Studies On Seed Germination Characteristics And Salt Tolerance Of Two Species Of Nitraria L.

Nitraria L. is an old small genus of Zygophyllaceae which is a tertiary relict. It is one of the dominant species or specie of the construction in the Mediterranean-Central Asian desert flora in the shrub layer. There are about 12 species distributed in Asia, Europe, Africa and Australia desert; In China, there are seven kinds.In inner Mongolia, there are four kinds that are N.sibirica Pall.,N.tangutorum Bobr.,N.roborowiskii Kom.,N.sphaerocarpa Maxim..The genus is the one of important constructive species in inner Mongolia,Gansu and Xinjiang desert vegetation.It is the fine sand-fixing pioneer plant that for the resistance to drought,salinity,resistance to wind erosion of sand burial,fast growth and easy propagation.This genus is highly adapt to the saline desert environment, which can growth well in the soil with 3% salt content of the areas.The plant can be used to improve saline-alkali soil and improve soil fertility. In recent years, with the serious deterioration of the natural environment and human being's deeply damage, Nitraria L. is a major construction group in varying degrees of degradation,large area of death or poor growth, and spikelet fertility or firmness, this particular breeding population of wild resources is facing serious threats. So the study of the artificial propagation of Nitraria L. has great significance. In this thesis, we will study the N.tangutorum Bobr. and N.roborowiskii Kom. that are more widely distributed in Inner Mongolia. Through studying the seed breeding and tissue culture, we discuss the method of improving plant breeding capacity. Under the salt stress, we can measure the changes in antioxidant system of the salt tolerance of their seedlings in order to provide a theoretical basis for better development and use of plant resources of these salt plants. The results are as follows:1. Low vigor,water requirements of seed germination is lower than normal seeds and thick skin are the limit factors in seed germination, These situations can greatly improve after store in low temperature with sand and sulfuric acid treatment.2.60% H2SO4 treated 4h or 400mg/L GA3 treatment of two kinds of Nitraria L. are two methods to improve seed germination.3. N.tangutorum Bobr. seed germination optimum temperature is 30℃, suitable water is 3ml, seed germination in the filter bed,soil and vermiculite beds are good. N.roborowiskii Kom. seed germination optimum temperature is 25℃, suitable water is 2ml or 3ml, seed germination is good in the filter bed.4. N.tangutorum Bobr. of the best start, proliferation and rooting medium were MS+IBA 0.8mg/L,6-BA 1.5mg/L+NAA 0.2mg/L, MS+IBA 0.5mg/L; V.roborowskii Kom. of the best start, proliferation and rooting media were MS+IBA 0.5mg/L,6-BA 1.0mg/L+NAA 0.2mg/L, MS+IBA 0.5mg/L.5. N.tangutorum Bobr. and V.roborowskii Kom. with NaCl was conducted and its result demonstrated:Medium with 200mmol/LNaCl is the suitable environment of plantlets,plant height was increased 1.31cm(P<0.05), compared with the control,root length was increased 5.35cm (P<0.05); 300mmol/L NaCl seriously inhibit the growth of plantlets,50mmol/L NaCl and 100mmol/L NaCl have no significant role in growth.6. Physiological tolerance test showed that:Under the salt stress, two kinds of Nitraria L. have different adopted strategy in the antioxidant system. N. tangutorum antioxidant enzymes of SOD, POD activity increased, and the control of various NaCl concentrations were significantly different (P<0.05).At the high salt concentration (200mmol/L and 300mmol/L),APx and GR activity significantly increased (P<0.05).When the NaCl concentration≥100mmol/L, As A content was significantly increased (P<0.01), GSH content significantly increased until the NaCl concentration of 300mmol/L (P<0.05).At the high salt concentration, MDA,soluble protein and Pro content significantly increased (P<0.05). N.roborowiskii Kom. leaves of SOD, CAT activity decreased not significantly (P>0.05), POD activity significantly decreased under high salt concentration, GR activity was significantly decreased at the NaCl concentration of 300mmol/L (P<0.01), APx and antioxidants of AsA and GSH activity significantly increased at high salt concentrations (P<0.05) but changed little at low salt concentrations (NaCl concentration<100mmol/L). In N.tangutorum, antioxidant enzymes and antioxidant are work together, but in N.roborowiskii Kom. antioxidants play a major role,so that ROS generation and inactivation in a dynamic equilibrium to adapt the saline environment.