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  • Author or Editor: Leslie H. Fuchigami x
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Many seeds of woody plants require low temperature or other treatments to overcome dormancy. Changes in catalase activity and glutathione has been proposed to be associated with the breaking of dormancy. We examined the level of glutathione and catalase activity of cherry seeds (Prunus mahaleb cv. Lambert) exposed to several dormancy breaking agents. Seeds imbibed in water for 24 hrs. were either stratified at 4°C or at 25°C for up to 12 weeks, or exposed to other dormancy breaking agents. Germination test, glutathione and catalase activity were determined weekly and/or after treatment. Analysis of levels and state of glutathione were performed by high pressure liquid chromatography (HPLC), and catalase activity was assayed spectrophotometrically. Total glutathione in dry and imbibed seeds were similar, but, ratio between the reduced and oxidized form were different. Low temperature stratification for 12 weeks increased the reduced form of glutathione six-fold, while percent germination increased up to 94%.

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In previous work, we have shown that near-lethal heat stress can overcome dormancy in Red-osier dogwood, Cornus sericea L. The objective of this study was to determine the effects of premature breaking of dormancy on the development of cold hardiness. Plants at three stages of dormancy (early, deep, and late) were exposed to 47C for one hour and then placed into 3 post-treatment environments (0C, 23C, and natural conditions). At periodic time intervals, the plants were evaluated for bud break, cold hardiness, and stem injury. These studies suggest that premature breaking of dormancy at the early stage had no effect on hardiness development, whereas at the deep and late stages of dormancy, premature breaking of dormancy caused a faster rate of deacclimation at the warmer post-treatment environments. In addition, we observed that the heat-treated plants died during storage at 0C, and survived at 23C storage and natural conditions.

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Red-osier dogwood sterns, Cornus sericea L., at ten different growth stages were subjected to a series of temperatures ranging from 25C to 60C by immersing them in a water bath for one hour. After heat treatments, the viability of internode tissues were determined by electrical conductivity and ethylene production. Heat tolerance was expressed as LT50, the temperature at which 50% of the tissues were injured. The results suggest that the LT50 of dormant plants remained relatively constant, approximately 53C. During dormancy, heat stress did not stimulate ethylene production from internode tissues. In contrast, tissues from non-dormant plants exposed to heat stress produced increasing levels of ethylene reaching a peak at 40C followed by a steady decrease at higher temperatures. Application of 1-aminocyclopropane-1-carboxylic acid (ACC) to stem segments from dormant plants, following heat treatment, enhanced production of ethylene.

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Seedling plugs of `Better Boy' tomato plants (Lycopersicon esculentum Mill.) were potted in processed fiber:perlite (60:40% by volume) media amended or nonamended with either crystalline or powdered hydrophilic polymer (2.4 kg·m–3), and treated with one of the several concentrations (0, 2.5, 5, 7.5, and 10%) of antitranspirant GLK-8924, at the four true-leaf stage. Plants were either well-irrigated or subjected to short-term water stress, water withholding for 3 days, after antitranspirant GLK-8924 application. Leaf stomatal conductance, transpiration rate, whole plant transpirational water loss, and growth were depressed by short-term water stress and antitranspirant GLK-8924. In contrast, hydrophilic polymer amendment increased plant growth, resulting in higher transpirational water loss. The depression of stomatal conductance and transpiration rate by short-term water stress was reversed completely in 2 days after rewatering while the reduction of plant growth rate diminished immediately. The effects of antitranspirant GLK-8924 were nearly proportional to its concentration and lasted 8 days on stomatal conductance and transpiration rate, 4 days on plant growth rate, and throughout the experimental period on plant height and transpirational water loss. Plant growth was reduced by antitranspirant GLK-8924 possibly by closing leaf stomata. In contrast, hydrophilic polymer amendment resulted in larger plants by factors other than influences attributed to stomatal status. Hydrophilic polymer amendment did not interact with antitranspirant GLK-8924 on all variables measured. The application of antitranspirant GLK-8924 was demonstrated to be useful for regulating plant water status, plant growth and protecting plants from short-term water stress.

