Effects Of Different Calcium Content On Seedling Growth And Tipburn Occurring Of Chinese Chbbage

In order to understand the effects of calcium stress on seedling growth and tip burn occurring of heading Chinese cabbage(Brassica campestris L.ssp.pekinensis(Lour.)Olsson),Six cultivars of heading Chinese cabbage with different sensibility to calcium stress(10S04,10S10,10S36,10S157,10S237,10S327)were selected and sown in the perlite pot watered with modified Hoagland solution of different calcium concentration.There are four culture solutions with calcium content,of 96 mg,60 mg,30 mg and 0 mg were respectively designed and prepared for per plant in the seedling stage.Observe the growth status and tipburn disease index on time.Measure the biomass,roots activity,chlorophyll content,SOD,POD activity and MDA content on the fortieth day.The results are as follows:1.The all party of heading Chinese cabbage seedling was retarded under the low calcium stress condition,more inhibition in root than seedling,similar middle inhibition in leaf length and leaf width,little inhibition in leaf number.2.The degree of inhibition were increasing as low calcium stress increasing,On the basis of the fresh weight of seedlings cultured with calcium-deficient treatment.All the materials could be fall into three class:sensitivity type(10S10),medium sensitivity type(10S04、10S36、10S157、10S237)and hyposensitivity type(10S327),Their aerial parts biomass at calcium deficiency(0 mg)condition was dropped to 17.8%,30.7%-36.7%and 77.5%of full calcium condition respectively.3.The SOD,POD activity and MDA content in the leaf increase gradually as the calcium content decreasing in culture solution.The effect of low calcium stress on POD activity is more serious than MDA content and SOD activity.4.The chlorophyll content in the leaf and roots activity showed a downward trend as the calcium content decreasing in culture solution.They would be influenced significantly when the calcium content less than 30 mg and 60 mg per plant.5.The onset time and disease index of tip burn were earlier and higher as the calcium content decreasing in culture solution.The plants with calcium-deficient treatments were the most severe.6.The tip burn symptoms of six materials are mainly revolute or involute leaves,variegation,corrugate,chlorotic interior leaf,and the leaves of growing point dry up.But different symptom occur in different period or different materials.