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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.
Proton Density and T2 maps were created throughout the dormant season in `Anna' and Northern Spy′ apple cultlvars. The percentige of oixels with 15-25 ms T2 time increased from 30% in both cultlvars at the beginning of dormancy to 80 and 72% respectively, by the end of dormancy. The conversion in `Anna' was rapid and in `Northern spy was slow. Growth occured only when conversion of bound to free water reached 70% of the total number of pixels. Buds entered into a transitional phase when conversion of water reached 50%. Buds in the transitional phase are willing to respond to treatments aimed to end dormancy. Thus dormancy can be divided into two major part based on the boundness of freeness of water in the bud.
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).
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
A cyanide-resistant alternative pathway was found to exist in root tissue of apple (Malus domestica Borkh.). In the absence of potassium cyanide (KCN), an inhibitor of cytochrome electron transport, the alternative pathway did not contribute to overall root respiration. However, in the presence of KCN or carbonyl cyanide m-chlorophenyl hydrazone (CCCP), an uncoupler, active participation of the alternative pathway was detected. Inhibition of O2 uptake by salicylhydroxamic acid (SHAM) was observed in the presence of antimycin A (AA) or sodium azide (NaN3), but to a lesser degree than when KCN was present. The degree of inhibition by SHAM was greatest in the presence of KCN, followed by AA and then NaN3. The antioxidant n-Propyl gallate (PG) was found to be an effective inhibitor of the alternative pathway. The site of inhibition in apple root tissue by PG is very similar to that of SHAM. Sodium benzoate, another antioxidant and free radical scavenger, and tetraethylthiuram disulfide (disulfiram), a copper chelator, did not inhibit the alternative pathway in apple root tissue.
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
Polyethylene glycol (PEG-4000)-induced water stress (—0.5 to —7.5 bars) reduced shoot and root growth, water use, and stem 45Ca in seedlings of peach (Prunus persica (L.) Batsch). Sucrose feeding through a leaf did not affect stem 45Ca with or without osmotic stress. 45Calcium uptake per milligram water used was not different at different solution osmotic potentials. A split-root study, with half the root system receiving 45Ca and/or PEG, showed that if 45Ca was supplied only to the water-stressed root half, 45Ca uptake into stems was low regardless of whether the other root half was stressed or not. Results indicate that reduced stem Ca during water stress is probably not a direct result of decreased root energy needed for active uptake or reduced translocation out of the root. Calcium absorption appeared to be related to the amount of unsuberized root surface available for Ca uptake.