Study On Tolerance Of Linum Usttatissimum And Fraxinus Mandshurica To Low Potassium Or Phosphorus And Regulation Of Gene Expression

Potassium(K)and phosphorus(P)are essential elements for the growth and development of plants.K deficiency in soils is widespread in China and forest land is mainly P deficiency.K and P fertilizer were extensively used,increasing production costs,accelerating the depletion of K and P resources,causing environmental pollution.Selecting and breeding of plant varieties with low K/P requirements will fundamentally solve this problem.In this study,flax and manchurian ash,typical herbaceous and woody plants in Heilongjiang Province were used as materials.The purpose of this study was to explore effects of low K/P on plant growth and regulatory mechanism of gene expression.The main progress was as follows:1.50 flax cultivars(lines)were used as materials to evaluate the K use efficiency in the field.The results showed:50 flax materials were divided into 3 categories by K use efficiency of fiber yield:low,middle and high K use efficiency.4 high K use efficiency varieties and lines Sofie,Yuan2012-306,Yuan2012-295,D93005-15-3 and 8 low K use efficiency varieties and lines Heiya No.20,m97020,Yuan2012-302,98019-10-29,03134-3,90018-3-1-28,D95010-10,92199-13-10 were selected.High K use efficiency Sofie's technical length,total fiber rate,fiber yield and seed yield were more than 10%higher than low K use efficiency Heiya No.20,reflecting the excellent characteristics of high K use efficiency.Plant height,technical length,fiber yield and total fiber rate in flax were significantly positively correlated with K use efficiency.4 characters can be used as main objective characters of high K use efficiency flax varieties.2.Effects of low K stress on the growth,development and yield traits of flax were studied by sand culture tests of 3 high K use varieties(lines)and 2 low K use varieties(lines)treated with 4 different K concentrations 1mmol/L(K1),3mmol/L(K3),6mmol/L(K6)and 12mmol/L(K12).The results showed:K6 was optimized for sand culture and technical maturing stage was the most sensitive stage to K deficiency.Biomass dry weight,root dry weight,root-shoot ratio,root volume,total root surface area,stem yield,fiber yield and total rate of flax under normal K supply K6 were significantly higher conditions than those under K1 and K3(K6>K3>K1).The highest demand for K during technical maturing stage,in order to obtain higher fiber yield and it is necessary to ensure adequate supply of K fertilizer.Decrease of biomass dry weight,root dry weight,root-shoot ratio,root volume,total root surface area and fiber yield of high K use efficiency Sofie and Yuan2012-306 was significantly lower than those of low K use efficiency Heiya No.20 and Yuan2012-302 under low K stress(K1).The results showed that varieties with high K use efficiency were more tolerant to low K stress,especially for fiber yield.It was suggested that K use efficiency of varieties should be properly planted in production.3.Differential expression analysis of K starvation response genes in high K use efficiency Sofie seedlings.The results showed:3 K transporter genes LusKC1(Lus K channel 1),LusSKOR(Lus STELAR K+outward rectifier)and LusHAK5(Lus high affinity K+transporter 5)were screened out.The response peak occurred at 12h and 96h.1154 differentially expressed genes(DEGs)(508 up-regulated and 646 down-regulated)were identified at K starvation 12h.247 DEGs(131 up-regulated and 116 down-regulated)were identified at K starvation 96h.18 genes were response to both two periods(8 up-regulated and 10 down-regulated).This research also screened 7 genes directly related to K in the DEGs,including 4 K transport proteins,2 K channel proteins and 1 sodium-potassium-calcium exchange protein.6 genes related to cellulose synthesis were screened,including 2 EXOCYST,3 COB genes and 1 FEI.These genes played an important role in the response of flax to K deficiency stress.4.Adaptability of high K use efficiency Sofie and manchurian ash to P stress and analysis of expression of WRKYs gene.The results showed:Biomass dry weight,and stem and leaf dry weight of flax and manchurian ash seedlings were significantly decreased under P deficiency.Root dry weight,root-shoot ratio,number of lateral roots,total root length and total root surface area of flax and manchurian ash seedlings were significantly increased under P deficiency which indicated that P deficiency significantly inhibited plant growth and development.Biomass distribution in the overground part of plant was reduced,and biomass distribution in the underground part of plant was increased to promote P absorption.Contents of IAA,BR,ETH and ACP activity in lateral roots of flax and manchurian ash seedlings were increased under P deficiency.Contents of GA3,CTK and ABA in lateral roots of flax seedlings were decreased under P deficiency which suggested that P deficiency promoted growth of lateral roots by regulating hormones contents and ACP activity in lateral roots.Expression of Lus WRKY7,LusWRKY22,LusWRKY48 and LusWRKY71 in lateral roots of flax seedlings significantly increased under P deficiency.Expression of FmWRKY6,FmWRKY23,FmWRKY44 and FmWRKY71 in lateral roots of manchurian ash seedlings significantly increased under P deficiency.These genes were involved in the regulation of P deficiency in flax and manchurian ash.5.Comparative analysis of P deficiency response of herbaceous flax and woody manchurian ash.The results showed:The effect of P deficiency on the phenotype and physiology of manchurian ash was similar to flax.But the difference in response was:Firstly,effect of P deficiency stress on biomass dry weight,stem dry weight and dry root weight related to plant growth of flax was relatively large.But effect of P deficiency stress on root-shoot ratio and lateral roots number related to lateral root development was relatively large in manchurian ash.Sencodly,response of hormones BR,IAA,GA3,CTK and ACP in flax to P deficiency stress was more obvious than that in manchurian ash.Thirdly,WRKYs in response were different.Response time of LusWRKYs transcription factor expression in flax was significantly faster than that in manchurian ash.Lateral root development of manchurian ash was significantly increased under P deficiency stress.Although the response of hormones,ACP and WRKYs was not as obvious as that of flax,enhancement of lateral root development promoted absorption of more P in the P deficient environment.So manchurian ash was more adaptable to P deficiency than flax.The results laid a foundation for comparative bilogy of P deficiency in herbaceous flax and woody manchurian ash.In conclusion,this study comprehensively explained flax dependence on K and flax and manchurian ash dependence on P from phenotypic,physiological and molecular mechanisms.It provided ideas for efficient cultivation of herbaceous flax and woody manchurian ash.Moreover,it provided reference for rational fertilization of soil K and P and genetic improvement of forest P related traits and P demand of forest land.