Response Of Root And Tiller Development And Grain Yield And Quality To N-and Zn-Regulation In Wheat (Triticum Aestivum L.)

This study was carried out to clarify the occurrence and function of nodal roots in different tiller groups(especially nodal roots of ineffective tillers)of wheat,and the effect of nitrogen and zinc fertilizer on the development of roots and tillers.The experiments were conducted in Henan Agricultural High-tech Park(Zhongmu,Henan Province)and Yuanyang Science and Education Park of Henan Agricultural University from 2018 to 2020.The split-split-plot designs were used in the field experiments,and the main plots were varieties with 2 levels,namely,Zhoumai 27(C1)and Xi’nong 979(C2);the split plots were nitrogen application with 3 levels,namely,N0(0 kg·hm-2),N1(120 kg·hm-2),N2(240 kg·hm-2);the split-split plots were zinc fertilization with 2 levels,namely,Z0(0 kg·hm-2)and Z1(22.5 kg·hm-2).In addition,pot experiment was conducted in 2019-2020,and the fertilizer application and planting density were converted according to the field experiment.The main research results are as follows:(1)The nodal roots of different tiller groups and the nodal roots of ineffective tillers of wheat increased with the increasing of nitrogen fertilization,and they reached the maximum value at grain filling stage,then decreased slightly.The maximum number of nodal roots of culms,primary tillers,other tillers and ineffective tillers were 19.9,54.3,37.5 and 13.5 per plant(field experiment),19.4,42.0,23.9 and 11.8 per plant(pot experiment)during the whole growth period.Zinc fertilization increased the number of nodal roots in different tillers.The effects of combined application of nitrogen and zinc fertilizer on the nodal root number of different tillers reached a significant level(α=0.05).The root vigor of different tiller groups and ineffective tillers showed a trend of first decreasing,then increasing and then gradually decreasing,and it increased with the increasing of nitrogen and zinc fertilizer application,and the difference reached a significant level.The root vigor of ineffective tillers was significantly lower than effective tillers.(2)Combined application of nitrogen and zinc fertilizer could increase SPAD value of flag leaves and dry matter accumulation in shoot.SPAD value and dry matter accumulation in flag leaves of wheat effected by zinc fertilization significantly(α=0.05).The dry matter accumulation among different tiller groups varied greatly.Under the condition of this experiment,the contribution of primary tiller was the largest among the different tillers.(3)Combined application of nitrogen and zinc fertilizer could improve grain yield and quality of wheat.The effect of combined fertilization of nitrogen and zinc on grain yield and its components was mainly reflected in grains per spike,and the difference was significant,which indicated that the key to increase yield was to increasing the number of grains per spike under the condition of stable number of the spike per plant,especially the advantage of grain weight per spike of the culm.Under different cultivars and different nitrogen application rates,there were great differences in the ability of tillers and spikes formation at different tiller sites.The effect of zinc fertilizer on grain quality was mainly reflected in the zinc concentration of wheat grains,and the difference was significant(α=0.05),which showed that the culm grains< the primary tiller grains < the secondary tiller grains;The protein content,soluble sugar content and total starch content of different tiller groups were consistent as follows: the culm grains > the primary tiller grains > the secondary tiller grains.(4)The effect of combined fertilization of nitrogen and zinc on utilization of nitrogen of wheat was significant(α=0.05).It could increase the nitrogen accumulation in different tiller groups.In addition,nitrogen accumulation in different spike was as follows: ears of primary tillers > ears of secondary tillers > ears of culm.PFPN,NUPE,NUE,NHI were reduced by increasing nitrogen fertilization,but they were increased by increasing zinc fertilization.Therefore,PFPN,NUPE,NUE,NHI could be promoted by combined fertilization of nitrogen and zinc.(5)Correlation analysis showed that the nodal root number of ineffective tillers was significantly or extremely significantly positively correlated with the spike number per unit area,grain soluble sugar content and NUPE.And it was negatively correlated with NUE and starch content.There was a significant positive correlation between the number of nodal roots of ineffective tillers and the zinc content in grains,and negatively correlated with the number of grains per panicle and grain yield.The results showed that combined application of nitrogen and zinc could promote the development of the roots of effective tillers and ineffective tillers,and improve the root vigor and the utilization of nitrogen of wheat.The nodal roots of ineffective tillers began to occur at the returning stage,and reached the maximum value at the grain-filling stage,with a range of8~16 per plant.It also promoted the growth and development of wheat,especially high tillers absorbed nutrients from the soil,especially the absorption of zinc.Reducing the number of nodal roots of ineffective tillers and increasing the root vigor could promote the formation of grain yield and its quality.