Effects of Ca on growth and some physiological characteristics of maize under Cd stress

Nutrient solution culture experiment was conducted to study effect of Ca on plant growth, chlorophyll , malondialdehyde concentration and activities of nitrate reductase, ATPase , superoxide dismutase (SOD), ascorbate peroxidase (AsA POD), guaiacol peroxidase and catalase (CAT) in maize (Zea mays L.) under Cd stress The results showed that: (1) Plants under Cd stress showed wilt, chlorosis, necrosis in leaves and black in roots; biomass of shoots and roots without Ca supply combining Cd stress strongly decreased The addition of Ca to solution could increase the biomass of plants and alleviated the Cd toxicity Plants with foliar application CaCl2 still had the symptom of Cd toxicity and low biomass weight (2) With the addition of Cd to solution, Cd concentration in roots and shoots of maize increased significantly and Cd concentration in roots were more than shoots Ca depressed the translocation of Cd from roots to tops of maize, but had no apparent effect on the absorption of Cd by roots because the concentration of Cd in roots of maize had little difference between the treatment without Ca supply combined Cd and the treatment with Ca supply combined with Cd Whereas Cd concentration in shoots with Ca supply were higher than those without Ca supply Foliar application CaCl 2 four times could increased Cd concentration in shoots compared with foliar application CaCl 2 two times (3) The contents of chlorophyll a , chlorophyll b and total chlorophyll in leaves of maize without Ca supply decreased Cd addition also markedly decreased the chlorophyll pigments and increased Chl a/Chl b ratio Chlorophyll content in leaves were significantly enhanced by Ca supply to roots in solution containing Cd Foliar application CaCl 2 couldn't prevent effect of Cd on chlorophyll in leaves Stopping Ca supply and adding Cd to solution or stopping Cd supply and adding Ca to solution partly reduced effect of Cd on chlorophyll in leaves (4)The activities of nitrate reductase in leaves and ATPase in roots of maize were inhibited by the treatments without Ca or with Cd supply, especially in those leaves under combination stress without Ca and Cd supply Whereas the activities of nitrate reductase in leaves and ATPase in roots of maize under Cd stress were enhanced by Ca supply (5) In those leaves and roots of maize without Ca supply, the activities of ATPase and endogenous oxygen radicals scavenging enzymes systems including SOD, AsA POD, guaiacol POD and CAT were higher than those of plants with such treatments as Ca supply continuously, stopping Ca supply adding Cd ,stopping Cd addition and resupply Ca concentration of malondialdehyde in leaves also remain pronounced levels Foliar application CaCl2 couldn't weakened the effect of Cd on endogenous oxygen radicals scavenging enzymes systems and malondialdehyde in plants, however increased the activities of ATPase in leaves In conclusion, Ca supply in root could alleviated Cd toxicity on growth, chlorophyll content and the effects of Cd on the activities of nitrite reductase , ATPase and endogenous oxygen radicals scavenging enzymes systems such as SOD, AsA POD, guaiacol POD and CAT in maize