Effects Of Salt Stress On Coreopsis Tinctoria Seed Germination And Its Seedling Physiological And Growth Characteristics

Kunlun chrysanthemum,Coreopsis tinctoria Nutt., is also named two color coreopsis, which is native to the Midwest part of the United States and are grown widely at Kunlun mountains in Xinjiang’s Hotan prefecture with the altitude of 3000 m. The flower of Coreopsis tinctoria is rich in active compounds which can lower human blood pressure, reduce blood fat and help with tumor therapy and anti-ageing, therefore it is very popular in Uygur conventional medicine. The yield of wild Kunlun chrysanthemum is very limited because of its strict environmental requirements. Hence, improving the cultivated Coreopsis tinctoria yield is one of the most important practices to meet consumers’ demands. In this experiment, seeds and seedlings of Coreopsis tinctoria were treated with different concentrations of Na Cl, Na2SO4 and Mixed salts(Na Cl:Na2SO4:Na2CO3=2:7:1) to evaluate the effects of salt stress on seeds germination and plant growth. This experiment will provide growers theoretical basis and technical guidance for Coreopsis tinctoria cultivation in a larger and larger area. The results of this study are as follows:1. The seed shape of Coreopsis tinctoria is spindle, with 2.45±0.03 mm long and 0.85±0.01 mm wide. The seed skin is brown or dark brown and the average weight of 1000 seeds is 0.3893±0.0024 g. The most suitable condition of Coreopsis tinctoria seed germination is 4h soaking with an environmental temperature of 20-25℃. Seeds can normally germinate in either light or dark conditions.2. Salt stress make Coreopsis tinctoria seeds have a decreased trend significantly in germination index, germination trend and germination rate, the inhibition strengthened with the increase of salt density, different types and density of three kinds of salts have a order in inhibition strength for snow daisy seed germination as follow, Mixed salt>Na Cl>Na2SO4. The suitable salt-resistant range for Coreopsis tinctoria seeds as folllow: Na Cl 0.78%,Na2SO4 0.84%,Mixed salt at 0.15%; density of salt-resistant semilethal is:Na Cl 1.34%, Na2SO4 1.41%, Mixed salt at 0.89%.the limit density of salt-resistant is: Na Cl 2.23%,Na2SO4 2.31%, Mixed salt at 2.08%.3. With the increase of stress concentrations,net photosynthetic rate(Pn), stomatal conductance(Gs) and transpiration rate(Tr) of Coreopsis tinctoria seedlings all dropped. However, lower concentrations of Na Cl and Na2SO4 and Mixed saltss stress(50,100 mmol/L) decreased the leaf intercellular CO2 concentration(Ci) and the situation was opposite with higher concentrations. The chlorophyll content of Coreopsis tinctoria leaves with lower concentrations of Na Cl and Na2SO4 and Mixed salts stress(50, 100 mmol/L) showed a slight drop in, but there was no significant difference in comparison with that of the control; higher concentrations of Na Cl, Na2SO4 and Mixed salts stress(150, 300 mmol/L) signif icantly decreased chlorophyll content.4. With the increase of Na Cl, Na2SO4 and Mixed salts concentrations, the contents of soluble sugar, soluble protein, proline(Pro) and malondialdehyde(MDA) in the seedling leaves increased too while the enzyme activities of superoxide dismutase(SOD) and peroxidase(POD) first went up and then went down.5. The plant height, root length, dry weight and fresh weight of the root as well as aboveground parts were all decreased by salt stress, and with the increase of the salt concentrations, the values of the parameters above were all gradually declined. All parameters showed significant ly differences with 300 mmol/L salt stress, in which treatment the seedling height and root length with Na Cl, Na2SO4 and processing Mixed reduced by 16.39%, 55.06%, 63.12% and 16.39%, 55.83%, 72.43% respectively compared to those of control.