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Yoon Y.-W.,Sweet Persimmon Research Institute | Choi S.-T.,Sweet Persimmon Research Institute | Park D.-S.,Sweet Persimmon Research Institute | Rho C.-W.,Research and Development Bureau | And 2 more authors.
Korean Journal of Horticultural Science and Technology

To understand changes in composition and distribution of nutrients during early shoot growth of persimmon, organic compounds and inorganic elements of terminal shoots were analyzed for about 40 days from the time of foliation. Sample shoots were collected from mature ‘Fuyu’ trees for this three-year experiment and they were divided to stem, leaves, and the fruits including flower buds at the earliest stage. During shoot growth, concentration of soluble sugars increased in both leaves and fruits, but that of starch increased only in leaves. Those of amino acids tended to decrease in all the parts but there was no consistent change in proteins. As shoots grew, contents of all the organic compounds in a shoot increased, and they were especially higher in May leaves accounting for more than 60% of the shoot total for each nutrient. Along with shoot growth, concentrations of N and P gradually decreased in all three parts, while K decreased only in stem. However, those of Ca and Mg did not show notable changes in all the parts with wide variations depending on the year. Due to the quantitative increase in growth, contents of inorganic elements in a shoot increased in all the parts and the leaves accounted for 54-82% of the shoot total. At the cessation time of extension growth, a shoot contained 526-768 mg of soluble sugars, 245-844 mg of starch, 26-31 mg of amino acids, and 66-103 mg of proteins for three years. On the other hand, a shoot contained 203-388 mg of K, the greatest among the inorganic elements, followed by 132-159 mg of N. Changes of the nutrients in a shoot were much greater during the earlier stage of growth after foliation than during the later stage toward growth cessation, suggesting the importance of mobilizing reserve nutrients for the early growth of the shoots. The results of this study also suggested that the rate of nutrient changes, especially during the earlier stage of shoot growth, could be affected by environmental and cultural conditions. © 2014 Korean Society for Horticultural Science. Source

Choi S.T.,Sweet Persimmon Research Institute | Park D.S.,Sweet Persimmon Research Institute | Hong K.P.,Sweet Persimmon Research Institute | Shin H.Y.,Gyeongsangnam do Agricultural Research and Extension Services | And 2 more authors.
Acta Horticulturae

Maintaining low height has been a key practice for efficient management of persimmon orchards in Korea. Since no dwarfing rootstocks are commercially available to date, tree height is lowered most easily by heavy pruning, after which excessive shoot growth with low yield can hardly be avoidable. Therefore, the importance of stabilizing the vigor of lowered trees cannot be overemphasized. To lower tree height, large scaffolds are removed stepwise extending over several years. Leaving many one-year-old shoots at dormant pruning, thereby increasing leaf area as well as the number of fruits, significantly decreases the occurrence of water sprouts in vigorous trees with no appreciable yield reduction. Trunk girdling in early summer is one of the options to quickly reduce excessive shoot growth. When the shoots grow vigorously, the extent of fruit growth may be less than anticipated at the conventional level of flower bud thinning, which leaves a bud a shoot. Under such circumstances, it is recommended to leave 1.5 to 2 buds per shoot before flowering, followed by the final adjustment of fruit numbers after the physiological drop. When the lowered trees are vigorous, it is necessary to reduce N applications. Foliar application of prohexadione-Ca at 100-200 mg.L-1 (ppm) significantly reduces the growth of water sprouts and secondary shoots without adverse effect on the fruits. Combination of different measures may have to be considered depending on the degree of tree vigor. Source

Park D.S.,Sweet Persimmon Research Institute | Choia S.T.,Sweet Persimmon Research Institute | Hong K.P.,Sweet Persimmon Research Institute | Kim J.C.,Korean Society for Persimmon Science and Industry | And 2 more authors.
Acta Horticulturae

'Kojongsi', an astringent Korean native, has been one of the most popular cultivars used for the production of dried fruits. However, at a major growing area, the fruit often cracks during the late season. The cracking begins from the calyx, resulting in the decrease of the yield and the increase of fungal infection during drying. In this study, we monitored the relationship between seed development and the occurrence of this disorder. Two variables for seed development included (a) artificial- or non-pollination and (b) the presence or absence of pollinizers. The non-pollination treatment was done by screening visiting insects. Three percent of the fruits were seedless in pollinated trees, in sharp contrast to 100% in non-pollinated counterparts. Fruits from the trees with pollination cracked 0%, while those with non-pollination did 88%. The orchards with and without pollinizers produced 15.3 and 100% seedless fruits, respectively, 5.9 and 29.2% of which were cracked. Results strongly suggested that the inhibition of normal seed development was related to the occurrence of this disorder. Management to ensure good pollination may be an essential prerequisite to reduce the late-season cracking of this cultivar. Source

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