The Root-sourced Signals, Osmotic Adjustment And Its Relation To Yield Formation Of Naked Oats Under Drought

The pot experiments were carried out to investigate the relationships of root-sourced signals, osmotic adjustment and grain yield of five naked oat (Avena sativa L.) cultivars. Two early-released cultivars, Laoyoumai (LY,1950s) and Yanmai (YM,1950s), and three recently-released cultivars were, Dingyou5(DY5), Dingyou6(DY6) and Dingyou7(DY7) were used in this studies. The performance of root-sourced signals, osmotic adjustment, grain yield and water use efficiency for grain (WUEg) of five naked oat cultivars under drought stress were recorded, and their relationships were analyzed. The main results as follows;1. The non-hydraulic root-sourced signal (nHRS) and hydraulic signal (HS) of naked oat cultivars were triggered in turn during the gradually soil drying. The soil water content (SWC) threshold range of nHRS for LY, YM, DY5, DY6and DY7were59.0-34.7%FWC (field water content)(24.3%FWC),56.4-31.6%FWC (24.8%FWC),51.8-35.0%FWC (16.8%FWC),60.4-34.1%FWC (26.3%FWC) and51.8-30.1%(21.7%FWC) respectively. Therefore, the SWC threshold range of nHRS was not be broadened in recently-released cultivars, comparing to that of early-released cultivars.2. The leaf water potential (WP), leaf osmotic potential (OP) and leaf turgor potential (TP) were measured in naked oat cultivars to evaluate their threshold range of osmotic adjustment. The threshold range of osmotic adjustment for LY, YM, DY5, DY6and DY7were-1.295～-1.492MPa,-1.273～-1.493MPa,-1.237～-1.727MPa,-1.274～-1.768MPa and-1.342～-1.781MPa, respectively; Which shows the osmotic adjustment ability in recently-released cultivars were better than that of early-released cultivars.3. The lethal leaf water potentials of five naked oat cultivars were compared as follows:YM (-3.15MPa)> LY (-3.77MPa)> DY5(-4.50MPa)> DY6(-5.55MPa)> DY7(-6.02MPa); the lethal leaf water potential was lower in recently-released cultivars, which showed higher desiccation tolerance. Correlation analysis showed lethal leaf water potential was negatively correlated to the SWC threshold range of osmotic adjustment (r2=-0.801, P>0.05).4. Yield formation experiment showed that grain yield, harvest index (HI) and water use efficiency for grain (WUEg) in recently-released cultivars were higher than that in early-released cultivars, no matter which water-supply regions (90%,55%,35%FWC). At moderate water stress (55%FWC), the grain yield negatively correlated to the SWC threshold range of nHRS (r2=-0.881, P<0.05), and positively correlated to the threshold range of osmotic adjustment (r2=0.886, P<0.05); whereas at the severe water stress (35%FWC), there were no significant correlation between grain yield neither the SWC threshold range of nHRS (P>0.05) nor the threshold range of osmotic adjustment (P>0.05). In addition, the WUEG were significantly correlated with the threshold range of osmotic adjustment at both water stress regions (55%,35%; r2=0.952, P<0.05; r2=0.981. P<0.01). In conclusion, the improvement for osmotic adjustment and desiccation tolerance in recently-released cultivars during breeding process, were contributed to their grain yield under drought condition.