Stomatal Responses in Rainfed Lowland Rice to Partial Soil Drying; Comparison of Two Lines

Previously; we demonstrated that root Ups in drying soil communicate with shoots for stomatal closure. hi rainfed Wand rice, despite further water being available at depth. This study examines variation between two lines in root. signals. Rice lines CT9993 and IR62266 were grown in the held, and in die greenhouse with the split-root root-sever wax-layer system, to investigate their responses to mild and severe water deficit by monitoring stomatal conductance leaf water potential and leaf ABA concentration, In We greenhouse root systems were divided, withholding water from one portion, and in some cases, severing the droughted portion of roots to remove be signal. Wax layers differing in strength were placed at hardpan depth. Roots of CT9993 were better able to penetrate the wax layers. IR62266 exhibited stronger than CT9993 with W62266's stomatal conductance dropping sharply under water deficit, and recovering at slower rates but less completely, when roots subjected to drying soil were severed. The greater stomatal response in IR62266 was associated with a higher leaf, ABA concentration during Car, inner deficit which in turn was associated with its greater number or roots in drying soil In the Held, a second reduction hi g was observed under severe water deficit, with stronger signals in IR62266 associated with more conservative water toe as soil drying intensified. To better exploit subsoil water in mild or transient water deficit, selection for reduced root signals might he warranted.