Study On The Drought Resistance Of Four Important Shrubs Seedlings Applying To Rock-slope Afforestation

Four shrubs,Lespedeza Formosa, Indigofera pseudotinctoria, Cassia corymbosa, Amorpha fruticosa, which grow well on rock slopes, were chosen as experimental materirals and studied with natural drought stress of four lasting drought stages and subsequent watering for their drought resistance, in regards to leaf water status, antioxidase activity, osmotic substances and photosynthetic status, etc., learning their drought resistance mechanism and supplying scientific basis for choosing rock slope afforesting plants in Zhejiang province and nationwide.Conclusions were as follows: (1)Under water stress, height growth of these four shrubs were inhibited seriously. Root-shoot ratio was increased and beyond one indicating strong competence capability. Morphological exhibition showed that the longer the stress was, the worse the damage was. All species recovered in varied extent after watering again. Cassia corymbosa was subjeced to the least damage and got the best recovery, while several seedlings of Lespedeza Formosa were damaged to die.(2)Leaf relative water content (LRWC) decreased significantly under water stress and increased after watering again.Under water stress, water satuation deficit (WSD) was arranged as: Lespedeza Formosa> Indigofera pseudotinctoria> Cassia corymbosa> Amorpha fruticosa, and after watering again changed to Amorpha fruticosa> Indigofera pseudotinctoria> Lespedeza Formosa > Cassia corymbosa, indicating different capacity of dissipation and absorbance. Cassia corymbosa showed the best leaf water conservation (LWC), Indigofera pseudotinctoria and Amorpha fruticosa in the second place, and Lespedeza Formosa the last. (3) Under water stress, superoxide dismutase (SOD) activity of Lespedeza Formosa and Indigofera pseudotinctoria increased insignificantly under light water stress and significantly later; SOD activity of Cassia corymbosa and Amorpha fruticosa increased significantly at first and then decreased significantly. Peroxidase (POD) activity of these four shrubs showed a same trend that was increased firstly and then decreased under water stress and increased after watering again. POD activity was always arranged as: Cassia corymbosa > Amorpha fruticosa> Indigofera pseudotinctoria> Lespedeza Formosa. Content of malondialdehyde (MDA), soluble sugar (SS) and Proline (Pro) increased generally under water stress. Cassia corymbosa could maintain low MDA content for a longer time, showing better ability to clear Lipid Peroxidation. Lespedeza Formosa with most proline changing range showed worse drought-resistance than Cassia corymbosa with least changing range. After watering again, all of these drought-resistance indexes trended to normal level with significant changes. (4) Photochemical processes of these four shrubs were damaged under water stress, resulting in lower net photosynthetic ratio, narrower light adaptation ranges, and smaller light using efficiency. After watering again, all photosynthetic parameters tended to be normal, which showed that the damage caused by drought was reversible. Indigofera pseudotinctoria and Cassia corymbosa exhibited better than Lespedeza Formosa and Amorpha fruticosa. (5) Relative analysis showed great relationship between drought-resistance indexes and soil water content. Inherent links among these drought-resistance indexes were also complicated. By the method of vague mathematical jurisdiction analysis, the drought resistance ability of these four shrubs was Cassia corymbosa> Lespedeza Formosa>Indigofera pseudotinctoria > Amorpha fruticosa.