STUDIES ON THE ROOT DEVELOPMENT OF HYBRID RICE
Hybrid rice plants(Oryza sativa L).both hybrids “San-you 2”and“Se-you 2” were used as testing materials,and cultivars“Hong-410”、“Da-jia-huo”、 and “San-bang-70-luo”as control in this study.They were grown both in pots and field plots in 1978-1980.Treatments were carried out during the periods of 2、4、6、8、10、12、14、16、leaf-stage,milk stage,dough stage and maturation stage、at each stage the formation of superficial root,bleeding sap of stem, volume and dry weight of roots.and potency of rooting etc.were measured. The results obtained are briefly described as follows. 1.Both plants of hybrids“San-you 2”and “Se-you 2”,had the diameter, volume,and dry weight of roots(the density of superficial roots)larger than those of rice cultivars“Hong 410”,“Da-jia-huo”,but the diameter and dry weight of roots were less than those of cultivars“San-bang-70-luo”with respect to the formation of lateral roots.Visual observations showed that “San-you 2”,“Se-you 2”and“San-bong-70-luo”branched up to fifth order, while those of“Hong-410”,“Sai-zai-ho”branched up only to tertiary. 2.Both plants of hybrids“San-you 2”and“Se-you 2”.showed the maximum weight of roots,the maximum power of sap bleeding and the maximum potency of rooting during the dough stage,and 14 leaf-stage re- spectively.However,the maximum development of rooting per day was reached at about the time of the highest tillering activity.Since then the climax of sap bleeding per day was reached,and at the same time increase of tillers con- tinued up to the greatest tiller development.Then,some of the tillers died, making the total number of tillers declined.The dry weight of roots increased up to the boot stage.However,sap bleeding per day occurred in dough stage as the secondary summit. 3.When roots were cut at 4、6、8、leaf-stage,the number of tillers reduced with the number of panicles decreased.Kernels per paricle and filled grains decreased when the root was cut at 12 leaf-stage,furthermore,the rate of filled grains were much less than the control,when the roots were leaf-stage. 4.Roots of multiple tiller seedlings were much well developed than those of multiple seedlings per hill. Irrigated field plots with water layer at early growth stage and maintenance of wetness hereafter induced active growth of rice roots.