Study on the development of an easy evaluation method of root system activity changes with time and the optimum dry matter partitioning to root

试验比较了水稻品种Koshihikari在排水良好的稻田直播和移栽的效果。利用菲律宾的热带水稻品种，对旱地旱种和低地移栽的数据进行了分析。在所有实验中，根样本都是在连续两个山丘之间采集的。根生长动态分析--直播抽穗后和移栽成穗时根系干重最大。无论是直播还是移栽，新根的干重增长速率都在穗部分化期达到最大值。在生育前期，直播的死根率低于移栽，而新生根率与直播和移栽基本相同。因此，移栽水稻的根系寿命可能较短，从而加速了根系的周转，而Di…的根系则相反。直播稻的寿命越长，全根重最大值出现的时间越晚。热带水稻根系生长动态分析低地稻穗分化期和旱地稻穗分化期新根生长速率最大。旱地品种的最大新根生长速率高于低地品种。死根量为90~160gm-2，死根率为53~78%。根呼吸速率的简易估算为建立根干鲜重比估算根系呼吸速率的简易方法进行了进一步的数据积累。根干鲜重比是评价直播和移栽的根呼吸速率的较好指标。同样，在旱地和低地条件下，热带水稻的根呼吸速率与干/鲜重比都有很好的相关性。因此，根干鲜重比可作为评价根系呼吸速率的一个较好的指标。较少

Experiment was conducted to compare direct seeding in well-drained paddy field and transplanting using paddy rice cultivar Koshihikari. Analysis was also performed on the data obtained from dry seeding in upland and transplanting in lowland field using tropical rice cultivars in the Philippines. Root samples were collected just in between 2 hills in a row in all experiments.1. Analysis of root growth dynamics in KoshihikariWhole-root dry weight recorded a maximum after heading in direct-seeding and at panicle initiation in transplanting. Dry-weight growth rate of new root recorded a maximum at panicle initiation both in direct-seeding and transplanting. The percentage of dead root in direct-seeding was lower than in transplanting during the early growth stage, while the percentage of new root was about the same in direct-seeding and transplanting. Therefore, it seemed that roots of transplanted rice have shorter life which resulted in accelerated turn over of roots and that roots of di … More rect-seeded rice have longer life which resulted in later appearance of a maximum whole-root weight.2. Analysis of root growth dynamics in tropical riceMaximun new-root growth rate was observed at panicle initiation in lowland field and before panicle initiation in upland field. Maximum new-root growth rate in upland cultivars in upland field was higher than lowland ones in lowland field. The amount and rate of dead root were 90-160gm-2 and 53-78 %, respectively.3. Easy evaluation of root respiration rateFurther data accumulation for the development of an easy evaluation of root respiration rate by root dry/fresh weight ratio was conducted. Root dry/fresh weight ratio was demonstrated to be a good index for the evaluation of root respiration rate both for direct-seeded and transplanted Koshihikari. Similarly, root respiration rate correlated well with dry/fresh weight ratio in tropical rices both under upland and lowland conditions. Thus, root dry/fresh weight ratio was suggested to be a good index for the easy evaluation of root respiration rate. Less