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

对水田直接播种与光光水稻移栽进行了比较试验。还对菲律宾热带水稻品种旱作播种和低地移栽的数据进行了分析。在所有试验中，根样均采集于2个垄之间的一排。直播抽穗后全根干重最大，移栽穗形成时全根干重最大。直播和移栽时，新根干重生长速率在穗萌发时最大。在生长早期，直播的死根率低于移栽，而直播和移栽的新根率基本相同。因此，移栽水稻的根系寿命较短，导致根系翻转速度加快，而直种水稻的根系寿命较长，导致全根重最大值出现较晚。热带水稻根系生长动态分析：观察了低地田穗形成时和旱地穗形成前的最大新根生长率。旱地品种在旱地的最大新根生长率高于旱地品种。死根数量为90 ~ 160gm-2，死根率为53 ~ 78%。根呼吸速率简易评价为建立根干/鲜重比简便评价根呼吸速率提供了进一步的数据积累。根干鲜比是直接播种法和移栽法评价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/鲜重比具有良好的相关性。因此，根干鲜比是评价根呼吸速率的一个较好指标。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