Response Of Wheat Leaf Vein Traits To Ploidy,Nitrogen And Water Supplies And Their Relationship With Leaf Physiological Functions

Leaf vein traits are one of the important functional traits of plants,and directly affect leaf water and photosynthetic assimilates transport,thus may determine the growth and development of the whole plant.As a major food crop widely planted,wheat has undergone a long evolutionary process,it is not clear how the traits of leaf veins have changed,and how these changes affect leaf physiological functions during this process.In addition,the prominent limiting factors in wheat production are water and nutrients.How different nutrients and water supplies affect the leaf vein system,thereby affecting leaf hydraulic physiological functions has been rarely reported.Therefore,field plots and pot experiments were used to study the response of wheat vein traits to increased ploidy,different nitrogen and water supplies and their relationship with leaf morphology,physiological functions and yield,thus providing a theoretical guidance for elucidating wheat leaf vein functions and high-yield breeding and cultivation of wheat.The major results of this paper were as follows:?1?There was an allometric relationship between the leaf vein traits and leaf structural traits in 30 different wheat materials.For large longitudinal veins?LLVs?and small longitudinal veins?SLVs?,vein density was significantly and negatively correlated with interveinal distance and vein diameter,and interveinal distance was significantly and positively correlated with vein diameter.Interveinal distance of LLVs,SLVs and transverse veins was positively correlated with each other.Vein density of LLVs and SLVs decreased,while their diameter and interveinal distance increased with the increase of leaf area and leaf mass per area.A trade-off relationship existed between total vein density and leaf area and leaf mass per area,and vein diameter and interveinal distance were coordinated with leaf area and leaf mass per area.?2?The evolution of leaf vein traits in wheat was different from that in angiosperms.With the increase of ploidy level,the vein density decreased,midrib+large longitudinal vein density,small longitudinal vein density,transverse vein density,total vein density decreased by 45.5%,26.6%,4.6%,28.1%respectively,while the interveinal distance?the interveinal distance of large longitudinal veins,small longitudinal vein,transverse veins increased by 76.9%,48.6%,22.3%respectively?,vein diameter?the diameter of large longitudinal veins,small longitudinal veins,transverse veins increased by 27.9%,35.8%,11.7%respectively?and areolar area?increased by 66.3%?increased,and the changes mainly occurred during the evolution stage from diploids to tetraploids.Midrib+large longitudinal vein density,small longitudinal vein density and total vein density were significantly and positively correlated with net photosynthetic rate,and significantly and negatively correlated with yield;interveinal distance,vein diameter,and areolar area were significantly and negatively correlated with net photosynthetic rate,but significantly and positively correlated with yield.?3?The responses of vein density to nitrogen and water supplies were different in irrigated-land and dryland cultivars,and vein density of dryland cultivar was more tighly related with leaf hydraulic physiological function.For irrigated-land cultivar Zhengmai 101,major vein density(VLA_major)decreased,minor vein density(VLA_minor)and total vein density?VLA?unchanged,and the proportion of minor vein density(Pro_minor)increased with the increased nitrogen and water supplies,whereas for dryland cultivar Changhan 58,VLA_minor,VLA_minorand VLA all decreased but the Pro_minordid not change with the increased nitrogen and water supplies.For Zhengmai 101,VLA_majorwas significantly and negatively correlated with the leaf hydraulic conductance and stomatal conductance,and Pro_minorwas significantly and positively correlated with leaf hydraulic conductance,stomatal conductance and transpiration rate.For Changhan 58,VLA_major,VLA_minorand VLA all were negatively and linearly or exponentially related with leaf hydraulic conductance,net photosynthetic rate and stomatal conductance.Moreover,negative and linear relationships existed between VLA_majorand instantaneous water use efficiency,between VLA_minor,VLA and transpiration rate,and a negative and exponential relationship existed between the Pro_minorand instantaneous water use efficiency,net photosynthetic rate,transpiration rate.