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Extended storage studies were conducted on papaya, Carica papaya L. `Kapoho Solo', seeds to observe the effect of KNO3 preconditioning treatment when seeds were stored under ambient (25 C) and refrigerated (10 C) temperatures for 0, 2, 6, and 12 months. KN03 treated seeds maintained a constant germination percentage of 46.7 ± 2.7% throughout the 12 month period at both storage temperatures. Non-treated seeds stored at 25 C, however, had increased germination percentages (from 11 to 40% germination) after 2 months storage. Nontreated seeds stored at 10 C displayed a slower increase in germination percentages. The beneficial effects of KNO3 preconditioning treatments over nontreated seeds is observed only when seeds are sown immediately or within 2 months of storage at 25 C.
Although the size of pot mums can be controlled with retardants, the use of such chemicals may become limited. Genetically dwarfing current cultivars may be an alternative. Using a construct including a chimeric oat phytochrome structural gene, tobacco phenotypes have been produced that strongly resemble retardant-treated plants. We wished to insert this construct in mum by using particle bombardment and determine the effects on plant size and flowering dynamics. A target system was developed using `Iridon' mum leaf sections regenerated on an IAA/BA medium. Shoots developed from surface cells principally at the cut edges. Regenerates were grown-on through flowering and no visual aberrations were apparent. Levels of 50 to 100 mg/l kanamycin were inhibitory to bud development. Sections were exposed to gene transfer and shoots recovered that appear resistant to kanamycin. Some appear chimeric while others appear to be escapes stimulated by a `feeder' effect from nearby transformed cells. Further analyses will determine whether some plants are stably transformed. (Supported by a Duffett Research Grant from Yoder Brothers, Inc.)
Abstract
Pseudomonas syringae van Hall, an ice nucleation active (INA) bacterium, increased frost susceptibility of tomato (Lycopersicon esculentum Mill.) and soybean (Glycine max L.) when sprayed on leaves prior to low temperature stress. Tomato and soybean plants inoculated with INA bacteria were nucleated and frozen at −4° and −5°C respectively. Control plants that were free of INA bacteria supercooled and survived to −8°. A threshold INA bacterial concentration of about 4 × 105 cells/ml was necessary for ice nucleation. Ice nucleating active bacteria preconditioned at 2° showed a marked increase in efficiency of ice nucleation. Preconditioned INA bacteria had ice nucleation temperatures 5° higher than INA bacteria held at 21°.
Abstract
‘Redhaven’ peaches (Prunus persica L. Batsch) were sprinkled from the end of rest, January 22, 1975, until the time check trees reached full bloom, April 18, 1975. Sprinkling delayed bloom by 15 days. Energy models predicted bloom one day before it occurred in the check trees. Wood temperatures were lowered as much as 6.5°C in sprinkled trees, but no significant difference in wood cold hardiness was observed. Sprinkled fruit buds were more cold hardy than non-sprinkled fruit buds until early March. Non-sprinkled buds were more cold hardy than sprinkled fruit buds in late March. Sprinkling reduced the number of viable buds/m by late March. Analyses of total and reducing sugars and protein showed no significant difference.
Abstract
A range of tomato (Lycopersicon esculentum Mill.) cultivars was examined for changes during ripening in firmness, endopolygalacturonase (PG) activity and the molecular forms of polygalacturonase, Ca concentration, and the extractability of the Ca. Firm cultivars were firmer than the soft cultivars throughout ripening, and generally they contained less PG activity at each stage examined. In all cultivars, PG was predominately or entirely in the high molecular weight form (PG1) early in ripening, with the PG2 forms being increasingly prominent as ripening progressed. Differences in firmness were established while PG1 was the predominant PG. Uronic acid polymers in isolated cell walls were degraded rapidly by endogenous PG when citrate was present to complex Ca. In the presence of sufficient citrate, cell wall uronic acids of a firm and soft cultivar were equally susceptible to hydrolysis, suggesting that differences in the digestion of the walls by PG were dependent upon differences in Ca content or distribution. However, neither total, water, nor saline-extractable Ca showed consistent correlations with fruit firmness, and they also showed no progressive change during ripening.
Abstract
Anatomical and morphological similarities in flower and fruit development exist among cultivars of peach and nectarine [Prunus persica (L.) Batsch ‘June Gold’, ‘Harvester’, and ‘ArmKing’] and some other members of Rosaceae. The abscission of peach and nectarine fruit involves events at 3 recognizable zones between the fruit and the stem. Of these 3 zones, the most distal is the most complex and does not form a discrete separation layer. The basal zone is predominant in samples treated with the ethylene releasing compound, CGA-15281 [(2-chloroethyl) methyl-bis (phenlymethoxy) silane]. Mature fruit from untreated plants generally abscise at the most distal zone.
