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P. Inglese, G. Barbera, and T. La Mantia

Flowers and stems (cladodes) of cactus pear [Opuntia ficus-indica (L.) Mill.] appear simultaneously in spring, and a second vegetative and reproductive flush can be obtained in early summer by completely removing flowers and cladodes of the spring flush at bloom time. The seasonal growth patterns of cactus pear fruits and cladodes were examined in terms of dry-weight accumulation and cladode extension (surface area) to determine if cladodes are competitive sinks during fruit development. Thermal time was calculated in terms of growing degree hours (GDH) accumulated from bud burst until fruit harvest. Fruits of the spring flush had a 25% lower dry weight and a shorter development period than the summer flush fruits, and, particularly, a shorter duration and a lower growth rate at the stage when most of the core development occurred. The duration of the fruit development period was better explained in terms of thermal rather than chronological time. The number of days required to reach commercial harvest maturity changed with the time of bud burst, but the thermal time (40 × 103 GDH) did not. Newly developing cladodes may become competitive sinks for resource allocation during most of fruit growth, as indicated by the cladode's higher absolute growth rate, and the fruit had the highest growth rate during the final swell of the core, corresponding to a consistent reduction in cladode growth rate. Cladode surface area extension in the first flush ceased at the time of summer fruit harvest (20 Aug.), while cladodes continued to increase in dry weight and thickness until the end of the growing season (November), and, eventually, during winter. The growth of fruit and cladodes of the summer flush occurred simultaneously over the course of the season; the cladodes had a similar surface area and a lower (25%) dry-weight accumulation and thickness than did first flush cladodes. The proportion of annual aboveground dry matter allocated to the fruits was 35% for the spring flush and 46% for the summer flush, being similar to harvest increment values reported for other fruit crops, such as peach [Prunus persica (L.) Batsch.]. Summer cladode pruning and fruit thinning should be accomplished early in the season to avoid resource-limited growth conditions that could reduce fruit and cladode growth potential.

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Joan R. Davenport and Carolyn DeMoranville

Native nitrogen is released when soils are mineralized. The amount of N released by this process depends on the amount of organic matter present and soil temperature. Cranberry (Vaccinium macrocarpon Ait.) grows in acidic soils with a wide range in organic matter content. To evaluate release of cranberry soil N at varied soil temperatures, intact soils were collected from sites that had received no fertilizer. Soils were cored and placed in polyvinyl chloride (PVC) columns 20 cm deep × 5 cm in diameter. Four different soil types, representing the array of conditions in cranberry soil (mineral, sanded organic, organic peat, and muck) were used. Additional columns of sand soil (pH 4.5) that had been pH adjusted to high (6.5) and low (3.0) were also prepared. Each column was incubated sequentially at six different temperatures from 10 to 24 °C (2.8 °C temperature intervals) for 3 weeks at each temperature, with the soils leached twice weekly to determine the amount of N release. The total amount of N in leachate was highest in the organic soils, intermediate in the sanded organic, and lowest in the sands. At the lowest temperature (10 °C), higher amounts of N were released in sanded organic and sand than in organic soils. This was attributed to a flush of mineralization with change in the aerobic status and initial soil warming. The degree of decomposition in the organic soils was important in determining which form of N predominated in the leachate. In the more highly decomposed soil (muck), most of the N was converted to nitrate. In the pH adjusted sand, high soil pH (6.5) resulted in an increase in nitrate in the leachate but no change in ammonium when compared to non-adjusted (pH 4.5) and acidified (pH 3.0) treatments. This study suggests that for cranberry soils with organic matter content of at least 1.5% little to no soil-applied fertilizer N is needed early in the season, until soil temperatures reach 13 °C. This temperature is consistent with the beginning of active nutrient uptake by roots. Soil N release from native organic matter was fairly consistent until soil temperatures exceeded 21 °C, indicating that when temperatures exceed 21 °C, planned fertilizer applications should be reduced, particularly in highly organic soils.

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Matthew L. Richardson, Catherine J. Westbrook, David G. Hall, Ed Stover, Yong Ping Duan, and Richard F. Lee

United States (i.e., California, Florida, and Texas) in the 1990s and early 2000s and has rapidly spread throughout these states and elsewhere ( Heppner, 1993 ; Legaspi et al., 1999 ). Adult citrus leafminers oviposit primarily on young elongating flush

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C.B. Watkins and F.W. Liu

/June but sometimes earlier depending on the season. Core browning (synonym core flush) is also a firm, moist disorder of ‘Empire’ and other apple cultivars and distinct from senile brown core ( Smock, 1977 ). Core browning incidence is affected by storage

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Yang Fang, Jeffrey Williamson, Rebecca Darnell, Yuncong Li, and Guodong Liu

, and individual growth flushes were not evident. Thus, treatment dates were not based on plant phenology. The 15 N treatment dates were 3 Mar. (25 d after budbreak), 2 Apr., 11 May, 18 July, 21 Aug., and 30 Sept. (after vegetative growth stopped). In

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Catherine J. Westbrook, David G. Hall, Ed Stover, Yong Ping Duan, and Richard F. Lee

The Asian citrus psyllid, Diaphorina citri , is a key pest in most citrus-growing regions around the world. D. citri nymphs feed exclusively on young elongating flush and feeding can retard leaf and shoot development ( Michaud, 2004 ; Shivankar

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Jennifer R. DeEll, Jennifer T. Ayres, and Dennis P. Murr

scald, soft scald, core flush, and greasiness is reduced by MCP J. Agr. Food Chem. 47 3063 3068 Fawbush, F. Nock, J.F. Watkins, C.B. 2008 External carbon dioxide injury and 1-methylcyclopropene (1-MCP) in the ‘Empire’ apple Postharvest Biol. Technol. 48

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Jennifer DeEll and Behrouz Ehsani-Moghaddam

.M. Mattheis, J.P. 1999a 1-Methylcyclopropene inhibits apple ripening J. Amer. Soc. Hort. Sci. 124 690 695 Fan, X. Mattheis, J.P. Blankenship, S.M. 1999b Development of apple superficial scald, soft scald, core flush, and greasiness is reduced by MCP J. Agr

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Joseph G. Robins, B. Shaun Bushman, Blair L. Waldron, and Paul G. Johnson

. Accessions were chosen to provide a broad representation of available Poa germplasm, particularly germplasm from arid regions of the world. Twenty-two of the accessions represented the KBG core collection that was developed to represent the diversity of

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Jennifer R. DeEll, Jennifer T. Ayres, and Dennis P. Murr

scald, core flush, and greasiness is reduced by MCP J. Agr. Food Chem. 47 3063 3068 Johnson, D.S. Colgan, R.J. 2003 Low ethylene controlled atmosphere induces adverse effects on the quality of ‘Cox's Orange Pippin’ apples treated with