Hino Motosugi

Supercooling characteristics of some deciduous fruit trees as related to water movement within the bud

SummaryTo characterize and identify the freezing resistance mechanism of some deciduous fruit trees, woody stem and dormant buds of apple (Malus domestica ‘Tsugaru’), grape (Vitis labruscana ‘Muscat Bailey A’), peach (Prunus persica ‘Shimizu Hakuto’), Japanese pear (Pyrus pyrifolia ‘Nijisseiki’), and persimmon (Diospyros kaki ‘Hiratanenashi’) were used in the following experiments. On thermal analysis (TA), the woody stem tissues or the buds with woody stem tissue of all fruit trees used showed two exotherms, the high temperature exotherm (HTE) and the low temperature exotherm (LTE). The flower buds without woody stem tissue of peach and pear also had two exotherms, the HTE and LTE, and the LTE temperatures coincided with the LT50S of flower buds although the detection frequency of LTE in pear was considerably lower (<10%). Furthermore, in peach and pear, the LTE of buds without woody stem tissue and the LT50 of flower buds on woody stem were cooling-rate dependent, and those temperatures fell with a decr...

Rootstock effects on fruit quality of 'Fuji' apples grown with ammonium or nitrate nitrogen in sand culture

Abstract Fruit quality of ‘Fuji’ apples (Malus domestica Borkh.) grafted on three rootstock cultivars (a weeping-type clone of ‘Marubakaidou’ (Malus prunifolia Borkh. var. ringo Asami), MM.106, and M.26) were investigated in sand culture. The trees were grown in a nutrient solution with nitrogen supplied as ammonium or nitrate. With MM.106 and M.26 rootstocks, fruit from the trees fed with nitrate nitrogen were larger, had better surface color, higher soluble solids, higher levels of sugars, and higher acidity than those fed with ammonium nitrogen. Fruit from trees grafted on MM.106 and M.26 treated with ammonium nitrogen had higher N but lower calcium content than those treated with nitrate nitrogen. With M. prunifolia rootstocks, however, the form of nitrogen supplied had no influence on the surface color, juice quality, and mineral content of the fruit.

Freezing injury to persimmons (Diospyros kaki Thunb.) and four other Diopyros species during deacclimation in the spring as related to bud development

Abstract The cold hardiness of the buds in five cultivars of persimmon trees ( Diospyros kaki ) and four other Diospyros species during deacclimation in spring was examined by computer-assisted thermal analysis (TA) and by the freezing test under a constant freezing temperature (−10°C). TA revealed that the cold hardiness of the bud decreased, that is, exotherm temperature of the bud rose rapidly after budburst in all cultivars and species examined. The cold hardiness determined by the freezing test under a constant temperature was closely correlated with the developmental stage of the bud. It decreased rapidly as the bud swelled, and was the lowest around the time of budburst in all cultivars and species examined. After budburst, it gradually increased with shoot growth, somewhat differently with cultivars and species. In other words, all cultivars and species were the most susceptible to freezing injury at the budburst stage, but the cultivar- or species-specificity in cold hardiness was expressed by the hardiness of young shoots developed after budburst. Frost injury to persimmon trees caused by the untimely frost in mid-April at the experimental orchard of Kyoto University was discussed in terms of the time of budburst in each cultivar.