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Dongsheng Zhang, James R. Brandle, Kenneth G. Hubbard, Laurie Hodges and Entin Daningsih

The relationships between shelterbelt (tree windbreak)-induced microclimate and muskmelon (Cucumis melo L.) growth and development were investigated at the Univ. of Nebraska-Lincoln Agricultural Research and Development Center near Mead, Nebr., during the 1992 and 1993 growing seasons. Wind speed, wind direction, air and soil temperatures, relative humidity, and soil moisture were monitored in both sheltered and nonsheltered areas. Plant growth parameters (plant height, vine length, plant dry weight, and leaf area) were measured at various stages of development. Shelterbelts provided improved growing conditions for muskmelon transplants. Direct wind damage and duration of higher wind speeds were reduced 47% to 56% in sheltered areas. Air temperatures in sheltered areas were slightly higher during daytime and slightly lower at night, and significantly so early in the growing season. Relative humidity was increased significantly in sheltered areas in 1992 and, while higher in 1993, the difference was nonsignificant. Soil moisture content was not affected significantly by wind protection. Sheltered plants exhibited earlier development and faster growth. The first female flower appeared 2 days earlier in sheltered areas in both years. The first fruit set, as indicated by fruit swelling and retention on the vine, occurred 6 days earlier and matured 5 and 6 days earlier in sheltered areas in 1992 and 1993, respectively. Leaf areas and dry-matter accumulation of sheltered plants were greater than those of exposed plants. The shoot relative growth rate of sheltered plants increased earlier in the growing season, but decreased slightly later in the growing season. The earlier development and faster growth of sheltered plants were related mainly to the reduction of wind speed, higher total accumulated air temperatures during the daylight hours (sum of daily average daytime air temperatures based on hourly averages), and higher soil temperature in sheltered areas. Total yields were not affected significantly in either year; however, early yields were significantly greater in sheltered areas in 1993. If earlier maturity and increased yield are possible in large sheltered fields, this practice would provide an economic benefit to producers.

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Margarita R. Villagarcia, Wanda W. Collins and C. David Raper Jr.

Soil N availability is an important component in storage root production of sweetpotato [Ipomoea batata (L.) Lam.]. A controlled-environment experiment was conducted to characterize effects of N availability on patterns of dry matter, nonstructural carbohydrates, and N accumulation, and to determine possible components of N use efficiency that vary between two genotypes of sweetpotato. Rooted cuttings of `Jewel' and MD810 were transplanted into pots filled with sand and kept in a growth chamber for 72 days. Plants were watered during the first 30 days with a complete nutrient solution that contained 14 mm NO3 - and then for the next 42 days with one of three complete nutrient solution that contained either 2, 8, or 14 mm NO3 -. At 30, 44, 58, and 72 days after transplanting, three plants from each cultivar and treatment combination were sampled and separated into leaves, stems plus petioles, fibrous roots, and storage roots. Each plant fraction was freeze-dried, weighed, ground, and analyzed for total N, soluble sugars, and starch. Availability of N in the substrate, which limited dry matter accumulation at 2 mm NO3 -, was nonlimiting at 8 and 14 mm NO3 -. In both genotypes, net assimilation rate, efficiency of N use (i.e., increments of dry matter accumulated per increment of N taken up), and proportion of dry matter allocated to storage roots were greater for N-stressed (2 mm NO3 -) than N-replete (8 and 14 mm NO3 -) plants. For the N-stressed plants, however, efficiency of N use was greater in MD810 than in `Jewel'. Although rate of NO3 - uptake per unit fibrous root mass was similar in the two genotypes under the N stress treatment, MD810 had greater uptake rate than `Jewel' under nonlimiting availability of NO3- in the substrate. The increased rate of uptake under nonlimiting NO3 - supplies apparently was related to enhanced rates of carbohydrate transport from shoots to roots. As tissue concentration of N declined in response to the lowest application of NO3 -, shoot growth was limited prior to, and to a greater extent than, the photosynthetic rate. The resulting relative decline in sink activity of shoots thus presumably increased the availability of carbohydrates for transport to roots.

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Wook Oh, Erik S. Runkle and Ryan M. Warner

≤ 0.05. Shoot dry mass of seedlings at transplant showed trends somewhat similar to those of leaf number. When seedlings were provided with the same duration of high light, SL promoted dry matter accumulation more during the latter period than

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Samuel Salazar-García, Luis E. Cossio-Vargas, Isidro J.L. González-Durán and Carol J. Lovatt

-applied gibberellic acid (GA 3 ) on the date ‘Hass’ avocado fruit reached legal maturity (mesocarp dry matter 21.5% or greater). z Rate of fruit growth and dry matter accumulation. At the time of the first GA 3 application of year 3 (15 July 2005

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Thomas Graham and Michael A. Dixon

. Results Expt. 1. The results of Expt. 1 are summarized in Figure 2 . Both thallus area and dry matter accumulation were reduced by the treatments beginning at CT 1.25 mg·L −1 ·min when compared with the control. Fig. 2. Liverwort thallus area ( A ) and

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Yai Ulrich Adegbola and Héctor E. Pérez

studies could confirm the levels of dry matter accumulation in G. pulchella . Furthermore, tolerance to high levels of desiccation stress is reasonable given that G. pulchella occurs naturally within coastal dune ecosystems and other habitats

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Shinsuke Agehara and Daniel I. Leskovar

accumulation and partitioning. Shoot dry matter accumulation at 1 DBT was inhibited by all ABA treatments in the two cultivars ( Fig. 5A ). The reductions were 17% to 21% in ‘Summer Flavor 800’ (391 vs. 309 to 325 mg) and 16% to 23% in ‘Summer Sweet 5244’ (465

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Martin P.N. Gent

depletion of starch rather than the much larger effect expected if nutrient uptake changed more or less than dry matter accumulation. Thus, changes resulting from shade in dry matter accumulation must have been similar to the changes in nutrient uptake. The

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Ibukun T. Ayankojo, Kelly T. Morgan, Monica Ozores-Hampton and Kati W. Migliaccio

), tomato total dry matter accumulation was generally lower for spring season (ranged from 29 to 47 kg·ha −1 ) than for fall (ranged from 354 to 454 kg·ha −1 ) ( Table 3 ). However, as temperatures increased in the spring season, total dry biomass

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Ryo Matsuda, Chieri Kubota, M. Lucrecia Alvarez and Guy A. Cardineau

. Fruit TSP concentration per unit DW decreased as FGI increased in both control and high EC ( Fig. 2A ). On the other hand, TSP content per whole fruit linearly increased with increasing FGI ( Fig. 2B ), indicating that dry matter accumulation had a