抄録
Differences between locations in potato root system were studied with four varieties. Climatic conditions in two locations were almost same, though soil types were different: Soil of Sapporo and Shimamatsu were alluvial clay loam and volcanic ash sandy loam, respectively. Root dry weight of surface soil (depth to 30 cm), leaf area and tuber dry weight were measured biweekly during the growing season. Growth rate, duration of increase, maximum value and duration of root DW and LAI were calculated from quadratic regression curves fitted to raw data. Maximum values in root DW and LAI were greater in Sapporo than in Shimamatsu. Two values showed highly significant correlation (r=0.951). Diffcrences were also found in morphological characteristics of root and shoot. Root diameter, stem diameter and stem length were significantly greater in Sapporo. Number of root per stem, however, were greater in Shimamatsu. Differences in maximum root dry weight between locations were based on root growth rate in early varieties, and on root growth rate and duration of root increase in late varieties. On the other hand, differences in maximum LAI were attributable not to growth rate but to duration of leaf increase which was longer than duration of root increase. Greater maximum root dry weight in Sapporo delayed leaf senescence, and root dry weight duration during tuber bulking period was coerrelated with leaf area duration. Greater root dry weight duration and leaf area duration in Sapporo did not increase tuber bulking rate, but prolonged duration of tuber bulking and increased tuber yield. If root system increases rapidly or longer, then leaf growth also continues longer, thus leaf senescence might be delayed. It should result in long maintenance of tuber bulking and increase of tuber yield.
