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Abstract
Growth retardants [ancymidol (0.1-1.0 mg·liter−1), chlormequat (0.5-500 mg·liter−1), and paclobutrazol (0.1-1.0 mg·liter−1)] reduced shoot extension, promoted root initiation, and increased root weight in apple seedlings (Malus domestica Borkh ‘York Imperial’). The induction of root formation and increase in root weight were accompanied by a considerable increase in polyamine levels. Daminozide (0.1-250.0 mg·liter−1) and dikegulac (0.25-500 mg·liter−1) also inhibited apple seedling growth; however, these compounds did not promote rooting. Chemical names used: α-cyclopropyl-α-(4-methoxyphenyl)-5-pyrimidinemethanol (ancymidol); 2-chloro-N,N,N-trimethylethanaminium chloride (chlormequat chloride); butanedioic acid mono(2,2-dimethylhydrazide) (daminozide); 2,3:4,6-bis-O-(l-methylethylidene)-α-L-xylo-2-hexulofuranosonic acid (dikegulac); β-(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl)-lH-1,2,4-triazole-l-ethanol (paclobutrazol).
Abstract
‘York Imperial’ apple trees on EM 26 rootstock were grown in large, outdoor sand cultures for 3 years. All combinations of N at 2, 4, or 8 me/1 as all NO3 or as 3/4NH4 - 1/4 NO3; Ca at 1, 8 or 16 me/1; and B at 0.05 or 0.5 ppm were supplied in solution, with other nutrients in normal supply. Levels of N and Ca and their interactions affected growth under NO3 nutrition. Growth was greatly reduced under NH4 nutrition, but was little affected by levels of N and Ca. Leaf tissues were analysed for N, P, K, Ca, Mg, Al, B, Cu, Fe, Mn, and Zn. The average, 3-year over-all effect of NH4 nutrition was to increase leaf concentration of all elements except K, Al, and Mn. Source of N altered the main effects and interactions between levels of N and Ca. B had little effect on concentration of other elements in the leaves.
Changes in water status have been associated with various stages of dormancy and freezing tolerance in woody perennials. Recent studies in apple indicate that changes in the state (bound vs. free) of bud water are strongly correlated with the end of dormancy. In this study nuclear magnetic resonance imaging (NMRI) was used to monitor changes in the state of bud water during the photoperiodic induction of endo-dormancy in Vitis riparia. Bud water status was monitored using proton relaxation times from T1 and T2 images determined at 2, 4, and 6 weeks of long (LD) or short (SD) photoperiod treatments. Bud dormancy was determined by monitoring budbreak in plants defoliated after photoperiod treatments. NMRI allowed nondestructive monitoring of changes in tissue water state. T1 and T2 maps indicated changes in the state of the water in bud and stem tissues during the 6 weeks of treatment. Differences in relaxation times for nondormant and dormancy-induced (reversible) buds were not clear. However, T2 relaxation times were lower in the dormant buds than in the nondormant buds.
Ethephon [(2-chloroethyl) phosphonic acid] is used to increase stock plant cutting productivity through increased flower and flower bud abscission and branching. However, ethylene evolution resulting from ethephon application is suspected to cause leaf abscission of unrooted cuttings during shipping. It was the objective of this study to assess ethylene evolution from ethephon-treated cuttings during storage and shipping of unrooted cuttings. Impatiens hawkeri W. Bull ‘Sonic Red’ and ‘Sonic White’ stock plants were treated with 0, 250, 500, or 1000 mg·L−1 ethephon. Cuttings were harvested from 1 to 21 days later and each harvest was stored at 20 °C in sealed jars for 24 h before ethylene measurement. Higher ethephon doses resulted in greater ethylene generation. Cuttings harvested 1 day after treatment with 0, 250, 500, or 1000 mg·L−1 ethephon evolved 0.07, 1.3, 1.7, or 5.8 μL·L−1·g−1 (fresh weight) ethylene in the first 24 h of storage at 20 °C, respectively. Twenty-one days after treatment, cuttings from the same plants evolved 0.05, 0.05, 0.15, or 0.14 μL·L−1·g−1 (fresh weight) ethylene in the first 24 h of storage at 20 °C, respectively. As cuttings were harvested from Day 1 to Day 21, ethylene concentrations evolved within the first 24 h of storage decreased exponentially. Rinsing cuttings, treated 24 h earlier with 500 mg·L−1 ethephon, by gently agitating for 10 s in deionized water reduced ethylene evolution to 0.7 μL·L−1·g−1 (fresh weight) as compared with 1.7 for unrinsed cuttings. Cuttings harvested 24 h after treatment with 500 mg·L−1 ethephon stored at 10, 15, 20, and 25 °C for 24 h evolved 0.37, 0.81, 2.03, and 3.55 μL·L−1·g−1 (fresh weight) ethylene. The resulting mean temperature coefficient (Q10) for the 10 to 25 °C range from all replications was 5.15 ± 0.85. Thus, ethylene continues to evolve from ethephon-treated Impatiens hawkeri stock plants for up to 21 days and can accumulate to high concentrations during cutting storage.
