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  • Author or Editor: T. D. Liu x
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Pectin is a class of complex polysaccharides that function as hydrating agents and cementing materials for the cellulose network. Pectin has various health benefits, such as decreasing serum cholesterol levels, alleviating diabetes mellitus, and preventing cancer. It has been reported that the cancer prevention effect is closely related to the structure of pectin (galactose-rich, molecular weight <10,000, and methylation degree 50% to 70%). This study was conducted to investigate the variation of grapefruit pectin content due to harvest time. `Rio Red' grapefruit on sour orange rootstock grown at Texas A&M Univ.-Kingsville Citrus Center were harvested every 2 months and analyzed for pectin content, galacturonic acid concentration, methylation degree, and neutral sugar composition. Results showed that lamella contains more pectin than flavedo and albedo. In the lamella, the edible section, the uronic acid content ranged from 85% to 90% from August to April the following year. Methylation degree increased from August (31.89%) to April (46.99%). Total neutral sugar content of lamella pectin decreased from 110.54 to 61.77% mg·g -1. Galactose, arabinose, and rhamnose are the major sugar contents of pectin (85%), and glucose content increased with the season from 3.14 to 13.34 mg·g-1. Molecular weight of pectin was also determined.

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Effective nutrient and irrigation management practices are critical for optimum growth and yield in open-field fresh-market tomato production. Although nutrient and irrigation management practices have been well-studied for tomato production in Florida, more studies of the current highly efficient production systems would be considered essential. Therefore, a two-season (Fall 2016 and Spring 2017) study was conducted in Immokalee, FL, to evaluate the effects of the nitrogen (N) rates under different irrigation regimes and to determine the optimum N requirement for open-field fresh-market tomato production. To evaluate productivity, the study investigated the effects of N rates and irrigation regimes on plant and root growth, yield, and production efficiency of fresh-market tomato. The study demonstrated that deficit irrigation (DI) targeting 66% daily evapotranspiration (ET) replacement significantly increased tomato root growth compared with full irrigation (FI) at 100% ET. Similarly, DI application increased tomato growth early in the season compared with FI. Therefore, irrigation applications may be adjusted downward from FI, especially early during a wet season, thereby potentially improving irrigation water use efficiency (iWUE) and reducing leaching potential of Florida sandy soils. However, total marketable yield significantly increased under FI compared with DI. This suggests that although DI may increase early plant growth, the application of DI throughout the season may result in yield reduction. Although N application rates had no significant effects on biomass production, tomato marketable yield with an application rate of 134 kg·ha−1 N was significantly lower compared with other N application rates (179, 224, and 269 kg·ha−1). It was also observed that there were no significant yield benefits with N application rates higher than 179 kg·ha−1. During the fall, iWUE was higher under DI (33.57 kg·m−3) than under FI (25.57 kg·m−3); however, iWUE was similar for both irrigation treatments during spring (FI = 14.04 kg·m−3; DI = 15.29 kg·m−3). The N recovery (REC-N) rate was highest with 134 kg·ha−1 N; however, REC-N was similar with 179, 224, and 269 kg·ha−1 N rates during both fall and spring. Therefore, these study results could suggest that DI could be beneficial to tomato production only when applied during early growth stages, but not throughout the growing season. Both yield and efficiency results indicated that the optimum N requirement for open-field fresh-market tomato production in Florida may not exceed 179 kg·ha−1 N.

Open Access

Abstract

The effect of 12 and 16 hours of light on flowering was studied in field plot experiments with 1602 accessions of mung bean (Vigna radiata var. radiata) and 4 related species. Mung bean, adzuki bean, (V angularis (Willd.) Ohwi & Ohashi var. angularis) and moth bean (V. aconitifolia (Jacq.) Marechal) appear to have a high incidence of day-neutral types when compared with the black gram (V. mungo (L.) Hepper) and rice bean (V. umbellata (Thumb.) Ohwi & Ohaski) germplasm collections of mung bean and related species show an increase of day-neutral types of latitudes distant from the equator.

Open Access