| Panax.notoginseng (Burk.) F.H.Chen, which belongs to the genus Panax of the family Araliaceae, is grown in Baise of Guangxi province. It is a kind of rare Chinese medicinal materials. Early investigation showed that the seedling cracking root (SCR) in the P. notoginseng regions wasprevalent, and it had serious influence on yield and quality of P. notoginseng.The causes of this phenomenon, the relationship of SCR and rhizosphere microorganisms, the influence of SCR to the growth of P. notoginseng and the preventionare studied. The results are showed as follows:1. P. notoginseng SCR was mainly happened in the period of rapid enlargement of seedling roots (Jun. to Oct.) In the beginning, some points of brown spots were appeared in the integration, and then connect into strips, cracking was occurred gradually, and the root shrinking, the leaves turned yellow.2. P. notoginseng SCR is a physiological disease. Spots of SCR were used to isolation of pathogenic fungi, any of pathogenic fungiwere not been found. The bacteria from SCR was inoculated back to healthy root, and the SCR did not occur. Parenchyma cellsof SCR were observed by microscope, and there was not bacteria be found. The reasons of this disease had not relationship with infectious biological factors, but caused by the external environment, for temperature, humidity, rainfall, rainfall time, altitude, soil physical properties. In addition, epidermis cells of root arranged closely may lead to SCR.3. Soil microbes are different that if there planting P. notoginseng before or not. Initial stage of SCR happened, the soil microbes were not changed significantly, later, root was cracked, nutrients from root infiltrated out, a large number of fungi, bacteria and actinomycetes reproduction, resulted in antagonistic action, and SCR was influence.4. Agronomic characters, the content of mineral element, photosynthesis, physiological and biochemical indexes, content of endogenous hormones were changed significantly when the disease appeared. Compared to the healthy root, diameter and length of root were reduced 27.91 and 62.69%, fresh weight, dry weight and drying rate were reduced 40.18,59.09 and 14.3% respectively. The fresh weight and dry weight Above-ground reduced 35.85 and 37.50%. The content of mineral elements had large changed, Cu, Mn, Zn, Ga, Mg, B, K and N reduced 1329.38,472.65,261.13,212.50,187.41,141.77,22.00 and 35.71%, respectively. Si, P, Mo increased 27.87,4.55 and 70.83%, respectively. The content of chlorophyll, net photosynthetic rate, the stomatal conductance, transpiration rate, carbon dioxide concentration of intercellular and other Photosynthetic characteristic index were reduced. The protein of plant, lignin, cellulose and root activity were reduced 13.20,74.55,216.67 and 61.9%. Polysaccharide was increased 8.28%. The content of GA and ZR in the inner layer and outer layer of root, leaves, the content of 6-BA in root, the content of ABA and IAA in the inner layer and leaves, when compared to the healthy plant, the illness were higher. The content of 6-BA in leaves, ABA and IAA in the outer layer of root, the healthy plant were higher.5. It can not be recovered when the root cracked, for this issue, putting prevention first is the only way. In addition to improving the cultivation environment, more potash and calcium and other fertilizer can reduce root cracking significantly. Growth regulator, such as 10mg/L GA3,900mg/L PP333, 100mg/L 2,4D also can reduce root cracking. |
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