC reduction, and electrical conductivity (r = 0.96, r = −0.81, and r = 0.96, respectively). Ethylene production peaked concurrently with initial stages of visual tissue damage, then decreased as the temperature was lowered until complete death occured. Ethane production and electrolyte leakage peaked coincidentally with the decrease of ethylene. Ethylene:ethane ratios are suggested as a measurement of freeze-induced tissue damage. This study supports the view that ethylene production is related to stress and ethane production to cell death. Chemical names used: 2,3,5-triphenyltetrazolium chloride (TTC).

Open Access

Abstract

Aseptically cultured Malus domestica (Borkh.) cv. Mac 9 plants were exposed to 30–40% relative humidity (RH) for 0 to 6 days. The relative water content (RWC) and percent stomatal closure were measured on leaves excised from plants exposed to low humidity and from greenhouse acclimatized controls. Both RWC and percent stomatal closure successfully monitored acclimatization. The RWC of excised leaves exposed to low RH for 0 or 1 day was significantly higher than that of leaves exposed for 4.5 days or of greenhouse-acclimatized plants. Speed of stomatal closure upon leaf excision increased with the duration of plant exposure to low humidity. The rate of water loss from excised apple leaves was linearly related to the stomatal closure. Aseptically cultured plant (ACP) leaves consistently lost more water than greenhouse leaves at corresponding percentages of stomatal closure. These results indicated that ACP leaves can be acclimatized to low humidity within 4 to 5 days of exposure to 30 to 40% RH and that low humidity acclimatization involved development of an accelerated stomatal response.

Open Access

Abstract

Potted plants of red-osier dogwood (Cornus sericea L., syn. C. stolonifera Michx) were grown under 3 different dormancy-inducing regimes. Each week 5 plants per group were defoliated and placed in a warm greenhouse. Plants were checked daily for regrowth and new leaves were removed. When defoliation ceased to induce bud break, the plants were considered to be in a state of winter dormancy. Plants were observed for damage the following spring to determine when they had reached vegetative maturity, and it was found that vegetative maturity corresponded to winter dormancy development in all 3 growing conditions.

Open Access

Abstract

Xylem water potential (XWP) and electrical impedance ratios were used to determine the time of vegetative maturity in red-osier dogwood (Cornus stolonifera Michx.) grown under 2 temperature and a short-day dormancy inducing regime in growth chambers and a lathhouse under natural conditions. The decline in XWP correlated with the development of vegetative maturity as measured by tip dieback after defoliation. Under growth chamber conditions, average XWP values reached a minimum at the time of vegetative maturity. In all cases, however, variability within samples was so large as to preclude the use of XWP as an accurate, reliable index of vegetative maturity. A change in electrical impedance ratios at and after vegetative maturity caused the impedance meter to go “off scale.” Compared with XWP values, changes in electrical impedance ratios were more consistent and show promise in predicting vegetative maturity.

Open Access

Abstract

Red-osier dogwood (Cornus stolonifera Michx.) plants were grown outdoors in a lathhouse to study the relationship between vegetative maturity and the first stage of cold acclimation. Both microscopic observations and electrical impedance ratios used to measure damage of frozen stem sections verified the close association of the onset of the first stage of cold acclimation and vegetative maturity. The relationship of these processes to dormancy development is discussed.

Open Access