The Root-shoot Coordination And Regulation Of Rain-fed Spring Maize On The Loess Plateau

Drought is a wordwide problem,and root acts like a bridge directly connecting soil resources and plant canopy.The root-shoot relationship means a balance between soil exploration and aboveground growth.Developed from traditional plastic film-mulching planting measures,the dry-land full film-mulching high-yield maize system?FM?integrates ridge-ditch rain collection and furrow planting technique,has been widely used in arid agricultural region of Loess Plateau.However,there is still little information about the root-shoot development of crop plants with FM.The productivity of rain-fed crops grown with FM technique is directly related to the availability coincides of water and heat in both time and space underground.As soil hydrothermal conditions were significantly improved under FM,the relationship of root-shoot should also be different.Therefore we hypothesized that the establishment of high-yield and high-efficiency maize?Zea mays L.?population under FM is built on robust plant development and indispensable soil support that generally contributed by an optimization of synergetic shoot-root growth relationship.Aimed to verify this hypothesis and reveal the core and profound root-shoot relationship under FM,we carried out several field studies in a typical arid farming region of Changwu,Shannxi province.In situ plant collection and indoor professional methods were used to investigate the high yield characteristics and root support of maize plants with FM,and the major results were listed as follow:?1?Root was not the right focus of seedlings at the V3 stage in FM treatment.And FM helped seedlings more constantly to concentrate on canopy growth both at the V3 and V6 stage.The shoot to root ratio of FM plants increased by 25%and 213%at V3 and V6stage,as compared with the CK treatment respectively.It makes sense that the improvement of soil water and heat conditions under FM treatment effectively helped maize seedlings to better distribute limited photosynthate to the aboveground part during the early growth phase.And this modification,in return substantially boosted the whole plant development in a long run.?2?FM can clearly accelerate the maize growth of the vegetative stage and prolong the reproductive growth period by about 1 week,thereby largely enhancing biomass production time after flowering.The accelerated vegetative stage was closely related to the improvement in soil hydrothermal conditions since the early vegetative stage.?3?FM can significantly advance the accumulation of N and biomass in leaves but dramatically reduce root biomass?RB?and root to shoot ratio after flowering.Moreover,the root growth of FM during the reproductive growth period was not simply light and shallow,but there was more efficient and long-lasting support from below ground..?4?Below suitable N rate?250 kg/ha?,the biomass allocation between reproductive organs?Ear?and non-productive organs?i.e.,leaf,stem and root?was negative correlation in maize plant after flowering.And above suitable N rate,excess N input?380 kg N/ha?cannot increased ear biomass?EB?but significantly increased RB and stem biomass?SB?.?5?It was the root length?RL?in deep soil,but not the total RL underground,which had a close connection with the soil N utilization of FM plant after flowering.And it seems that the increase of N rate promoted the RL accumulation in top 20 cm soil in reproductive stage.In addition,when compared with 0 N rate under FM treatment,the RL decrease rate of 250 kg N ha^-1decreased by 26%,and that of 380 kg N ha^-1decreased by 47%.?6?The synergetic root-shoot response of FM maize plant to higher plant density and higher N rate,were actually lower shoot-root ratio per plant and higher biomass production per hectare.Our results indicated that FM plant with higher density and N input rate had more RB accumulation and lower shoot-root ratio.In summary,our result showed that canopy development was the core of high-yield of FM maize plant.The shoot-root relationship of high-yield maize plant with FM indicated an optimal balance between soil exploration and aboveground yield formation.The root growth had great effects on the canopy development and yield formantion of maize plant.And as soil hydrothermal conditions were largely improved in FM maize field since sowing,the root development and root-shoot relationship of FM plant were significantly changed.Especially during the key time of yielding after flowering,maize root with FM had a light,shallow but more efficient and long-lasting support from below ground.It was the optimized shoot-root relationship under FM,which better balanced the soil exploration and aboveground development,substantially boosted the whole plant development and final yield.