Antioxidant Enzymes And Tolerance Of Chinese V Itis To Salinity

SOIL salinity is a worldwide agricultural problem. It influences plant growth and development severely, then crop productivity. Thus investigation in salt tolerant plant germplasms is very important. In the present paper, detached branches of Vitis vinifera L. and leaf discs of 25 Chinese wild grape types of 13 species, V. riparia Michaux, Varieties from V. vinifera, and V. vinifera × V. labrusca were incubated in media with or without NaCl, plant growth regulator, or active oxygen. Changes of grape leaves in cell membrane permeability, contents of photosynthetic pigments, soluble protein, free proline , total soluble sugar and MDA , photosynthetic and respiratory CO₂ exchange, and activities of antioxi-dant enzymes (e.g. catlase, ascorbate peroxidase, guaiacol peroxidase, and superoxide dis-mutase). protein hydrolase, and malate — or glutamate — dependent NAD⁺ reductrion were measured. A cationic peroxidase was purified from V. riparia , V. bryuonifolia , and V. pseu-d oreticulata respectively. Their characteristics were compared. The data showed as follows.1. Cell membrane permeability of grape leaves was increased following the increase of NaCl concentration.2. The enhancement of permeability of grape leaf cell membrane was related to active oxygen resulting damage.3. The damage of leaf cell membrane and reduction of contents of leaf photosy thetic pigments was more severe under illumination than that in dark.4. Salt resulting decrease in pigment content was related to active oxygen.5. Superoxide dismutase of V. riparia leaf discs was promoted by ABA, GA₃,and 6BA, but elliminated by salinity. Activities of catalase, ascorbate peroxidase, and guaiacol peroxidase of leaf discs were promoted by zeatin. A cationic peroxidase was induced by 6BA as well. thus the salt tolerance of leaf discs was improved by cytokinin. But GA₃ and ABA promoted malate—or glutamate —dependent NAD⁺ reduction, thus enhanced salt damage.6. Catalase of V. riparia leaf discs was promoted by exogenous active oxygen, but ascorbate peroxidase, guaiacol peroxidase, and superoxide dismutase were inhibited.7. The tested Chinese Vitis could be devided into 4 groups:1)salt tolerant group, including Vitis bryonifolia (Anlin — 2 and Anlin—3), V. amurensis (Shuangyou) , V . romanetii (Liuba—1 and Jiangxi—1), V.adstricta, V.davidii (Xuefeng), V.davidii var cyahocarpa (Gang) (Langao — 5), and V. bashanica (Baihe — 42); 2) the moderately salt tolerant group, including V. amurensis (Tonghua — 3, and Zuoshan — 1), V. p seud oreticulata(Guangxi—1), V. yenshanensis, and V.bashanica (Baihe—41) ;3) the moderately salt sensitive group, including V. amurensis (Huaxian — 47), V.davidii (Jinan—1), V. psendareticu-lata (Shangnan—1), V. davidii var cyanocarpa(Gang) (Zhenan—3), and V. baihensis-,4) salt sensitive group, including V. piasezkii (Gansu — 91) , V. davidii (Tangwei) , and V. qm-lingensis (Pingli—5 and Lueyang—4). The most tolerant grape could maintain a high level of antioxidant enzymes under salinity. NaCl promoted the expression of cationic peroxidase, CAT 1, and CAT 2 of leaves of salt tolerant grape.8. Salt tolerant group could also maintain a Chi a/Chl b or Chl/carotenoids ratio under salinity, but salinity enhanced these ratios of salt sensitive grape.9. All cationic peroxidase from V. raparia , V. bryonifolia or V. psend oreticulata had a maxium absorption at 450nm, their optium pH value was 5. 23, 6. 14—6. 47, and 5. 76 respectively when guaiacol was used as substrate, their apparent Vmaxand Km were 105,4016, and 637umol/min/mg protein, and 1. 10, 3. 17, and 1. 02 mmol/L H2O2 respectively. The molecalar weight of cationic peroxidase from V. pseudoreticulata was about 39KD.10. The cationic peroxidase was promoted by salt, which following the order :Ca2+> K+>Na+,Zn2+>Mn2+>Mg2+, and Cr>NO3-,SO2->PO^.The mechanism of grape salt tolerance was discussed.