Effects Of Gibberellin And Paclobutrazol On The Yield And Lodging Of Direct-seeded Rice

To explore the effects of gibberellin and paclobutrazol on yield and lodging resistance of direct-seeded rice, this study used the guangliangyou558 as experimental materials, which were planted in Huazhong Agricultural University experimental fields in 2015. Gibberellin and paclobutrazol were used to treat the direct-seeded rice, respectively. The experiment was divided into two parts, one of which was the gibberellin test, and the other was the paclobutrazol and gibberellin collaboration test. The experimental materials were untreated as control(CK), treated with 10 mg / kg gibberellin during the tillering stage(G1), treated with 15 mg / kg gibberellin during the tillering stage(G2) and treated with 10 mg / kg gibberellin during the jointing stage(G3) in the gibberellin test.While the experimental materials were untreated as control(CK), treated with 300mg/kg paclobutrazol during the jointing stage(P1), treated with 10 mg / kg gibberellin during the tillering stage plus 300mg/kg paclobutrazol treatment during the jointing stage(P2) and treated with15 mg / kg gibberellin during the tillering stage plus 300mg/kg paclobutrazol treatment during the jointing stage(P3) in the paclobutrazol and gibberellin collaboration test.The main findings were as follows:1.In the gibberellin test, sprayed gibberellin during the tillering stage lead to higher yield, while sprayed gibberellin during the jointing stage resulted the lowest yield. Although sprayed gibberellin during the jointing stage significantly increased the grains per ear compared to the control, the seed set and the 103- grain weight were significantly lower than the control, as the result, the yield was significantly lower than the control. The reason why sprayed gibberellin during the tillering stage lead to significantly higher yield compared to the control was that the seed set and the 103-grain weight were significantly higher than the control under this condition.2.In the gibberellin test, sprayed gibberellin during the tillering stage lead to significantly higher stem and sheath output rate as well as conversion rate of the direct-seeded rice compared to the control. While sprayed gibberellin during the jointing stage lead to significantly lower net assimilation rate, crop growth rate, mature dry matter accumulation and stem and sheath conversion rate compared to the control.3. In the gibberellin test, sprayed gibberellin during the jointing stage lead to highest lodging index while the other three treatments had no significant difference with the control. Sprayed gibberellin during the jointing stage lead to significantly lower basal stem breaking-resistant strength and significantly higher lodging index compared to the control, as the result, the lodging resistance became worse than the control. However, there was no significant difference in the basal stem breaking-resistant strength compared to the control when sprayed gibberellin during the tillering stage..4. In the paclobutrazol and gibberellin collaboration test, there was no significant difference between the yield. Although sprayed gibberellin during the jointing stage significantly increased the grains per ear compared to the control, the seed set and the 103- grain weight were significantly lower than the control, as the result, there was no significant difference between the yield.5. In the paclobutrazol and gibberellin collaboration test, sprayed paclobutrazol during the jointing stage after the rice heading lead to significantly higher net assimilation rate and significantly lower leaf area index compared to the control. Meanwhile, there was no significant difference between the mature dry matter accumulation. Although sprayed gibberellin during the tillering stage plus the paclobutrazol treatment during the jointing stage significantly reduced the crop growth rate after the rice heading compared to the control, the stem and sheath output rate as well as conversion rate were significantly higher than the control, as the result, there was no significant difference between the yield. Sprayed paclobutrazol on the blades during the jointing stage lead to higher SPAD value than the control.6. In the paclobutrazol and gibberellin collaboration test, the lodging index in sprayed gibberellin during the tillering stage plus the paclobutrazol treatment during the jointing stage were significantly lower than the control. The basal internodes bending moment and the basal internodes broken bending moment in sprayed paclobutrazol during the jointing stage were significantly lower than the control. While the lodging index was similar with the control. However, the significantly lower basal internodes bending moment and lodging index than the control in sprayed gibberellin during the tillering stage plus the paclobutrazol treatment during the jointing stage caused better lodging resistance. In summary, the basal stem breaking-resistant strength in sprayed gibberellin during the tillering stage plus the paclobutrazol treatment during the jointing stage were significantly higher than sprayed paclobutrazol during the jointing stage, while the basal stem diameter and the basal stem wall thickness in sprayed gibberellin during the tillering stage plus the paclobutrazol treatment during the jointing stage were significantly higher than sprayed paclobutrazol during the jointing stage. Simultaneously, the lodging index in sprayed gibberellin during the tillering stage plus the paclobutrazol treatment during the jointing stage were significantly lower than sprayed paclobutrazol during the jointing stage, which caused better lodging resistance.