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Sergio Tombesi, Bruce D. Lampinen, Samuel Metcalf, and Theodore M. DeJong

in almond trees), flower induction is related to the spur leaf area in the previous year and fruit bearing decreases the probability that a spur can bear flowers in the next year in comparison with spurs with similar leaf area that did not bear fruits

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Cheryl R. Hampson, Harvey A. Quamme, Frank Kappel, and Robert T. Brownlee

The effect of increasing planting density at constant rectangularity on the vegetative growth and light interception of apple [Malus ×sylvestris (L) var. domestica (Borkh.) Mansf.] trees in three training systems (slender spindle, tall spindle, and Geneva Y trellis) was assessed for 10 years. Five tree densities (from 1125 to 3226 trees/ha) and two cultivars (Royal Gala and Summerland McIntosh) were tested in a fully guarded split-split plot design. Planting density was the most influential factor. As tree density increased, tree size decreased, and leaf area index and light interception increased. A planting density between 1800 and 2200 trees/ha (depending on training system) was needed to achieve at least 50% light interception under the conditions of this trial. Training system altered tree height and canopy diameter, but not total scion weight. Training system began to influence light interception in the sixth leaf, when the Y trellis system intercepted more light than either spindle form. Trees trained to the Y trellis tended to have more spurs and a lower proportion of total leaf area in shoot leaves than the other two systems. The slender and tall spindles were similar in most aspects of performance. Tall spindles did not intercept more light than slender spindles. `Royal Gala' and `Summerland McIntosh' trees intercepted about the same amount of light. `Royal Gala' had greater spur leaf area per tree than `Summerland McIntosh', but the cultivars were similar in shoot leaf area per tree and spur density.

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Bruce H. Barritt and Bonnie J. Schonberg

Vegetative (nonflowering) spur characteristics of `Granny Smith', `Lawspur Rome', and `Redchief Delicious' apples (Malus domestics Borkh.) at two canopy positions (1 and 2 m heights) were examined on eight dates throughout a growing season. `Granny Smith' had a greater leaf number/spur (LNO/SP) at each date than `Rome' and `Delicious'. Area/leaf (LA) and dry weight/leaf (LDW) for `Delicious' were substantially less than for `Granny Smith' and `Rome'. Area/leaf increased rapidly after full bloom (FB) until FB + 21 days for `Delicious', FB + 35 for `Granny Smith', and FB + 56 for `Rome', after which no further changes occurred. For each cultivar, leaf area/spur (LAMP) and leaf dry weight/spur (LDW/SP) increased rapidly from FB until FB + 35 days and then more gradually until FB + 104 days. From FB + 21 onward, `Granny Smith' had greater LA/SP and LDW/SP than `Rome', which, in turn, was greater than for `Delicious'. At harvest (FB + 160), LA/SP was 2.5-fold greater for `Granny Smith' and 1.7-fold greater for `Rome' than for `Delicious'. Cultivar differences for leaf dry weight/leaf area (LDW/LA) were small and canopy position differences were large. LDW/LA declined from 7 days before FB to FB + 7, then gradually increased to the end of the season. Dry weight of the vegetative spur buds (with leaves removed) was lower for `Delicious' than for `Rome' or `Granny Smith'. Total spur dry weight (bud + leaves) was, from FB + 21 onward, greatest for `Granny Smith', intermediate for `Rome', and lowest for `Delicious'.

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James R. Schupp, H. Edwin Winzeler, Thomas M. Kon, Richard P. Marini, Tara A. Baugher, Lynn F. Kime, and Melanie A. Schupp

shoots, producing a higher number of spurs per unit limb size, with more spur leaves, higher spur leaf area, and greater values for the ratio of spur leaf area to shoot leaf area ( Table 3 ). Lakso (1984) also found that “moderately” pruned ‘Empire

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Thomas M. Kon, James R. Schupp, H. Edwin Winzeler, and Richard P. Marini

before anthesis and can be damaged by physical disturbance. Ferree and Palmer (1982) showed the importance of spur leaf area on young fruit development and retention. As illustrated by Ngugi and Schupp (2009) , mechanical thinners can also be an

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Richard J. Heerema*, Ted M. De Jong, and Steven A. Weinbaum

