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- Author or Editor: David Buchanan x
The synthetic triazole derivative 14C-labeled BAS111 (14C-BAS111) was readily translocated throughout 8-week-old apple seedlings (Malus domestica Borkh.) within 3 days of application to roots in hydroponic nutrient solution. The majority of labeled BAS111 and total 14C activity was recovered from middle leaves and root tissues. Two metabolites of labeled BAS111 were found. Both 14C-BAS111 and metabolite 1 were recovered predominantly from leaf and root tissue and from nutrient solution. Metabolite 2, however, was found almost exclusively in root tissue. The rapid degradation of 14C-BAS111 accounts for its low efficacy in comparison with other triazole growth retardants. Chemical name used: [1-phenoxy-5,5-dimethyl-3-(1,2,4-triazol-1yl)-hexan-4-ol] (BAS111).
β-[(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1 H-1,2,4-triazole-1-ethanol (paclobutrazol) is one of a new class of plant growth regulators that affect both vegetative and reproductive components of fruit tree growth (1-3). The movement and fate of absorbed paclobutrazol must be established to better understand its persistence and mode of action. Accordingly, we have developed an analytical method for quantifying low levels of paclobutrazol extracted from plant tissue.
Electrolyte leakage was used to measure direct heat injury to roots of Illicium anisatum L., Ilex cornuta L. cv. Burfordii and Juniperus chinensis L. cv. Parsonii. A sigmoidal relationship was found between percent electrolyte leakage and temperature treatment. About 50% electrolyte leakage was realized from a 20 minute exposure of roots to 50.5 ± 0.5°, 48.5 ± 0.5° and 46.5 ± 0.5°C for I. anisatum, J. chinensis, and I. cornuta, respectively.
Potted apple trees were severely (S) or moderately (M) droughted and compared to a well-watered control (C) to determine changes in biogenesis of leaf volatile compounds. Total available water (TAW) of the soil was allowed to decline to near 0% TAW, 20% TAW, and 100% TAW, for S, M and C, respectively, by the end of a two-week drying period. Twenty-nine volatile compounds were identified by GC-MS using headspace sampling of detached leaves. Concentrations of (E)-2-hexenal, (E)-2-hexenyl acetate, l-hexanol, (E)-2-hexen-1-ol and hexyl acetate were 5 to 310 times higher for S than C. It is suggested that the large drought induced increase in C-6 compounds was related to enhanced lipoxygenase activity.
Sweet cherry ripening is slowed during low oxygen and/or high carbon dioxide controlled atmosphere storage. Cherry flavor can be impacted by prolonged CA storage, therefore ripening after CA and storage was evaluated including production of fruit volatile compounds. `Bing' sweet cherries were harvested at commercial maturity and stored for up to 12 weeks at 1C in air or 5% O2, with 0.1, 10, 15 or 20% CO2. Fruit quality and condition were evaluated after removal from storage plus 1 or 4 days at 20C. Changes in fruit color were slow ed by all atmosphere treatments with differences most notable after longer storage durations. Volatile synthesis changed as storage duration increased, however, treatment differences were not significant. Soluble solids content was maintained at 15 and 20% CO2, but treatment differences were significant only after longer storage durations. High CO, treatments were effective at reducing decay incidence, but residual suppression after removal from storage decreased as storage duration increased. Significant treatment effects were evident for titratable acidity retention after 8 and 12 weeks storage, however, titratable acidity significantly declined in all treatments compared to the initial concentration.
Pre-climacteric `Gala' apple fruit treated with air (control) or 2 μmol·L–1 1-methylcyclopropene (MCP) were exposed to gamma irradiation at 0, 0.5, 1, or 1.5 kGy at 23 °C. Fruit were held at 20 °C for 3 weeks after treatment during which respiration rate, production of ethylene and other volatile compounds, fruit firmness, soluble solid content, titratable acidity, and irradiation injury were determined. MCP treatment reduced respiration and ethylene production and slowed loss of fruit firmness and titratable acidity. Irradiation induced increased respiration of MCP-treated fruit in a dosage-dependent fashion. Irradiation caused a decrease in ethylene production by control (non-MCP) fruit, and the magnitude of the decrease was dependent on irradiation dosage. Irradiation at 0.5, 1, and 1.5 kGy stimulated ethylene production of MCP-treated fruit for only 1 day after treatment. Irradiation induced internal browning and the injury severity increased with dosage. The severity and incidence of irradiation damage were higher in MCP-treated fruit than control fruit. The results indicate that ethylene is involved in mediating apple fruit responses to irradiation.
