Abstract: The study with 25 two-line hybrid rice strains showed that their water retaining capacity was different with their combinations.On the whole,the water content in leaf and stem-sheath decreased during heading-grain filling stage,while that in panicle increased first and then decreased,with a peak at 7th day after heading.Stem-sheath was the main organ for water retaining. The correlation of panicle yield with both leaf and stem-sheath water content was positive at the 1st day after heading but became negative later,and that with whole stem-plant water content was positive after heading.The chlorophyll content of the two-line hybrids increased first and then decreased,with a peak at the 7th day after heading.Comparing with normal rice (male parent),the chlorophyll content of most two-line hybrids was lower,and the decreasing rate was faster than that of normal rice after heading. For two-line hybrid rice breeding,it should preferentially consider to select those hybrids which have a clearer dominance of plant water retaining capacity and a higher chlorophyll content at earlier and middle heading-grain filling stage,and an obvious dry matter transportation from leaf and stem-sheath at later heading?grain filling stage.For two?line hybrid rice planting,it should not only pay attention to the supply of water and nutrients,especially nitrogen at earlier and middle heading-grain filling stage,but also control nitrogen and water in time to prevent leaf green clinging and to promote dry matter transportation from leaf and stem-sheath to grain at later heading-grain filling stage.

Key words: Nutrient recycling and reutilization, Long term field experiment, Soil nutrient budget