Screening And Study On Morphological And Physiological Characteristics Of Soybean Varieties (Lines) Tolerating To Low Potassium

Four types are classified according to the different yields and responses to low potassium of eighty soybean varieties, which are planted in low potassium soil with two K levels, i.e. high yield and sensitive (HS); high yield and insensitive (HI); low yield and sensitive (LS) and low yield and insensitive (LI). In these types, HI and LI are the varieties (lines) tolerating to low potassium. Then a pod experiment is conducted with two K levels to evaluate the difference of the main morphological and physiological indexes of each typical variety selected from those four types. The morphological indexes include plant height, leaf area, the length of the main root, the quantity of the first branched root, the length of the longest branched root, the root volume and the dry weight of root and plant, et al. The physiological indexes include the chlorophyll content, the photosynthesis rate, the root vigor, the active and total uptake areas of the root, the malondialdehyde (MDA) content, the activities of super oxide dismutase (SOD), catalase CAT) and peroxidase (POD), et al. The results are as follows:1. Screening of soybean varieties tolerating to low potassiumThe practice shows that planting different soybean varieties in the K deficient soil with different K levels is an available and effective way to classify the tolerance ability of these varieties to low potassium stress. The experiments has screened some typical varieties of each type, such as Tiefeng 31, 95180A-5, GD584, GD1980 belong to HS, Shennong 6, GD2730, Jiunong 22, 95130A-10 belong to HI, Tie 95068-5, GD2605, Tiefeng 29 belong to LS, GD584, GD2989, GD2331 belong to LI, in which the HI and LI are the varieties tolerating to low potassium.The symptom of K-deficiency is very obvious for different varieties in the field. The insensitive has little or no symptom, but the sensitive' symptom are very heavy.2. The response to low potassium stress of four types (1) The difference of morphologyThe low potassium stress has a negative effect on the plant height and the leaf area of each type. The plant heights and leaf areas of the sensitive decrease more obviously than those of insensitive. And the length of the main root alsodecreases, so the depth of root up-taking nutrition from the soil is decreased. Compared with the length of the main root, the quantity of the first branched root and the length of the longest branched root are all lengthened on the stress of low potassium, so the uptake breadth and strength of the root are much higher than that of CK. On the other hand, the dry weights of the root and the plant are decreased on the low potassium stress, but it's not obvious between the sensitive and insensitive.(2) The difference of physiologyThe chlorophyll content of the sensitive decreases more obviously than that of the insensitive when stressed by low potassium, which decreases the assimilation of energy from sunlight and declines the yield. The photosynthesis rate of each variety is affected by the low potassium stress in great extent, and the photosynthesis rate of leaf in low K treatment is lower than that of CK. There is less difference in the sensitive and the insensitive, and there is no obvious effect to the yield of different types.The root vigor can be stimulated on the low potassium stress at the seedling, but be weakened at the pod stage, which is embodied more obviously in the varieties of low yield than those of high yield, and in the sensitive than the insensitive.Assembly to the change of root vigor, the root active uptake area and total uptake area are also stimulated on the stress of low potassium in some extend, but the range and appearance time are different among varieties (lines). As a word, the active uptake area and total uptake area of the insensitive are much larger than that of the sensitive, but the change range of the insensitive is less obviously than that of sensitive in two treatments.The low potassium stress can harm the cell membrane in some extend, and the malondialdehyde (MDA) content of the sensitive is much higher than that of the insensitive, especially in the special period when the plant need potassium extremely, which shows that the low potassium stress on the sensitive is heavier than that of the insensitive, and the cells' lipid bilayer of the sensitive is harmed more seriously than that of the insensitive.As the protective enzyme systems of the plant cell, super oxide dismutase (SOD),...