The influence of root temperature on whole-plant water relations and cold hardiness in seedlings of 2 citrus rootstocks—rough lemon (Citrus jambhiri Lush.) and Carrizo citrange [C. sinensis (L.) Osbeck × Poncirus trifoliata (L.) Raf.]—and ‘Valencia’ scions on both rootstocks was examined. Plants were exposed to root temperatures of 5°, 10°, or 15°C for 5–8 weeks, while shoots were exposed to a nonacclimating air temperature of 30°. Root temperatures of 5° decreased leaf xylem water potential and increased cold hardiness. Statistical differences in diffusive resistance and transpiration were observed only at the 5° root temperature. Root temperature did not significantly alter leaf relative water content in either seedlings or budded plants. A decrease in soil and root temperature alone, without a simultaneous reduction in air temperature, can provide an effective cold-acclimating environment for citrus.
‘Orlando’ tangelo (Citrus reticulata Blanco × Citrus paradisi Macf.) trees not irrigated in the fall, but protected by under-tree sprinkling during a frost, sustained the lowest percentage of leaf and fruit damage as determined 6 weeks after the frost. Trees irrigated both in the fall and during a frost, or those receiving no fall irrigation or under-tree sprinkling, were intermediate in fruit damage. Fall irrigation without sprinkling the night of a frost contributed to the most severe damage to leaves and fruit. Soil moisture content of irrigated blocks was significantly greater than for non-irrigated blocks during the fall, yet afternoon leaf xylem water potential and stem water content were comparable. Leaf freezing point of detached leaves of ‘Orlando’ and navel orange (Citrus sinensis (L.) Osbeck) was poorly correlated with leaf xylem water potential, abaxial diffusion resistance, and relative water content. Leaf freezing and killing temperature was unaffected by fall irrigation and ranged from -5.8 to -6.8°C from October until December in 1978 and 1979.
Roots of sour orange (Citrus aurantium L.), ‘Carrizo’ citrange [C. sinensis L. (Osbeck.) × Poncirus trifoliata L. (Raf.)] and ‘Swingle’ citrumelo [C. paradisi Macf. × P. trifoliata L. (Raf.)] seedlings were exposed to various high temperatures for 20 minutes and heat injury was determined by electrolyte leakage procedures, microscopic examination, and visual observations. Temperatures at the midpoint of sigmoidal curves fitted through electrolyte leakage data for excised roots were 51.6° ± 0.5°C, 52.5° ± 0.7°, and 53.5° ± 0.5° for ‘Carrizo’ citrange, sour orange, and ‘Swingle’ citrumelo rootstocks, respectively. Electrolyte leakage results with excised roots were supported by microscopic examination and visual observations of whole plants.
Mexican avocado seedlings and grafted ‘Irwin’ mangos grown under soil temperatures of 21, 27 and 32°C responded differently. The soil temperature statistically influenced the growth of the avocado seedlings but not the mangos. A soil temperature range of 21 to 27° was best for the growth of the avocado seedlings but temperatures greater than 27° reduced growth. The number of growth flushes was greater at 27° than either 21 or 32°. The avocado seedlings were tall and upright at 21° and were short and spreading at 32°.
The mineral composition of both the avocado and the mango leaves changed with soil temperatures. The content of N and P in avocado and mango leaves was highest at 32° and lowest at 27°. The K content of the avocado leaves increased with temperature, but the Fe and Zn content decreased. In the mango Mg and Fe content was highest at 27° and lowest at 21°. Calcium content of the mango leaves decreased with soil temperature.