Studies On Chromium And Lead Tolerance And Accumulation In Several Oil Crops

The tolerance and enrichment characteristics of four oil crops, including peanut （Arachishypogaea）, soybean （Glycine max）, sunflower （Helianthus annuus） and castor （Ricinuscommunis）, were studied under hydroponic culture treatment with different concentrations ofCr³⁺and Pb²⁺；Moreover, the antioxidant system and other physiological characteristics werealso investigated to study the effect of different concentration of Cr³⁺to the growth of peanut.The results in this study are as follows:1. The plant height, root length, shoot biomass, root biomass and tolerance index of thefour crops decreased in various degrees with the increase of Cr³⁺and Pb²⁺concentrations,shoot biomass of peanut and sunflower decreased relatively slightly and tolerance index ofboth crops was higher.2. The contents and accumulation of Cr and Pb in shoots showed increasing trend withthe increase of Cr³⁺and Pb²⁺concentration, and most of the heavy metal was accumulated inroots. Accumulation and translocation rate of Cr and Pb in peanut were relatively higher, theaccumulation of Cr and Pb in shoots of peanut under treatment of100mg·L^-1Cr³⁺and200mg·L^-1Pb²⁺was420.5and492.4μg·plant-1, respectively, while the translocation rate was23.1%and11.7%, respectively. The results indicate that peanut has both stronger toleranceand higher ability of enrichment under Cr³⁺and Pb²⁺stress, and could be used as a potentialcrop for the phytoextraction of Cr³⁺and Pb²⁺contaminated environment.3. The chlorophyll contents of four crops decreased with the increase of Cr³⁺and Pb²⁺concentration. Chlorophyll contents of peanut decreased relatively slightly. The prolinecontents in leaves increased under treatment of Cr³⁺and Pb²⁺. Proline contents in leaves ofpeanut, soybean, sunflower and castor were4.2,7.0,3.7and4.5times as much as controlunder treatment of200mg·L^-1Cr³⁺, and were7.1,10.5,4.6and5.3times under treatment of400mg·L^-1Pb²⁺. The lowering range of chlorophyll contents in peanut was smaller and theincrease of proline contents in leaves of sunflower was higher under Cr³⁺and Pb²⁺treatment,which indicate that both crops have stronger tolerance under Cr³⁺and Pb²⁺stress.4. Cr³⁺stress inhibited growth of peanut, lowered soluble protein contents of roots. Theactivities of antioxidant enzymes （SOD, POD, CAT） of peanut increased and then decreasedwith the increase of Cr³⁺concentration. Under treatment of200mg·L^-1Cr³⁺, the activities of the three enzymes wre1.5,1.4and2.2times as much as control in leaves, respectively.Compared with leaves, roots showed a greater variation in the activities of the three enzymeswhich indicate that roots had more stress under Cr³⁺stress.5. The contents of non-protein thiol （NPT）, GSH and phytochelatins （PCs） in leaves androots of peanut increased and then decreased with the increase of Cr³⁺concentration. Valuesof NPT, GSH and phytochelatins （PCs） content reached their maximum values in leaves undertreatment of200mg·L^-1Cr³⁺, and were1.51,1.36,1.36times as much as control, respectively;but those of roots reached their maximum under treatment of100mg·L^-1Cr³⁺, and were1.34,1.29,1.5times as much as control, respectively. Compared with leaves, NPT, GSH and PCscontents of roots decreased more under treatment of Cr³⁺.