Dear Editor,Roots,as a major organ of plants,are involved in nutrient and water acquisition,and might play a vital role in yield increase and efficient N absorption with genetic improvement.Because of the great differences in growth period and pattern between the old and new rice cultivars,it is difficult to clarify how genetic improvements contribute to root growth in rice.For example,for a solution culture system,Wu et al.suggested that total root length increased with increasing year of release for maize hybrids,while shoot dry weight, Dear Editor, Roots, as a major organ of plants, are involved in nutrient and water acquisition, and might play a vital role in yield increase and efficient N absorption with genetic improvement.Because of the great differences in growth period and pattern between the old and new rice cultivars, it is difficult to clarify how genetic improvements contribute to root growth in rice. For example, for a solution culture system, Wu et al. culminating in total root length increased with increasing year of release for maize hybrids, while shoot dry weight,