Physiological Ecology Response Of Different Broomcorn Millet Genotypes Under Low Phosphorus Stress

Phosphorus is a key element for plant growth, Crop mainly absorbphosphorus elements from soil by root. The utilization efficiency of Pfertilizers applied in fields is very low; the rock P resource is non-–reproductive and would be exhausted in future, Under thesesituations, it is urgent to breed low P tolerance crop genotypes bybio-techniques. As the more stable grain crops in the arid andsemi-arid area, Broomcorn millet have certain advantages of location.Using the soil culture experiment and nutrient solution, thecharacteristics of morphological, nutrient characteristics ofphosphorus and the physiological responses under the P-deficiencycondition were researched. It provide theoretical basis for the furtherstudying patience mechanism and genetic improvement under theP-deficiency condition of Broomcorn millet.(1)With six broomcorn millet genotypes (Yidianhong, Yushu NO.1,Jinshu NO.2, Jinshu NO.3, Chengshu95 and Chengshu104) wereplanted in the soil culture experiment and supplied with threephosphorus level. Study characteristics of the morphological andphysiological at different development stages. The results showedthat the plant height, leaf area, shoot dry weight of differentBroomcorn millet genotypes were all decreased under low P stress, but root dry weight, total root length and root surface area wereincreased, and have the highest variation coefficient in LP1 ofphosphorus level. Root shoot ratio increase obviously, at the averagegrowth extent from 61.6% to 76.57%, and that of Yushu NO.1 andChengshu104 increased mostly. The total P contents of differentbroomcorn millet genotypes were decreased under low P stress, butPhosphorus utilization efficiency were increased. The correlationanalysis showed that plant phosphorus efficiency significantlyrelated to the P uptake efficiency which is the main contributor to Ptolerance at low phosphorus stress.(2)The activation of superoxide dismutase(SOD), catalase(CAT),peroxidase(POD) of different Broomcorn millet genotypes wereincreased, compared with the normal phosphorus treatment, andreach significant difference level between varieties, that of YushuNO.1 and Chengshu104 increased mostly and were P-tolerantgenotypes. The contents of MDA were increased under low P stress,that of Yidianhong increased mostly and were P- sensitive genotypes.As the fall in the levels of phosphorus, showing lower chlorophyllcontent. Study photosynthesis and Chlorophyll fluorescenceparameter of different Broomcorn millet genotypes, The resultsshowed that net photosynthetic rate (Pn), transpiration rate (Tr) andstomatal conductance (Gs) were decreased under low P stress. whileintercellular CO2concentration (Ci) do not reach differences. Initialfluorescence（Fo）and the cancellation of the photochemical destroycoefficient (NPQ) were increased, but（Fv）,（Fm）,（Fv/Fm）and（qP）were decreased under low P stress. Grain numbers per plant,1000-grain weight and yield were decreased under low P stress in maturity stage, and Yushu NO.1 was more than Yidianhong, 50.43%,10.37% and 85.26%, respectively. This showed Yushu NO.1 wasP-tolerant genotype, and Yidianhong was P- sensitive genotype.The relevant analysis indicated that the relevance between rootlength, root shoot ratio , and SOD activity, POD activity, MDA contentand CAT activity are positive correlation in each period . Chlorophyllcontent and photosynthetic rate(Pn), transpiration rate(Tr) arepositive correlation in jointing stage and heading stage. Through themultivariate linear regression analysis results showed that plantphosphorus efficiency related total P contents. A dendrogram ofphoto generated from plant height，root shoot ratio, root length, totalbiomass, total P contents results showed that phosphorus efficiencyof Yushu NO.1 is highest; and that of Yidianhong and Chengshu95 arelowest; that of Chengshu104 , Jinshu NO.2 and Jinshu NO.3 aremoderate.(3)Using the water culture method, the biomass, nutrientcharacteristics of phosphorus and the biological responses of rootsystem of three broomcorn millet varieties (Yushu NO.1, Jinshu NO.2,Yidianhong) under the P-deficiency condition were researched. Theresult showed that P uptake efficiency is the main contributor to Ptolerance at low phosphorus stress, and the relative P content inYushu NO.1 (P-tolerant genotype)and Jinshu NO.2 (P-middle type) arehigher than that in Yidianhong (P-sensitive genotype). Thesebroomcorn millet genotypes were characterized by chlorophyllcontent, root activity and apase activity, showing lower chlorophyllcontent, but higher root activity and apase activity. In seedling stage,Yushu NO.1 variety has obvious advantage. Moreover, Under the phosphorus deficiency the drymass lowered remarkably, and thephosphorus deficiency affected shoot drymass accumulation. Theresults suggest that three broomcorn millet varieties have differentstrategies to adapt the low P stress environment by coordinating rootmorphological and physiological plasticity.