Abstract
Apple trees (Malus domestica Borkh. ‘Spartan’ grafted on MM 106 rootstock) planted in 1976 in an orchard at Beltsville, Md., were treated with paclobutrazol a gibberellin biosynthesis inhibitor, in Spring 1982 and again in 1983. In 1982, paclobutrazol [50 wettable powder (WP)] was applied as a foliage spray on 4, 14, and 25 May 1982, at 333 mgliter−1. On 27 Apr. 1983, trunks of these trees were painted with 75 g·liter−1 of paclobutrazol. Paclobutrazol did not inhibit shoot growth in 1983 but it retarded the shoot growth significantly during 1984. The carbohydrate content of paclobutrazol-treated wood was generally higher at all sampling dates from the winter dormant period through growth resumption in the spring. Negative correlation coefficients were found between starch and soluble carbohydrates in the wood during the winter sampling dates, whereas positive correlation coefficients were evident during the spring growth resumption period. The increase in carbohydrates induced by the treatment was similar in both years, when growth was not inhibited (1983) or inhibited (1984), indicated that paclobutrazol has an effect on carbohydrate metabolism as well as growth. Chemical name used: β-[(4-chlorophenyl)methyl]-α-(l,l-dimethylethyl)-1H-1,2,4-triazole-1 -ethanol (paclobutrazol).
Intact apple (Malus domestica Borkh.) buds were examined by magnetic resonance imaging (MRI). MRI did not excite water in unchilled apple buds and could not image it. When chilling was satisfied, images were produced. We interpret this difference to mean that water is in bound and/or structured form in dormant apple leaf buds before the chilling requirement is satisfied. Conversion of bound to free water occurred equally in the low-chilling-requirement cultivar Anna and the high-chillingrequirement cultivar Northern Spy only after 600 and 4000 hours of chilling, respectively. It appears that processes involved in satisfying chilling requirement are also converting water in buds from bound to free form. Absence of free water in dormant buds during the winter signifies endodormancy, whereas when the water is in free form, buds are ecodormant. Thidiazuron, a dormancy-breaking agent, applied to partially chilled buds is instrumental in converting water to the free form within 24 hours. Summer-dormant buds contain free water, and they could be classified only as paradormant. Based on proton profiles, ecodormant and paradormant buds cannot be distinguished but endodormant buds can be readily identified.
An increase in ascorbic acid, reduced form of glutathione (GSH), total glutathione, total non-protein thiol (NPSH) and non-glutathione thiol (RSH) occurred as a result of induction by thidiazuron during bud break, whereas dehydroascorbic acid and oxidized glutathione (GSSG) decreased during the same period. Thidiazuron also enhanced the ratio of GSH/GSSG, and activities of catalase, superoxide dismutase (SOD), ascorbate free radical reductase (AFR), ascorbate peroxidase (POD), dehydroascorbate reductase (DHAR), ascorbate oxidase (AAO), and glutathione reductase (GR). The ascorbic acid content and the activities of catalase, SOD, AFR, POD, AAO, and DHAR peaked when buds were in the side green or green tip stage just prior to the start of rapid expansion, and declined thereafter. The GSH, NPSH, RSH, ratio of GSH/GSSG, and activity of GR increased steadily during bud development.
Abstract
Open-pollinated ‘York Imperial’ apple (Malus domestica Borkh.) and Nemagard peach (Prunus persica (L.) Batsch) seedlings were grown in nutrient solution containing either NH4 + or NO3 -. The solution contained 0 or 4 ppm A1 and the pH was maintained at 4.5 by frequent adjustment. Apple seedlings grew better, and growth was less affected by Al, when the N source was NH4 + rather than NO3 -. Peach seedlings grew better when supplied with NO3 -. The total quantity of Ca, Mg, K, P, Zn, Cu, Mn, and Fe taken up by both apple and peach seedlings was less in the presence of Al when N was supplied as NO3 -. Nutrient uptake by seedlings receiving NH4 + was slightly less or not affected by the presence of Al. Uptake of Mn and Fe was greater in both species and K and P uptake greater in apples, whereas Ca uptake by peach seedlings was less in the presence of NH4 +. Aluminum uptake and transport was lower with NH4 + than with NO3 - as N source.
Magnetic resonance imaging estimates unreasonably high T2 times when creating T2 images in woody plants when tissues contain a limited amount of water. We developed a system to correct such images. Tissue distribution of proton density and states of water were determined by creating images of proton density and T2 relaxation times in summerdormant (paradormant) apple (Malus domestica Borkh.) buds. These images reveal that the proton density and water states obviously are not distributed uniformly in the bud and stem; but, the distribution of water depends greatly on the tissue type (bark, xylem, or meristem of the stem), and there are differences in the states of water even within the same tissue. At low proton density T2, calculated relaxation times were unreasonably high in tissues, with the exception of meristem of the shoot. In buds that were induced to grow and in which proton density was higher, T2 times appeared as expected. Variance of T2 times in tissues containing little water was 50 times higher than in those with a higher water content. Data with such high variance were excluded from the images; thus, the image was “corrected.” Corrected images of T2 times fit the distribution of water indicated by the proton density images well.
Abstract
Open pollinated ‘York Imperial’ apple seedlings (Malus domestica Borkh) were grown in an acid soil at 2 liming rates or in nutrient solution with or without added aluminum, with either NH4 + or NH3 - at various rates as N source. High and equal Ca levels were maintained for the different Al treatments. Growth of seedlings and Ca-uptake in the soil were much less at pH 4.7 than at 5.1, and seedlings responded better to liming when NH4 + was the N source. With either N source, best growth was obtained at a rate of 100 ppm N, whereas growth was lower at 50 and at 200 or 400 ppm N. In nutrient solution, the efficiency of Ca-uptake by roots and of Ca-transport was decreased by the presence of Al. This decrease was the greatest when NH3 -, rather than NH4 +, was the N source. The findings suggest interference by Al in nitrate metabolism. Al is toxic to apple seedlings at chemical activity in the order of 6.5 × 10—6M.