Effects of Wheat Straw-Residue Applied to Field and Nitrogen Management on Photosynthate Transportation of Stem and Sheath and Grain-Filling Characteristics in Super Hybrid Rice

Abstract

Grain filling is the final growth stage in cereals when fertilized ovaries develop into caryopses.The degree and rate of grain filling in rice spikelets differ largely with grain positions on a panicle and photosynthate accumulated in the stem sheath before and after flowering.A rice panicle is usually divided into inferior spikelets and superior spikelets,the poor grain-filling of inferior spikelets is more aggravated in the new bred "super" rice cultivars that have numerous spikelets on a panicle.In order to further investigate the mechanism,and the cultivation measures to improve the yield potential of "super" rice cultivars,two "super" hybrid indica rice cultivars,Yangliangyou 6 and Ⅱ you 084,were field-grown with treatments of two applications of wheat straw(all wheat straw residue applied to field,SRF;no wheat straw residue applied to field,NSRF) and two applications of nitrogen(the basic and tiller fertilizer to the panicle fertilizer=5:5,N1;and 7:3,N2).The accumulations of dry matter and NSC(non-structural carbohydrates) in stem and sheath,transportation percentage,and grain-filling characteristic in superior and inferior spikelets under nitrogen application amount of 225 kg ha-1 were measured.The results showed that the SPAD values of leaves and dry matter accumulation of stem and sheath in treatment of NSRF were higher than those in SRF before heading,which was on the contrary after heading.The SPAD values of the N2 were higher than those of the N1 before heading,but the dry matter accumulation of stem and sheath and its transportation percentage of the N2 were higher than those of the N1 at each growth stage,there was no significant difference before heading,while significant diffrence at heading and ripening periods.The interactions of the SFR and the N2 significantly enhanced dry matter accumulation in stem and sheath,output from stem and sheath,transportation percentage and NSC transportation percentage at mid and late grain-filling stages.Grain weight of the superior or inferior spikelets was positively and significantly or very significantly correlated with dry matter accumulation from heading to ripening,NSC accumulation in stem and sheath at heading,and dry matter weight in stem and sheath at ripening,while negatively and significantly correlated with NSC accumulation at ripening.The positive corrections between the initial growth power of the superior or inferior grains and the NSC accumulation of stems and sheath at heading,between the mean grain-filling rate and the NSC accumulation of stems and NSC transportation percentage at heading stage,between the maximum grain-filling rate of the superior grains and NSC accumulation and NSC translocation efficiency at heading,and between the maximum grain-filling rate of the inferior grains and the NSC transportation percentage were significant or very significant.