Ecophysiological Mechanisms Of Forage Shrubs Resistant To Drought&Cold In Karst Areas

Southwest karst mountainous area in China is the core distribution area in Eastern Asia of the world karst, its basic features are harsh habitat and ecological fragility, the severity of the habitat is highly concentrated expression of the high rate of bare rock, the soil is shallow and sporadic, inadequate supply of water and nutrients, and the ability to hold is poor; the presentation of fragility to environmental capacity is small, the capacity of land carrying is low, the anti-interference ability is weak, and the recovery after natural disturbance is slow and difficult. Although karst mountain area is located in Humid subtropical climate zone, because of the karst mountains are mainly distributed in the Yunnan-Guizhou Plateau, low-lying areas occurs seasonal drought frequently and high altitude chilling injury occurs frequently in winter. Guizhou Province as the core distribution area in Chinese karst area, since the implementation of the grassland ecosystem, promoting the feeding patterns of black goat with shrub grassland breeding, however, due to seasonal drought and chilling and other reasons, it entails to be selected suitable anti-drought or anti-cold shrub varieties in local areas to generalized application. In this study, four kinds of common shrubs in arid areas (Indigofera pseudotinctoria Mats、Leapedeza bicolor Turcz、Amorpha fruiticosa Linn and Indigofera amblyantha), seven kinds of shrub commonly used in cold regions (Sophora davidii, Indigofera amblyantha, Robinia pseudoacacia L., Semen Cajani Cajani, Radix Dodonaeae Viscosae, Cassia) were chosen to be test materials; Using field observations, laboratory analysis and mathematical statistics and other methods to do stress research, as the following conclusions:The growth of height and Leaf area of Indigofera pseudotinctoria Mats、Leapedeza bicolor Turcz.、 Amorpha fruiticosa Linn and Indigofera amblyantha were inhibited significantly under water stress, along with the increasing time and degree of water stress, the degree of inhibitory increased. With the increasing degree of water stress, the relative water content of leaves of the four seedlings decreased.(2) With the increasing time of water stress, the trend of Chlorophyll a content and Chlorophyll b content of Indigofera pseudotinctoria Mats、Leapedeza bicolor Turcz.、Amorpha fruiticosa Linn and Indigofera amblyantha emerged first, and then decreased. The ratio of Chlorophyll a to b changed slowly at the early stage of stress treatment, then decreased substantially, and had a small increase at the later stage of stress treatment. To the later stage of stress treatment, Chlorophyll a, Chlorophyll b and the ratio of Chlorophyll a to b of Amorpha fruiticosa Linn had a minimum decline compared with the early stage of stress treatment, follwed by Leapedeza bicolor Turcz, and Indigofera pseudotinctoria Mats is the maximum. With the increasing time of water stress, the Proline content, Soluble sugar content and Soluble protein content of four shrubs showed an upward trend. The Soluble protein content decreased while the increasing degree of water stress. The trend of Proline content and Soluble sugar content increased slowly in different stage of stress treatment.(3) With the increasing degree of water stress, the Malondialdehyde content and the relative electrical conductivity rate showed an upward trend. With the increasing time of water stress, the trend of these increased slowly at the early stage of stress treatment,but had a significant increasing trends in the end. Severe stress Indigofera amblyantha, and Indigofera pseudotinctoria Mats conductivity were severely injured, resulting in a large number of extravasation of intracellular ion, which caused that conductivity, respectively,6.90,6.68times; While Amorpha fruiticosa Linn and Leapedeza bicolor Turcz only control in severe stress late1.97times and2.00times, indicating that Amorpha fruiticosa Linn and Leapedeza bicolor Turcz osmotic adjustment ability than the other two shrubs. The activities of SOD, POD, CAT activity in the four shrubs at a higher level showed a different enzyme activities in the different treatment process, and they maintain a certain degree of complementarity. With the increasing degree of water stress, the trend of SOD, POD and CAT activity of three shrubs emerged first and then decreased, while Amorpha fruiticosa Linn maintained an upward trend all long. However as increasing time of water stress, those of less tolerant shrubs firstly appeared a declining trend.(4) Indigofera pseudotinctoria Mats、Leapedeza bicolor Turcz.、Amorpha fruiticosa Linn and Indigofera amblyantha, there are differences in the diversity of species in drought resistance on the performance of several drought indicators listed. Strengths and weaknesses of different indicators to identify the different shrubs from drought inconsistent, indicating that they take different adaptive mechanisms to drought stress. Through the method of subordinate (anti-subordinate) function, comprehensive assessment on the drought resistant index of four shrubs indicated that the order of drought resistance capability of four shrubs was Amorpha fruiticosa Linn> Leapedeza bicolor Turcz> Indigofera pseudotinctoria Mats> Indigofera amblyantha.(5) Cold resistance tests on seven candidates shrubs (Sophora davidii, Indigofera amblyantha, Robinia pseudoacacia L., Semen Cajani Cajani, Radix Dodonaeae Viscosae, Cassia glauca Lam and Crotalaria), its hardiness level were strong cold resistance (Sophora davidii, Indigofera amblyantha, Robinia pseudoacacia L.), medium cold resistance (Semen Cajani Cajani and Radix Dodonaeae Viscosae) and poor cold resistance (Cassia glauca Lam and Crotalaria).(6) To the later stage of low temperature stress, Chlorophyll content of Sophora viciifolia and Robinia pseudoacacia are great than other shrubs, the weakest is Dodonaea viscose and Cassia alata Linn.; Under low temperature stress, the MDA content of Crotalaria is higer, while the MDA content of Sophora viciifolia and Robinia pseudoacacia were lower.(7) Under low temperature stress of7kinds of shrubs’activity of antioxidant was different and the antioxidant enzymes activity was limited. The less tolerant shrub’s(crotalaria) activity of antioxidant was lower, The tolerant shrub’s (Sophora viciifolia、Robinia pseudoacacia) activity of antioxidant was higher. Using the methods of subordination and counter-subordination function, we can get a comprehensive assessment of cold resistance, the cold resistance order is Sophora viciifolia>Robinia pseudoacacia> Indigofers amblyatha> Dodonaea viscose> Cassia alata Linn> pigeonpea> crotalaria.