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Seedling plugs of `Better Boy' tomato plants (Lycopersicon esculentum Mill.) were potted in 60% processed fiber: 40% perlite (by volume) media amended or nonamended with either crystalline or powdered hydrophilic polymer (2.4 kg·m-3), and treated with one of several concentrations (0%, 2.5%, 5%, 7.5%, and 10%) of antitranspirant GLK-8924, at the four true-leaf stage. Plants were either well-irrigated or subjected to short-term water stress, withholding water for 3 days, after antitranspirant GLK-8924 application. Leaf stomatal conductance, transpiration rate, whole-plant transpirational water loss, and growth were depressed by short-term water stress and antitranspirant GLK-8924. In contrast, hydrophilic polymer amendment increased plant growth, resulting in higher transpirational water loss. The depression of stomatal conductance and transpiration rate by short-term water stress was reversed completely in 2 days after rewatering while the reduction of plant growth rate diminished immediately. The effects of antitranspirant GLK-8924 were nearly proportional to its concentration and lasted 8 days on stomatal conductance and transpiration rate, 4 days on plant growth rate, and throughout the experimental period on plant height and transpirational water loss. Plant growth was reduced by antitranspirant GLK-8924 possibly by closing leaf stomata. In contrast, hydrophilic polymer amendment resulted in larger plants by factors other than influences attributed to stomatal status. Hydrophilic polymer amendment did not interact with antitranspirant GLK-8924 on all variables measured. The application of antitranspirant GLK-8924 was demonstrated to be useful for regulating plant water status, plant growth, and protecting plants from short-term water stress.

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Nitrogen is one of the most important nutrition factors affecting grapevine growth performance and berry quality. Leaf pigments contents and leaf areas are the important indicators of grapevine nitrogen status and plant performance. In order to find a efficient way to nondestructively measure leaf nitrogen and pigments status, the SPAD meter, CCM-200 and CM-1000 chlorophyll meter in comparisons with FOSS NIR system were used in measuring leaf nitrogen, leaf chlorophyll, carotenoids, flavonoids and anthocyanins in 7-year-old Pinot Noir grape with different rate of N treatments. The results indicate that the reading of all these meters have a good relationship with leaf N, leaf chlorophyll and leaf area. But the accuracy among these meters was different, in which the accuracy of FOSS NIR is better than that of the SPAD meter, CCM-200 and CM-1000. There is the good relationship between leaf nitrogen contents, leaf area, leaf chlorophyll and carotenoids contents. Flavonoids and anthocyanins have the inverse relationship with leaf N contents and leaf area. FOSS NIR system can be use for nondestructive assessing nitrogen, leaf chlorophyll, carotenoids, flavonoids and anthocyanins whereas the other meters can only used for nondestructive assessing leaf nitrogen and leaf chlorophyll. These results indicate it is possible to use nondestructive spectral methods as the precision viticulture tools to manage vineyards nitrogen fertilization and grapevine performance.

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Bench-grafted Fuji/M26 apple (Malus domestica Borkh) trees were fertigated with different concentrations of nitrogen by using a modified Hoagland's solution for 45 days. CO2 assimilation and actual photosystem II (PSII) efficiency in response to incident photon flux density (PFD) were measured simultaneously in recent fully expanded leaves under low O2 (2%) and saturated CO2 (1300 ppm) conditions. A single curvilinear relationship was found between true quantum yield for CO2 assimilation and actual PSII efficiency for leaves with a wide range of leaf N content. The relationship was linear up to a quantum yield of approximately 0.05 mol CO2/mol quanta, then became curvilinear with a further rise in quantum yield in response to decreasing PFD. This relationship was subsequently used as a calibration curve to assess the rate of linear electron transport associated with rubisco and partitioning of electron flow between CO2 assimilation and photorespiration in different N leaves in response to intercellular CO2 concentration (Ci) under normal O2 conditions. Both the rate of linear electron flow, and the rate to CO2 or O2 increased with increasing leaf N at any given Ci, but the percentage of linear electron flow to CO2 assimilation remained the same regardless of leaf N content. As Ci increased, the percentage of linear electron flow to CO2 assimilation increased. In conclusion, the relationship between actual PSII efficiency and quantum yield for CO2 assimilation and the partitioning of electron flow between CO2 assimilation and photorespiration are not affected by N content in apple leaves.

