Effects Of Cd,Cu,Pb On The Germination And Seedling Growth Of Wheat

With the development of our country's economy and the improvement of people's living standards,heavy metal pollution in the environment has becoming more and more serious.As wheat is an important food crop in China,therefore,it is of long-term practical significance to study the influence of heavy metals on wheat.In the study,the effects of heavy metals such as cadmium(Cd),copper(Cu),and lead(Pb)on wheat's seed germination,seedling growth,chlorophyll,physiological and biochemical characteristics,roots' micro-structures and cell wall composition.To provide a basis for exploring the toxic mechanisms of heavy metals on wheat,the main results are as follows:(1)Cd affects the growth,physiological and biochemical processes of wheat seedlings and cellular components of roots.Cd concentration of 0.1 mg/L had little effect on seed germination and growth,and even had a certain promoting effect.Cd concentration of 100 mg/L inhibited the germination and growth of wheat,especially inhibited root growth.Wheat has reduced chlorophyll a,chlorophyll b,chlorophyll a+b,and carotenoids.The content of malondialdehyde(MDA)increased,and the content of superoxide dismutase(SOD)increased first and then decreased.The contents of peroxidase(POD)and catalase(CAT)increased in shoots and the content in roots decreased.After Cd treatment,the root cells become dense,the intercellular space is not fully developed,the shape of the cortical cells is irregular,the degree of primary woodization in the vascular column is low,the lumen of the catheter is small,the number increases,and the diameter of the root increases.Increased cellulose content.The tannins increase in the epidermis and cortex and decrease in the vascular bundles.Esterified pectin content increased significantly.Extensin content decreased.The content of galactan and arabin increased.The xylan content is reduced.(2)Cu affects the growth of wheat seedlings,physiological and biochemical processes and cellular components of roots.When Cu concentration was 1 mg/L,the growth of shoots was promoted.At 100 mg/L,seed germination and growth were inhibited.The contents of chlorophyll a,chlorophyll b,chlorophyll a+b and carotenoids decreased.After Cu stress,the contents of MDA and SOD increased,and the POD and CAT contents increased in shoots and decreased in roots.In terms of microstructure,Cu stress was consistent with Cd stress.The content of cellulose in the cell wall components is reduced.The tannin and pectin content increased.Both Extensin and galactans were increased.The content of arabinan and xylan increased first and then decreased.(3)Pb affects the growth,physio-biochemical process and root cell composition of wheat seedlings.Pb had no effect on seed germination and growth at a concentration of 0.1 mg/L,and was significantly inhibited at 1000 mg/L.The contents of chlorophyll a,chlorophyll b,chlorophyll a+b and carotenoids decreased.The MDA content decreased.With increased SOD content,POD and CAT content decreased in shoots and increased in roots.In terms of microstructure,it was consistent with the Cd and Cu stress.The cell wall contains more cellulose and tannins.Pectin content decreased.Extensin content increased.The content of galactan increased.The arabinan content increased.The xylan content increased.