Two Cultivars Of Peanut (Arachis Hypogaea) Seedlings Show Different Tolerance To Calcium Deficiency

Calcium （Ca） is an essential nutrient with key structural and signalling roles for plant growth anddevelopment.Ca deficiency can reduce crop quality and yield. Peanut （Arachis hypogaea） is sensitive toCa deficiency. The objectives of this research were to determine Ca uptake and transport of two peanutcultivars grown in nutrition solution and to reveal possible causes of their different tolerance to Cadeficiency. The two peanut cultivars including LH11and YZ9102were selected. Seedlings at the firstleaf stage were transplanted in nutrient solution with different Ca treatments, respectively. The Fouriertransform infrared spectral （FTIR） was used to analyze component in different parts of peanut andcompared the spectral data. The root images were obtained with a scanner and analyzed by WinRhizosoftware. Ca²⁺fluxes in different root zones were measured non-invasively using the scanningion-selective electrode technique. The experiment of kinetics uptake was done with the intact roots oftwo-week-old seedlings under external Ca（NO3）2concentrations in the range0.02to0.50mmol/L.Localization and distribution of Ca²⁺in cells of and shoot tips were observed by electron microscopiccombined with potassium pyroantimonate technique. The main results and conclusions weresummarized as followings:（1） Under0and0.01mmol/L Ca supplies, peanut cultivar YZ9102did not appear Ca deficiencysymptoms and plant biomass did not change, whereas LH11appeared necrosis in shoot tip, lost apicaldominance with more lateral branches from shoot bases, and plant dry matter weights decreasedsignificantly. YZ9102had higher plant Ca concentration and Ca accumulation than LH11. Thepercentage of root Ca accumulation in total plant Ca uptake was higher in LH11than YZ9102, whilemore Ca distribution to leaves of YZ9102. Compared with2.00mol/L Ca treatment, LH11plants withCa deficiency showed higher transmittance at peaks1060,1380,1655,2922, and3420cm-1in FTIRspectra, indicating that the contents of protein, lipid and sugar decreased obviously in LH11plantssubjected to limited Ca supply. However, the FTIR spectra of YZ9102were less affected by Cadeficiency.（2） Under2.0mmol/L Ca treatment, Ca-antimonate precipitates in root cells were principally locatedin cell wall, vacuole, vacuolar membrane and intercellular space. The cellular structure of rootsremained intact under electron microscopic observations. When the Ca was insufficient supply,Ca-antimonate precipitates of root cells were mainly distributed in the cytoplasm, nucleus, and thespaces between plasma membrane and cell wall. Ca stress resulted cell spacing larger, disruption ofcytoplasm, organelle disintegration. Under0.01mmol/L Ca treatment, LH11shoot tip cells showedmore swelled chloroplasts and had less Ca-antimonate precipitates than YZ9102.（3） The lengths of roots with diameter0.15⁰.45mm and>0.45mm in LH11plants were significantlyreduced by limited Ca supply, but did not change in YZ9102. Michaelis-Menten function was used todescribe Ca²⁺uptake kinetics by intact roots. The estimated parameter Kmvalues were7.75mmol/L forLH11and5.27mmol/L for YZ9102. Vmaxvalues were17.54μmol/g·h for LH11and18.24μmol/g·h forYZ9102. YZ9102had a higher Vmaxand lower Kmthan LH11. （4）When plants were grown in inadequate Ca regimen, net Ca²⁺influxes appeared in the zones of200μm from root apex of LH11and net Ca²⁺effluxes was in the zones of200¹500μm from root apex ofLH11, while YZ9102roots maintained stable net Ca²⁺influxes.It is suggested that peanut cultivar YZ9102seedlings showed longer root length and higher capacitiesof Ca uptake and Ca translocation to shoots than that of LH11in response to Ca deficiency stress, whichmight be account for higher tolerance of YZ9102to Ca deficiency compared with LH11.