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One-year-old (Old Home) OH87 and OH97 pear rootstocks were grown in 2-gallon containers under natural conditions at Corvallis, Ore., in in 1999. Uniform plants were harvested during August and September, and total leaf area, new shoot number and length, and root growth were measured. The kinetics of NH4 + and NO3 - uptake by new roots of both rootstocks were determined with the ion-depletion technique. OH87 had larger total leaf area, and more and longer shoots than OH97. Total root biomass was similiar between the two rootstocks, but OH87 had a larger proportion of new roots and more extension roots than OH97. Both rootstocks had lower Km values for NH4 + absorption than for NO3 - and therefore both had greater absorptive power for NH4 + than for NO3 - at the low nutrient concentrations. The maximum uptake rates (Vmax) of OH97 were similiar for both NH4 + and NO3 - absorption, but OH87 had a much higher maximum uptake rate for NO3 - than for NH4 +.

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`Gala'/M26 apple and `Bartlett'/OH97 pear trees growing in containers were treated with either 0, 1, 5, 10, 20, or 30g of urea dissolved in 150 mL of distilled water on 7 Sept. 1999. Two weeks after application, a soil sample from each container was analyzed for NH4 + and NO3 . One day after treatment, the leaves of the apple trees treated with either 20 or 30 g urea wilted and curled and none of the other apple treatments were affected. However, 20 days later, new lateral and terminal buds broke to grow from these two treatments. In contrast, the pear trees showed signs of wilting and leaf necrosis in the 5, 10, 20, and 30 g urea treatments about 6 days after application. Twenty days after treatment, the leaves from the two highest treatments were completely necrotic and remained attached to the trees, while the leaves of 5- and 10-g treatments were partially necrotic and began defoliating. None of the pear trees produced any new lateral or terminal growth. Soil test showed that NH4 + contents of the soils were 54.9, 104.2, 356.9, 884.28, 1154.9, and 1225.2 mg/kg for `Bartlett'/OH97, and 30.2, 62.9, 359.0, 235.1, 529.9, and 499.0 mg/kg for `Gala'/M26 and NO3 contents of the soils were 40.5, 62.4, 211.0, 129.8, 54.5, and 39.5 mg/kg for `Bartlett'/OH97, and 37.6, 42.0, 178.7, 138.2, 186.2, and 142.1 mg/kg for `Gala'/M26 treated with 0, 1, 5, 10, 20, and 30 g urea, respectively.

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Photosystem II (PSII) efficiency and CO2 assimilation in response to photon flux density (PFD) and intercellular CO2 concentration (Ci) were monitored simultaneously in leaves of apple, pear, apricot, and cherry with a combined system for measuring chlorophyll fluorescence and gas exchange. When photorespiration was minimized by low O2 (2%) and saturated CO2 (1300 ppm), a linear relationship was found between PSII efficiency and the quantum yield for CO2 assimilation with altering PFD, indicating CO2 assimilation in this case is closely linked to PSII activity. As PFD increased from 80 to 1900 μmol·m–2·s–1 under ambient CO2 (350 ppm) and O2 (21%) conditions, PSII efficiency decreased by increased nonphotochemical quenching and decreased concentration of open PSII reaction centers. The rate of linear electron transport showed a similar response to PFD as CO2 assimilation. As Ci increased from 50 to 1000 ppm under saturating PFD (1000 μmol·m–2·s–1) and ambient O2, PSII efficiency was increased initially by decreased nonphotochemical quenching and increased concentration of open PSII reaction centers and then leveled off with further a rise in Ci. CO2 assimilation reached a plateau at a higher Ci than PSII efficiency because increasing Ci diverted electron flow from O2 reduction to CO2 assimilation by depressing photorespiration. It is concluded that PSII efficiency is regulated by both nonphotochemical quenching and concentration of open PSII reaction centers in response to light and CO2 to meet the requirement for photosynthetic electron transport.

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