喷施多效唑提高麻疯树幼苗耐盐性的生理机制

Physiological mechanism of foliage spraying paclobutrazol on increasing salt tolerance of Jatropha curcas seedlings

研究了600 mg/L PP333喷施对200 mmol/L NaCl胁迫处理下麻疯树幼苗干重、含水量、叶片细胞超微结构、光合作用、叶片渗透调节能力、叶片丙二醛含量和叶片抗氧化能力的影响。结果表明:600 mg/L PP333喷施处理能显著提高200 mmol/L NaCl胁迫下植株的干重、根冠比和叶片含水量,同时显著降低叶片电解质外渗率,降低叶片细胞超微结构的伤害程度,显著提高了其叶绿素含量、净光合速率、渗透调节能力、SOD酶活性和CAT酶活性,显著降低了MDA含量和POD酶活性。可见,PP333喷施能显著提高麻疯树幼苗对盐渍的适应,主要因为其提高了植株的抗氧化能力、光合作用、渗透调节能力。

Soil salinity is one of the major abiotic stresses with adverse effects on plant productivity and quality.As salt constantly accumulates in soil with irrigation,soil salinity becomes one of the greatest problems in agricultural production through out the world.Jatropha curcas,as the first referent tree in development of China biological diesel oil and a hotspot of the research in the world facing global energy crisis recently,has a very high environmental adaptation.However,few studies have been reported on the mechanism of salt adaptation and chemical regulation of the tree.Improvement of salt tolerance to utilize extensive salt soil is an important issue in both agricultural and biological sciences.Moreover,salt tolerance improved by chemical regulation used to be considered as an economic and effective method.Paclobutrazol（PP333） causes metabolic and structural changes in plant,and improves plant stress tolerance.Therefore,In order to evaluate the effects of foliage spraying PP333 on salt tolerance of J.curcas seedlings,the plant dry weight,root/shoot ratio,water content,the leaf cell ultrastructure,chlorophyll content,the photosynthesis,the osmotic adjustment ability and the antioxidation ability of J.curcas seedlings treated with 200 mmol/L NaCl for 10 d with foliage spraying in 600 mg/L of PP333 in greenhouse were investigated.The results obtained were as follows：（1） 200 mmol/L NaCl stress significantly decreased the seedling dry weight,water content and root/shoot ratio,and drastically increased the leaf electrolyte leakage.However,compared with the plant treated only with NaCl,the plant dry weight,root/shoot ratio and water contents of the seedlings treated with foliage spraying in 600 mg/L of PP333 under NaCl stress were all increased significantly,and their leaf electrolyte leakage percentage was decreased significantly.（2） The photos of transmission electron microscope indicated that the leaf cells of J.curcas contained distinct starch grains,that elliptic chloroplasts clung closely to cell wall under control and that plasmolysis phenomenon and cell membrane damage of leaf cells under 200 mmol/L NaCl were obviously visible.Moreover,NaCl-treated chloroplasts did not contain starch grains but formed osmiophilic globules.However,in J.curcas seedlings treated with salt and with foliage spraying in 600 mg/L of PP333,plasmolysis phenomenon did not occur,osmiophilic globule numbers decreased and osmiophilic globule volume diminished evidently.（3） J.curcas seedlings treated with 200 mmol/L NaCl showed weak osmotic adjustment ability（0.06 MPa） in leaves.However,the seedlings treated with foliage spraying in 600 mg/L of PP333 significantly displayed evident promotion in osmotic adjustment ability（0.49 MPa in leaves of non-NaCl treatment and 0.30 MPa in leaves of NaCl treatment）.（4） Compared with control,in salt-treated J.curcas seedlings,chlorophyll content and net photosynthetic rate（Pn） were both decreased evidently.Compared with salt treatment,in the seedlings treated with salt and spraying in 600 mg/L of PP333,the chlorophyll content and net photosynthetic rate（Pn） were both increased significantly.（5） Compared with control,in salt-treated J.curcas seedlings,MDA content and POD activity were greatly enhanced,and SOD and CAT activities were decreased significantly.However,compared with salt treatment,in seedlings treated with salt and foliage spraying in 600 mg/L of PP333,MDA content and POD activity were significantly decreased,but SOD and CAT activities increased.To sum up,promotion of salt adaptation of J.curcas with foliage spraying in PP333was mainly attributed to enhancement of the photosynthesis,the osmotic adjustment ability and the antioxidation ability.