Spurs are the primary bearing unit in mature `Nonpareil' almond (Prunus dulcis (Mill.) D.A. Webb) trees. Our objective was to determine whether almond spurs behave autonomously with respect to various biological activities throughout the season. If autonomous, a spur's carbohydrate demands are met primarily by its own leaves and, therefore, the sink to source ratio of the spur itself is expected to be closely linked to its growth and development. In these experiments almond spurs differing in leaf area and/or fruit number were monitored for leaf development, fruit set, floral initiation, spur survival and carbohydrate storage. Previous-season spur leaf area had no relation to the number of leaves preformed within the dormant vegetative bud or final spur leaf area in the current season, but spurs which fruited in the previous season began spring leaf expansion later and current-season spur fruiting was associated with lower spur leaf area. There was little or no relationship between final percentage fruit set at the spur level and spur leaf area in either the current or previous seasons. Current-season spur leaf area was positively related to both spur flower bud number and spur winter survival. Carbohydrate storage in dormant spurs increased with increasing previous-season spur leaf area. These data are consistent with the concept of spur autonomy especially with regards to spur activities late in the season. The relationships of some of these same spur parameters to spur light exposure are currently being investigated.

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Guohai Xia, Lailiang Cheng, Alan Lakso, and Martin Goffinet

supply ( Fig. 2 ). The total leaf area of an apple tree consists of two types of leaf area: spur leaf area and shoot leaf area. Increasing N supply did not significantly affect total spur leaf area but increased total shoot leaf area ( Fig. 2 ). Fig

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Terence L. Robinson and Zhongbo Ren

Eleven year-old Empire/M.7 apple trees were shaded continously for 4 years with half-tree shading cages. Shading reduced primary spur leaf duration, bourse shoot leaf area, specific leaf weight, spur diameter and bud diameter. Over the four years, shaded spurs continued to increase in length but spur diameter increased very little resulting in long and brittle spurs. However, shaded spurs continued to flower and set fruit. Leaf area development was similar inside and outside the cages at one week after bloom but by 2 weeks after bloom, spurs inside the cages had significantly lower leaf area. Shading reduced fruit set, fruit size, fruit color, fruit soluble solids and fruit dry matter. Fruit growth rate was reduced by shading early in the season but was no different than the unshaded controls by 4 weeks after full bloom.

In an attempt to reverse the negative effects of shading on spur vigor, foliar urea, zinc-EDTA and solubor were sprayed 3 times during the early growing season each year. Rather than increasing spur leaf area, foliar nutrient sprays significantly reduced bourse shoot leaf area and did not increase the duration of primary spur leaves. Although foliar nutrients reduced total spur leaf area, they improved fruit size, color and soluble solids slightly.

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Ian J. Warrington, David C. Ferree, James R. Schupp, Frank G. Dennis Jr., and Tara A. Baugher

The characteristics of 1-year-old vegetative spurs growing on 2-year-old branches were measured on 28 `Delicious' apple (Malus domestica Borkh.) strains growing on M.7 rootstocks at Clarksville, Mich., and on 23 strains of `Delicious' on M.7a rootstocks at Kearneysville, W.Va. Spur-type strains typically had densities >20 to 21 spurs/m, and high spur leaf numbers, leaf areas per spur, leaf areas per leaf, and terminal bud diameters, whereas values for standard strains were generally lower. However, for most spur quality characteristics, there was a continuous range of values between the extremes rather than any distinct grouping into either spur or standard type. At both sites, spur density was significantly and positively correlated with yield efficiency. In a related study, the spur characteristics of `Starkspur Supreme' were measured on nine rootstocks: M.7 EMLA, M.9 EMLA, M.26 EMLA, M.27 EMLA, M.9, MAC 9, MAC 24, OAR 1, and Ottawa 3. Spur leaf number and spur leaf area were both high with vigorous rootstocks, whereas spur density was low. The rootstocks MAC 9, M.9, and M.9 EMLA had the highest yield efficiencies.

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Renae E. Moran and Curt R. Rom

The relationship of variability in flowering and fruiting habit to canopy position and changing diurnal light and photosynthetic pattern was examined in 7 mature spur-type `Red Delicious'/MM106 apple trees. A .5×.5m column was placed in the north, south, east and west sections of tree canopies. Columns were subdivided by height with 3 study areas located at .25-.5m, 1.0-1.25m and 1.75-2.0m from the top of the canopy. In each, section, flowering index, fruit set, individual fruit weight and size, skin coloration, fruit soluble solids content, spur leaf area and spur bud diameter were determined. Photosynthetically active radiation and photosynthesis were measured from bloom through harvest correlated with variability in flowering, fruiting, spur quality and distribution of growth.