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  • Author or Editor: Eric Young x
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During natural leaf abscission, two-year-old, potted apple trees (Malus domestica cv. MM.111 EMLA) were placed in a cold room at 6C for chilling. At 0, 600, 900, and 1400 chilling hours (CH), ten trees were removed and terminal shoots cut into four 15 cm sections. These sections were randomly placed in forty 10 1 test tubes at 20C and subjected to ten oxygen levels from 0.5 to 21% O2 with four reps each by flushing tubes with mixtures of air and nitrogen prior to sealing. Tubes remained sealed for 4 hr then reflushed and resealed for another 4 hr after which 1 ml gas samples were drawn and CO2 and O2 levels measured on a gas chromatograph. Respiration decreased with oxygen level at all CH. CO2 evolved did not show a pattern related to oxygen level, but O2 consumed decreased at a decreasing rate with additional CH. Respiratory quotient was below one at 0 and 600 CH and equal to one at 900 and 1400 CH, indicating a possible shift in respiration substrate with chilling.

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During natural leaf abscission, 2-year-old potted apple trees (Malus domestica Borkh. cv. MM.111 EMLA) were placed in a room at 6C for chilling [0,600, 900, or 1400 chilling units (CU)]. After each chilling treatment, respiration of shoot segments was measured as CO2 evolved and O2 consumed at 22C in several O2 concentrations. Respiration increased with oxygen concentration after all CU treatments. Carbon dioxide evolved at the several O2 levels did not show a pattern related to CU, but O2 consumed decreased at a decreasing rate with additional CU. Respiratory quotient was <1 at 0 and 600 CU and equal to 1 at 900 and 1400 CU, indicating a possible shift in respiratory substrate with chilling.

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Budbreak and root and shoot extension growth of apple trees (Malus domestics Borkh. MM.111) were affected by exposure to 500 hours of higher temperatures (15, 20, or 30C) during the first, second, or third 500 hours of a 1500-hour, 5C chilling period. Exposure to 15C during the third 500 hours had a significantly positive effect on budbreak, 20C at this time had no effect, and all other treatments had a negative effect on budbreak and new root and shoot growth.

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Dormant apple trees (Malus domestics Borkh., cv. MM. 111) were chilled at SC for O, 500, 1000, or 1500 hours and then forced at 10, 20, or 30C for 21 days. Budbreak and root growth were recorded after forcing, and shoot and root respiration was measured at 5, 10, 20, and 30C to determine Q10 and energy of activation values. Budbreak, root growth, and respiration generally increased with chilling and forcing temperature. The Q10 of shoot respiration increased significantly with increasing chilling when measured before forcing; however, after forcing, Q10 decreased with chilling. Root respiration Q10 was not as influenced as shoot respiration by chilling either before or after forcing. Energy of activation for shoot and root respiration decreased significantly with chilling after forcing at each temperature.

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Abstract

Seedlings of Halford and Siberian C rootstocks of peach (Prunus persica (L.) Batsch) were subjected for 3 months to 3 soil temperatures, 10°, 20°, and 30°C. The height and root and shoot dry weights of Halford seedlings were less at 10° and 30° than at 20°. Siberian C height and dry weights were reduced only by 30°; however the mortality rate was 50% at 10°. Stem caliper was unaffected by soil temperature in either rootstock. Foliage N content was low in the 10° and high in the 30° treatment, while Fe content was low in both 10° and 30°.

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Abstract

Fall- and spring-planted spur ‘Delicious’ trees were monitored for first-year spur and shoot development and major carbohydrate levels in 1986 and 1987. Fall planting resulted in significantly greater shoot extension growth and lower tendency to become spurbound than spring planting during both years for two strains of spur ‘Delicious’. Higher starch reserves were found following the growing season after fall planting than after spring planting. A root dip of 10,000 mg a.i. IBA/liter before spring planting in 1987 did not affect any of the characteristics measured. Chemical name used: lH-indole-3-butyric acid (IBA).

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Abstract

Washed and unwashed apple leaves from North Carolina orchards were sampled for 4 years. Na and Cu concentrations were higher in washed samples due to contamination from the detergent and tape water, respectively. Fe, Mn, and Zn concentrations were higher in unwashed samples due to fungicide spray deposition on the leaves. Concentrations of these elements in washed samples increased with increasing numbers of sprays of Ferbam (76 WP), Dikar (76.6 WP), and metiram (Polyram 80 WP), respectively, indicating absorption of these elements. Concentrations of N, P, K, Ca, Mg, and B were unaffected by washing.

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Abstract

Nonchilled, nursery-grown apple (Malus domestica Borkh.) trees were subjected to all combinations of root and/or shoot chilling (5°C) or nonchilling (16°) temperatures for 1500 hr. Trees then were given one of the following six plant growth regulator treatments prior to greenhouse forcing for 30 days: no plant growth regulator; 10-sec shoot dip of either 6-BA, GA4+7, or Promalin; 10-sec root dip of IBA; or IBA on root plus Promalin on shoot. Chilling either the root or shoot alone resulted in partial budbreak, while chilling the entire tree increased budbreak and dry weight of new shoots significantly. New root growth depended primarily on chilling the root. Treatment of the shoot with 6-BA, GA4+7, or Promalin increased budbreak and replaced the requirement for root chilling for this response, but did not affect new shoot dry weight or root growth. Treating the root with IBA significantly increased new root growth, budbreak, and new shoot dry weight, and replaced the requirement for root chilling for these responses. Chemical names used: N-(phenylmethyl)-1H-purin-6-amine (BA); gibberellic acid (GA4+7); 1H-indole-3-butanoic acid (IBA); mixture of BA and GA4+7 (Promalin).

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Abstract

Effects of continuous root temperatures > 15°C on vegetative budbreak, shoot and spur development, and flowering were studied during the first 3 years of growth in ‘Delicious’ apple trees (Malus domestica Borkh.) on MM.106, M.7a, and M.9 rootstocks. Sixteen trees of each rootstock-scion combination were potted and placed on an outside container area with overhead irrigation. Root-zone temperature was maintained at > 15° throughout the winter in half the trees, while the other half were at ambient temperature. Vegetative budbreak and spur development were reduced significantly and flowering was increased during the first 2 years by warm winter root temperatures. Flowering the third year was increased on MM.106 trees due to enhanced spur development the first 2 years. Flower bud to vegetative bud ratio was reduced on ambient-root trees in the second and third year and root : shoot ratio was increased, indicating that root chilling during dormancy favored vegetative growth, particularly root growth.

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