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Abstract
‘Nemaguard’ peach seedlings [Prunus persica (L.) Batsch] were grown in nutrient solution cultures containing 0.36 µM 14C-labeled paclobutrazol (0.59 MBq·liter–1) for 9 days. Microautoradiographs of transverse and longitudinal stem sections showed that 14C activity was localized in the xylem. Tissue extracts showed that the total 14C activity in the plants was distributed predominantly between the roots (40.9%) and leaves (49.1%). The majority of 14C activity in stems and leaves was located in the lowest stem and leaf fractions. The concentration of 14C activity was highest in leaves (478 dpm·mg–1 fresh weight), and essentially equal in the roots and stems (141 dpm·mg–1 fresh weight) indicating that transport of the compound was occurring via the xylem. Although 14C-labeled paclobutrazol was relatively stable in the nutrient solution, its degradation in the plant was rapid. By 9 days after treatment, the amount of 14C label remaining as 14C-labeled paclobutrazol was 71.5% in the roots, 41.5% to 68.1% in the stems, and 7.8% to 12.2% in the leaves. Chemical name used: β-(4-chlorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
Abstract
‘Nemaguard’ peach seedlings [Prunus persica (L.) Batsch] were grown for 21 days in nutrient solution cultures containing a range (0 to 3.4 μM) of paclobutrazol concentrations. Shoot growth rate and total extension growth were reduced by all paclobutrazol treatments. Within 2 days of treatment, paclobutrazol at 3.4 μM significantly reduced the growth rate, as did the 3.4 × 10−2 μM concentrations after 5 days. Increases in paclobutrazol concentrations decreased leaf area and leaf, stem, and shoot weights. However, specific leaf weight increased as paclobutrazol concentration increased. Leaf expansion was more sensitive to paclobutrazol treatments than stem elongation. As paclobutrazol concentration increased, root extension growth was reduced, but roots were thicker and produced more laterals near the tip. Compared with the control, paclobutrazol at 3.4 × 10−1 and 3.4 × 10−2 μM significantly increased the root: shoot ratio. Chemical name used: β-[(4-chIorophenyl)methyl]-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-1-ethanol (paclobutrazol).
Photoperiod is an important environmental signal for regulating developmental patterns in many plant species. In several species, photoperiodic regulation of gibberellin A1 biosynthesis has been implicated as the mechanism by which photoperiod may alter development. To examine this phenomenon in strawberry, Fragaria virginiana plants grown under long day (LD) and short day (SD) conditions with equivalent total PAR were examined to determine changes in vegetative growth and GA1 biosynthesis.
LD conditions (16 hr) promoted vegetative growth. Runner production, total leaf area, area of individual leaves, and petiole lengths, all increased under LD conditions. No runner production occurred under SD conditions (8 hr); however, the number of branch crowns increased.
Gibberellins A44, A19, A20, and A1, all from the GA1 biosynthetic pathway, were identified in plants under both LD and SD conditions. However, SD conditions appeared to affect the 2β-hydroxylation of GA20 to GA1. Whereas levels of most GAs decreased under SD conditions, levels of GA20 increased, and only trace amounts of GA1 were found, indicating a possible blockage of the pathway at this point. As GA1 is considered the active component of the pathway, blockage of GA20 conversion under SD conditions may explain the concomitant reduction in vegetative growth.
Abstract
The influence of 3 spacings, 4 rootstocks, and 2 cultivars of apple (Malus domestica Borkh.) on yield, fruit and tree size and mineral composition of leaves during the 3rd through the 6th year of growth in the orchard were investigated. Scion cultivar had the greatest effect on mineral composition; all elements except manganese were significantly different in the 2 spur-type cultivars (‘Goldenspur’ and ‘Redspur’). Trees on Mailing Merton (MM) 106 rootstock produced larger yields than those on other rootstocks, and the foliage was usually among the highest in respect to each nutrient measured. Closely spaced trees had smaller fruit and the least amount of foliar P and K but Ca, Mg, and Mn were high in the same trees.
Olive (Olea europaea L.) field experiments involving natural flower and fruit populations are fraught with variability, resulting in large coefficients of variation. We provide evidence that coefficients of variation can be reduced successfully by judiciously selecting four experimental twigs per tree and using only those twigs with an internodal growth ≥2 cm, two inflorescences per node, and that are selected from trees with near-maximum bloom density. Although counting flowers at full bloom may establish the population uniformity, only a single node; e.g., node 5, is needed for analysis. Increasing the number of trees will reduce variance more than increasing the number of twigs or nodes.
Abstract
‘Redhaven’ peach on 5 seedling rootstocks planted in the spring of 1973 in a water-logged soil exhibited varying degrees of injury by July. ‘Rutgers Red Leaf’ was most tolerant; ‘Lovell’ was least tolerant. These differences suggest the feasibility of breeding for “wet feet” resistance in peach rootstocks.
