Partial Rootzone Drying Irrigation Increase Root Surface Area, Root Hydraulic Conductivity and Water Use Efficiency in Maize

Abstract

Partial root-zone drying (PRD) is an effective water-saving irrigation method and the heterogeneous soil moisture distribution induced by the method may affect root activities, crop water use efficiency and participation of different part of organ. The effects of deficit irrigation (DI) and PRD on leaf and root surface areas, root hydraulic conductivity (KR), and gas exchange and water use efficiency, were studied in maize (Zea mays L. cv., a local variety) grown in pots in the field for two months in the arid climate of Gansu Province, northwest of China in 2009. The PRD treatment was applied in two modes as PRD1 and PRD2, and they were obtained by the soil water content of the dry compartment had decreased to 18% (vol.) and 11% (vol.) (approximate 60% and 30% of the pot holding capacity) before shifting side of irrigation, respectively. DI2 was irrigated with the same irrigation amount with PRD2, while water was equally separated to two compartments. The full irrigation (FI), PRD1, PRD2 and DI2 received 10.75, 8.70, 8.45 and 8.45 liters of water during the treatment period, respectively. The evapo-transpiration water use efficiency (WUEET) was significantly higher in the PRD2 than in the DI2. PRD1 and PRD2 significantly (P<0.05) increased the root surface areas compared to DI2 by 17.8% and 14.6%, respectively, and that resulted in ratio of root surface area to leaf area of PRD2 significantly higher than that of DI2. Further, compared to DI2 and FI, PRD2 significantly (P<0.05) increased KR by 15% and 34%, respectively. The intrinsic WUE, the net photosynthesis (A) and gs relationship (A/gs), were the highest in the PRD2 treatment as compared with the other treatments on 4 f 5 occasions. On 3 out of 5 occasions, the A/gs values of PRD2 plants were significantly higher than those of FI plants. Our results indicate that PRD2 increased root-shoot surface ratio and the root hydraulic conductivity and those might play a major role in enhancing WUEET.