Effects Of Heavy Metal On Seed Germination And Seedling Physiological Growth Of Two Warm-season Turfgrasses

In order to solve the problem of heavy metal pollution in soil of Nanchong City,Cynodon dactylon and Paspalum notatum seeds were selected as experimental materials.Four concentration gradients of Cu²⁺,Zn²⁺and Pb²⁺solutions were used for single or combined treatment,and then germination test was carried out in seed incubator.The germination ability,seedling root length and seedling length,chlorophyll content,antioxidant enzyme activity and injury index of two turfgrasses were measured on the21st day.The effects of heavy metal stress on Seed Germination and seedling growth of turfgrasses were studied,and the tolerance and resistance of two warm season turfgrasses to different heavy metals were analyzed.The results will provide a basis for the selection of grass species in the remediation and management of heavy metal contaminated soil.The main results are as follows:（1）The effects of heavy metal stress on Seed Germination of two turfgrasses were significantly different（P<0.05）.The tolerance range of Cu²⁺+Zn²⁺to C.dactylon and P.notatum was 0-200mg/L,but the tolerance range of Cu²⁺and Cu²⁺+Pb²⁺to C.dactylon was greater than that to P.notatum（0-400mg/L for C.dactylon and 0-200mg/L for P.notatum）.The tolerance range of C.dactylon and P.notatum to Pb²⁺and Zn²⁺+Pb²⁺was0-800mg/L,but the tolerance range of C.dactylon to Zn²⁺was greater than P.notatum（C.dactylon:0-800mg/L,P.notatum:0-400mg/L）.（2）Heavy metal stress had significant effect on the growth of two turfgrass seedlings（P<0.05）.The root length and seedling length of the two turfgrasses were inhibited under heavy metal stress(except that Pb²⁺=100mg/L C.dactylon root length was promoted).When Cu²⁺and Cu²⁺+Pb²⁺≥200mg/L,Zn²⁺+Pb²⁺≥800mg/L,C.dactylon appeared rootless seedlings,and had roots under other metal stress,but with the increase of concentration,the root length shortened and became thicker,and was black and transparent.However,P.notatum was rootless under Cu²⁺and Cu²⁺+Zn²⁺stress,and rootless under Zn²⁺,Cu²⁺+Pb²⁺≥200mg/L and Pb²⁺≥800mg/L.As far as root length is concerned,heavy metal stress has more obvious inhibitory effect on the root growth of P.notatum.（3）Heavy metal stress had effect on chlorophyll content of two turfgrasses.Under the stress of Cu²⁺,Zn²⁺,Pb²⁺,Cu²⁺+Pb²⁺,Zn²⁺+Pb²⁺,chlb of C.dactylon first increased and then decreased with the increase of treatment concentration.Chla and chlb of C.dactylon reached the maximum when the concentration of Cu²⁺,Zn²⁺,Pb²⁺was 100 mg/L,and Chla and chlb reached the maximum when the concentration of Cu²⁺+Pb²⁺、Zn²⁺+Pb²⁺was 200 mg/L;Chla and chlb decreased with the increase of Cu²⁺、Zn²⁺、Cu²⁺+Zn²⁺、Cu²⁺+Pb²⁺、Zn²⁺+Pb²⁺stress concentration of P.notatum,showing obvious inhibitory effect.（4）Under heavy metal stress,the antioxidant enzyme systems of two turfgrasses were activated.The phenomenon of"low concentration promotes,high concentration suppresses".（5）The cell membrane of two turfgrasses was damaged by heavy metal stress.The damage degree of cell membrane of two turfgrass increased with the increase of stress concentration.In conclusion,heavy metal ions had effects on Seed Germination and seedling growth of two turfgrasses,and the overall effect trend was low concentration promoting and high concentration inhibiting.However,C.dactylon had stronger resistance and tolerance in Cu²⁺,Zn²⁺,Pb²⁺,Cu²⁺+Zn²⁺,Cu²⁺+Pb²⁺environment than P.notatum,and P.notatum was stronger than C.dactylon in Zn²⁺+Pb²⁺environment.