Physio-biochemical Responses And Bioaccumulation Of Jatropha Curcas L. To Caesium And Strontium Stress

The experiments were performed by using Jatropha curcas L. asmaterials, cultured in loam and sandy soils respectively, as followed:（1）Stress by different concentration of¹³⁴Cs⁺and⁸⁸Sr²⁺respectively （bothfor100mg/kg,200g/kg,400mg/kg）;（2） Stress by combination of¹³⁴Cs⁺and⁸⁸Sr²⁺(100¹³⁴Cs⁺+100⁸⁸Sr²⁺mg/kg,200¹³⁴Cs⁺+200⁸⁸Sr²⁺mg/kg);（3）Stress under200mg/kg¹³⁴Cs⁺with K⁺（35mg/kg、70mg/kg）added, andStess under200mg/kg⁸⁸Sr²⁺with Ca²⁺（100mg/kg、200mg/kg）added.Each treatment was sampled after30d,70d and120d respectively, anddata including growth index, physiological and biochemical index, aswell as accumulation index were detected. The results were shown asfollowed:1、 Under¹³⁴Cs⁺stress in different concentration, the height, stemdiameter, leaf area and organization water content of J. curcasseedlings decreased with¹³⁴Cs⁺concentration increased. Easpeciallyunder high stress400mg/kg, some leaves turned yellow and falled off.These indicated that J. curcas seedlings could grow in eachconcentration treatment, but the growth was inhibited obviously underhigh¹³⁴Cs⁺stress. Except for the control, there were negativerelationships with stress concentration or time and content of contentChla, Chlb and Chla+b of J. curcas seedlings in all treatments.Thefluorescence parameters Fv/Fm （0.8⁰.84） is in a normal fluctuations ina range of Cs+concentration0²00mg/kg, and changed insignificantly.But in high concentration of400mg/kg conditions, they were decreasedobviously with stress time increasing. It showed¹³⁴Cs⁺stress of highconcentration has obvious stress effect to photosynthetic capacity of J.curcas seedlings, and stress level increased with stress time increasing.The maximum relative electronic transfer rate （ETRm a x） and half ofsaturation light strong （IK） decreased with stress concentration and timeincreasing. It showed electronic transfer rate and light tolerance abilityof J. curcas seedlings became weak under stress. Fast light curve initialslope of lamina （α） of J. curcas seedlings decreased obviously in each of treatments compared with control. It showed that ability to capturelight was suffered by stress. In addition, content of MDA, Pro andconductance of J. curcas seedlings increased with concentrationincreasing. It showed stress increasing could influence relativepermeability of membrane of blade, and caused heavier damage. Plantleaf answered oxidative damage mainly by improving antioxidantenzymes activity, such as peroxidase （POD）, superoxide dismutase（SOD） and catalase （CAT） and so on. Compared with loam soil culture,in each of stress concentration, seedlings growth were more weak insandy soil than that in loam soil, and the plant height is only1/3¹/2compared to that of the loam medium. And chlorophyll content andfluorescence parameter values of seedlings were lower in sand soil,while fluctuation range of antioxidant enzymes were larger. In addition,⁸⁸Sr²⁺stress in different concentration, the changing trends ofphysiological and biochemical indexes of J. curcas seedlings was thesame as those of¹³⁴Cs⁺stress, such as growth index, light andphysiological indexes, antioxidant enzymes and osmoregulation and soon. However the growth, photosynthetic capacity of J. curcas seedlingswere restrained with⁸⁸Sr²⁺stress concentration increasing and stresstime prolonging. On the contrary, the membrane permeability andantioxidant enzymes activity of blade enhanced.⁸⁸Sr²⁺stress in lowconcentration （0²00mg/kg） influenced on each index of J. curcasseedlings insignificantly. It showed J. curcas seedlings had strongadaptability to⁸⁸Sr²⁺stress in range of0²00mg/kg. High⁸⁸Sr²⁺stress（400mg/kg） significantly reduced content of Chla, Chlb, Chla+b,carotenoids （Car） and photosynthetic fluorescence parameters of J.curcas seedlings with stess time increasing, and significantly improvedcontent of MDA, Pro and specific conductance. It showed that⁸⁸Sr²⁺stress of high concentration was obviously to J. curcas seedlings, andresisted to oxidative damage by enhancing POD, SOD and CAT enzymeactivity. Furthermore, data showed that, J curcas seedlings weredamaged smaller in loam soil than in sandy soil under the sameconcentration of Sr²⁺stress. It was the similar stress tends between ¹³⁴Cs⁺and⁸⁸Sr²⁺composite and single treatment to growth,photosynthesis, osmoregulation and antioxidant system of J. curcasseedlings. The high concentration stress was more obvious on J. curcasthan low concentration to inhibit growth and physiological function.2、 The treatments of¹³⁴Cs⁺stress with K⁺added and⁸⁸Sr stresswith Ca²⁺added could reduced the stress damage on J.curcas seedlingsin some extent. Expecially in lower concentrations of K⁺and Ca²⁺added, the height and biomass increased obviously. Under¹³⁴Cs⁺stresswith K⁺, Fv/Fmand α increased firstly and then dereased gradually, aswell as Chla、 Chlb and Chla+b increasing. Under⁸⁸Sr stress with Ca²⁺,Fm and Fv/Fm became higher than that under the single stress of⁸⁸Sr²⁺,which indicating that the photosynthetic capacity was suffered. Thecontent of Pro reduced obviously after adding the K⁺or Ca²⁺, whichindicating that the osmotic stress on leaves of J. curcas declined. Whilethe ability to relief stess by K⁺and Ca²⁺may reduce under highconcentration. In addition, soil properties may affect the ability torelief stess under¹³⁴Cs⁺and⁸⁸Sr²⁺by K⁺and Ca²⁺respectively.According to most of the data, the ability to relief stess by K⁺and Ca²⁺may improved more in loam soil.3、 The enrichment of¹³⁴Cs⁺and⁸⁸Sr²⁺by J. curcas seedlings wereincreased with increasing of concentration and tme. Root was the majorenrichment organs, and the ability sequence of enrichment were root>leaf> stalk.The highest¹³⁴Cs⁺enrichment in root was12.38mg.g-1andthe highest⁸⁸Sr²⁺enrichment in root was24.41mg.g-1. In all treatmentsampling, the transshipment coefficient and the enrichment coefficientof the J. curcas root, leaf and stalk were positive correlativity withtime, and the sequence was L/R＞S/R and R/S＞L/S＞S/S. The contentsof¹³⁴Cs⁺and⁸⁸Sr²⁺in J. curcas seedling root, leaf and stalk reducedadding K⁺and Ca²⁺. And adding lower concentrations of K⁺and Ca²⁺,the enrichment of¹³⁴Cs⁺and⁸⁸Sr²⁺reduced more obviously. The¹³⁴Cs⁺content and enrichment coefficient of J.curcas were lager in sandy soilthan those in loam, and the¹³⁴Cs⁺content in J. curcas decreased withthe increasing of K⁺. In addition,⁸⁸Sr²⁺contents of J. curcas in sandy soil were lager than those in loam, which indicating that Ca²⁺mightinhibit the absorbtion of Sr²⁺to some extent. The Ca²⁺in lowconcentration could improve seedlings growth stalk thick. However theeffects of high concentration Ca²⁺were unobvious.