Abstract
Total immersion of Pseuderanthemum atropurpureum L. H. Bailey, Sanchezia speciosa J. Leonard, and Strobilanthes dyeranus M. T. Mast. cuttings in aqueous solutions of the morphactins chlorflurecol and chlorflurenethol prior to propagation retarded plant growth 16 weeks after rooting. Height of Sanchezia and Strobilanthes also was reduced by dips of chlorfluren and dichlorflurecol and chlormequat chloride. Morphactins caused abnormal growth on Pseuderanthemum and Strobilanthes. Dips of PBA reduced the height of Pseuderanthemum and Strobilanthes. Pseuderanthemum height also was reduced by ancymidol and ethephon dips, and height was reduced on Strobilanthes by oxathiin and piproctanyl bromide. Chlorflurecol dips reduced plant dry weight of all species. Plant dry weight of Strobilanthes also was reduced by chlorofluren, chloroflurenthol, oxathiin, and PBA immersion. Ethephon, PBA, and chlorflurenthol dips also reduced Pseuderanthemum dry weight. Chemical names used: 2-chloro-9-hydroxy-9H-fluorene-9-carboxylic acid (chlorflurecol); 2-chlorofluorenecarbonic acid-(9)-methylester (dichloroflurecol); 2-chloro-9-hydroxyfluorene-carbonic acid-(9)-p-chlorophenoxyethylester (chloroflurenethol); 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride); N-(phenylmethyl)-9-(tetrahydro-2H-pyran-2-yl)-9H purin-6-amine (PBA); α-cyclopropyl-α-(4-methoxyphenyI)-5-pyrimidinemethanol (ancymidol); (2-chlorethyl)phosphonic acid (ethephon); 2,3-dihydro-5,6-diphenyl-1,4-oxathiin (oxathiin); 1-(3,7-dimethyloctyl)-1-(2-propenyl)piperidinium bromide, (piproctanyl bromide).
Exudation of organic acids by roots has been implicated in uptake of minerals from soil. Three cultivars within each of two subspecies of summer squash (Cucurbita pepo ssp. ovifera D. S. Decker var. ovifera and C. pepo ssp. pepo var. pepo) were grown in the field. Plants of ssp. pepo had higher concentrations of K, P, and Zn than those of ssp. ovifera. These same cultivars were grown under P sufficient and depleted conditions in hydroponics, to measure exudation of organic acids from roots. When grown in hydroponics, tissues of ssp. ovifera had similar or higher concentrations of nutrients than ssp. pepo. Therefore, differences in tissue composition of field-grown plants are likely due to differences in nutrient uptake ability, not inherent differences in tissue composition between subspecies. Phosphorus nutrition played a significant role in exudation of organic acids into the hydroponics solution. For both subspecies, P depletion resulted in exudation of more citric and succinic acid, and less oxalic and tartaric acid. Under P depletion, ssp. pepo exuded more citric acid than ssp. ovifera. When soil was eluted with solution containing root exudates, the exudates from ssp. pepo eluted more K, Mg, Fe, and Zn than did those from ssp. ovifera. Among subspecies of C. pepo, exudation of organic acids, particularly exudation of citric acid in response to P depletion, is associated with the plant's ability to accumulate more inorganic nutrients when grown in the field.
Isothermal microcalorimetric measurements of metabolic heat rates of `Kerman' pistachio (Pistacia vera L.) individual inflorescence buds, current-year and 1-year-old shoots were used to investigate the roles of current and reserve photosynthates in the abscission of inflorescence buds. In the early stages of development metabolic heat rates of individual inflorescence buds were two and three times those of individual current-year and 1-year-old shoots respectively. Individual shoot organs (1-year-old shoots, current-year shoots, and inflorescence buds) sampled from “on” trees had higher metabolic heat rates than similar individual organs sampled from “off” trees. Artificial shading of pistachio trees for 14 days in early June depressed metabolic heat rates of individual inflorescence buds within 24 h, but there was a delay of 4 days before the decline in metabolic heat rates of individual current-year and 1-year-old shoots. This suggests that metabolic heat rates of individual inflorescence buds apparently depended on currently fixed photosynthates.
Abstract
The transpiration rate of potted oleanders (Nerium oleander L.) in a greenhouse was reduced 25-35% for 2 weeks after being sprayed with a film-forming antitranspirant. Measurements of moisture changes in a heterogeneous soil in the median strip of a major freeway indicated that the antitranspirant slowed the depletion of soil water. This was confirmed when detailed measurement of moisture in a more uniform field soil showed a 40% reduction in water use by oleanders. These studies suggest that an antitranspirant could delay irrigation of highway oleander plantings by at least 2 weeks, reducing the costs and hazards associated with irrigation of ornamental plantings along highways.