Effect of Regulated Deficit Irrigation on Growth of Root and Shoot in Winter Wheat

The effects of regulated deficit irrigation(RDI) on growth of roots and shoots of plants were experimentally investigated during the 2008—2009 and 2009—2010 growing seasons in pot-grwon winter wheat under rain-proof shelter condition in Huanghuaihai Region in China,aiming at offering theories basis for the establishment of RDI model for water-saving,high-yield,high quality and efficiency in crops.A two-factor randomize-block design was applied.The first factor designed different stages of water deficit,including five leaves-overwintering(Ⅰ),overwintering-turning green(Ⅱ),turning green-jointing(Ⅲ),jointing-heading(Ⅳ),and heading-maturing(Ⅴ).The other factor was different degree of water deficit with three levels by soil relative water content,which included light deficit(L),moderate deficit(M) and severe deficit(S) at stages of water deficit I to V,corresponding soil relative water content were 60%FC~65%FC(Field Capacity),50%FC~55%FC and 40%FC~45%FC,respectively.Totally,15 water deficit treatments with six replicates were designed and applied.Additionally,full irrigation treatment(75%FC~85%FC) during whole growing season with eighteen replicates was designed as control(CK).Such root system parameters as root dry weight,root weight density and root length density,and total shoot dry matter weight were measured synchronously in all water treatments during water stress period and after re-watering,respectively.The results indicated that there were different effects of RDI on growth of roots and shoots of winter wheat due to both phenological stages and degree of water deficit.Although the growth of root system in winter wheat was restrained severely in water stress period before jointing,there was a 'super-compensation effect' in root growth after re-watering.Moderate water stress(degree of water deficit was 55%FC~65%FC) had positive effects on the growth of roots before wintering.There were super-compensation effects on root growth after re-watering in different water deficit treatments from green-returning to jointing in wheat.RDI in winter wheat was able to increase the ratio of root to shoot(R/S),and the effect was more outstanding with the aggravation of the water deficit.The results suggested that RDI should be adopted as an effective approach to regulate the growth of root and shoot in winter wheat.