SUPERCOOLING CHARACTERISTICS OF SOME DECIDUOUS FRUIT-TREES AS RELATEDTO WATER-MOVEMENT WITHIN THE BUD

Citation
Sk. Kang et al., SUPERCOOLING CHARACTERISTICS OF SOME DECIDUOUS FRUIT-TREES AS RELATEDTO WATER-MOVEMENT WITHIN THE BUD, Journal of horticultural science & biotechnology, 73(2), 1998, pp. 165-172
Citations number
27
Categorie Soggetti
Horticulture
ISSN journal
14620316
Volume
73
Issue
2
Year of publication
1998
Pages
165 - 172
Database
ISI
SICI code
1462-0316(1998)73:2<165:SCOSDF>2.0.ZU;2-8
Abstract
To characterize and identify the freezing resistance mechanism of some deciduous fruit trees, woody stem and dormant buds of apple (Malus do mestica 'Tsugaru'), grape (Vitis labruscana 'Muscat Bailey A'), peach (Prunus persica 'Shimizu Hakuto'), Japanese pear (Pyrus pyrifolia 'Nij isseiki'), and persimmon (Diospyros kaki 'Hiratanenashi') were used in the following experiments. On thermal analysis (TA), the woody stem t issues or the buds with woody stem tissue of all fruit trees used show ed two exotherms, the high temperature exotherm (HTE) and the low temp erature exotherm (LTE). The flower buds without woody stem tissue of p each and pear also had two exotherms, the HTE and LTE, and the LTE tem peratures coincided with the LT(50)s of flower buds although the detec tion frequency of LTE in pear was considerably lower (<10%). Furthermo re, in peach and pear, the LTE of buds without woody stem tissue and t he LT50 of flower buds on woody stem were cooling-rate dependent, and those temperatures fell with a decrease in cooling rate. Water migrati on from the flower primordia of both buds to the surrounding tissues w as also observed during freezing. In apple, although the LTE of bud wi thout woody stem tissue was not detected in our experiment, the LT50 o f the bud was cooling-rate dependent, and water migration from the pri mordia to the other tissues in bud was observed during freezing. These facts indicate that the mechanisms of freezing tolerance in apple flo wer buds are the same as in peach and pear flower buds. Contrarily, in persimmon and grape, flower buds without woody stem tissue showed onl y one exotherm whose temperature was closely associated with the LT50 of the bud. Also, both the exotherm temperature of bud without woody s tem tissue and the LT50 of buds on woody stem were independent of cool ing rate. Persimmon buds showed no changes in the water content of eit her the primordium or the surrounding tissue during freezing, indicati ng no water migration from the primordia to the surrounding tissues. I n addition, provascular strands were found between the bud axis and fl ower primordia in apple, peach, and pear buds, but not in persimmon an d grape buds. From these results, the buds of apple, peach and pear ma y acquire freezing resistance by extra-organ freezing, but grape and p ersimmon buds are likely to supercool by themselves.