The effect of increasing micronutrient levels on buffalograss (Buchloe dactyloides) was investigated. Seedling plants established in peat-lite mix in 10-cm pots were irrigated with solutions containing 0.5, 1, 2, 4, 6, 8, or 12 mM of boron (B), chloride (Cl), copper (Cu), iron (Fe), manganese (Mn), molybdenum (Mo), or zinc (Zn). The control solution contained (in μM): 20 B, 0.5 Cu, 40 Fe, 10 Mn, 0.5 Mo and 4 Zn. A standard macronutrient concentration was used for all treatment solutions. Boron and Mo induced visual toxicity symptoms more readily than other micronutrients. Boron toxicity was characterized by chlorosis often accompanied by bleached leaf tips, while Mo toxicity resulted in leaf necrosis. The lowest levels that induced foliar toxicity symptoms were: 0.5 mM B, 2 mM Cu, 4 mM Fe, 6 mM Mn, 1 mM Mo, and 4 mM Zn. Chloride did not induce foliar abnormalities in the concentration range tested. Biomass yield was reduced when the nutrient solution contained 2 mM B, 8 mM Cu, 2 mM Mo, or 12 mM Zn. Elevated levels of Cl, Fe and Mn did not alter dry matter yield. Tissue concentrations of micronutrients were also determined.
Container-grown Viburnum plicatum Thunb. var. tomentosum (Thunb.) Miq. were transplanted on May 1 into tilled plots, tilled plots amended with aged pine bark, and untilled unamended plots (control) within a greenhouse. Plants were irrigated weekly for three months prior to drought initiation. Root growth, shoot growth, leaf water status, and leaf expansion rates were measured to determine whether tilling or site amending enhanced drought stress resistance. Prior to drought initiation amended treatments had the greatest new root length. New root dry weight of amended plots was 57% greater than controls and 32% greater than tilled plots. Mean root system diameter was 111 cm, 87 cm, and 61 cm for amended, tilled, and control plots, respectively. The mean ratio of new root length (cm) to leaf area (cm2) was 5.3:1 in amended plots, 2.2:1 in tilled plots, and 1.7:1 in controls. During the drought, midday relative leaf water content was lowest in controls, while the rate of leaf expansion was greatest in tilled plots. Changes in soil moisture were monitored using time domain reflectometry. Control plots had higher volumetric water content; however, moisture release curves suggest that tilled and amended plots contained more plant available water.
Light has long been known to stimulate anthocyanin accumulation in apple peel, but changes in apple flavor as a result of fruit shading is poorly understood. Some growers maintain that the redder the strain, the less flavorful the fruit. An experiment was conducted to help characterize the role of light in biosynthesis of color versus flavor molecules in apple peel. Bags fashioned from 3 meshes of shade cloth were fastened around fruitlets of red delicious strains `Starkrimson' and `Topred' on M26, MM106, and MM111 by 21 DAFB to produce average light ranges of 100%. 41-68%, 12-30%, and < 1% of full sun incident upon the fruit. Observations from the 1993 harvest indicate that anthocyanin content of peel increased with fruit maturity and level of sunlight. Concentrations of flavor molecules were higher with low and moderate shade than with full sun, and also increased with fruit maturity. From this harvest data, it appears that apple flavor can be enhanced by lightly shading fruit without substantially reducing fruit color.
Despite efforts to optimize water and nutrient inputs to Florida's vegetable and fruit crops, the sandy soils, shallow water table, and tropical climate of Florida result in nutrient leaching losses that are unavoidable. Water quantity and quality management strategies that can reduce these nutrient losses from Florida's horticultural crops were reviewed and research needs for quantifying their effectiveness were identified. The water quantity management strategies included water table management for irrigation, drainage management, detention of runoff and drainage, and summer flooding. In addition to the expected water quality benefits of these practices, potential effects on crop production and farm economics were also discussed. Watershed-scale adoption of stormwater harvesting has the potential to not only reduce the nutrient loadings but also become a source of additional income for landowners through water trading. The water quality practices included structural and managerial practices (e.g., vegetative filter strips and ditch cleaning). Key research needs for reducing the unavoidable nutrient discharges included the development of a crop-specific drainage management tool; quantification of farm and watershed-scale benefits of stormwater detention and its reuse with regards to nutrient loadings, water supply, crop production, and farm income; enhancement of hydraulic efficiency of detention areas; and effects of summer flooding and ditch maintenance and cleaning on nutrient discharges.