Effect Of Salinity On Seed Germination And Seedling Growth Of Hemp

Land salinization, an important factor that hinder plant production, has become a worldwide environmental trouble and is worsening persistently. To cope with the dilemma, the mechanism of mixed salt-alkaline stress causing damages to plant and the adaptive mechanisms of plant tolerance to the stress are critical issues to be solved urgently. Hemp (Cannabis sativa L.) is an important crop with strong resistance to adverse environments that can be planted on hillside lands, even on salt soils.In this study, we used ’Yunma No.5’ and ’Bamahuoma’ as tested materials which were treated with single salt and mixed salt-alkaline under different culture conditions, and measured the indexes of germination and seedling stage. Through the treatment of different salt and different concentration of hemp, we screened the physiological and biochemical indexes closely related to salt tolerance in order to build salt resistance comprehensive evaluation method of hemp. The results showed that:1. The single salt treatment(1) The hemp seeds in germination were significantly inhibited by salt stress, and the growth of seed germination, radical, hypocotyl was significantly inhibited with the increasing concentration of salt stress, but a low concentration of salt (50mM的NaCl、 Na2SO4) was beneficial to seed germination of hemp to some extent which made the hypocotyl lengths of Yunma No.5significantly higher than the control.(2) Salt stress significantly affected the hemp seedling growth. With the increased of concentration and time of salt stress, the growth of hemp slowed down and even seemed to stop growing. Dry weight, root length, chlorophyll content, root shoot ratio and water content were significantly different from the control at the concentration of300mM, in addition, the relative electric conductivity was significantly higher than the control. SOD activities, content of Pro, MDA, soluble sugar in hemp leaves were significantly increased which showed significantly differences in different salt concentrations.(3) The results of PCA (principal component analysis) indicated that fresh weight, plant height, chlorophyll content could be used as the leading single salt resistance assessment indexes in seedling stage of hemp.2. The two kinds of salts mixed treatment(1) The hemp seeds in germination were significantly inhibited by two kinds of neutral salts mixed and two kinds of alkali salts mixed stress, all indexes were significantly decreased with the increasing salt concentration which evidently showed mixed salts were more stressed than single salts’.(2) Salt stress significantly affected the hemp seedling growth. With the increased of time of salt stress, the growth of hemp and the physiology and biochemistry indexes showed the same trend comparing to single salt treatment. Alkaline mixed salts stress was the most harmful to the hemp seedling which was evidently higher than alkaline and neutral single salt stress.(3) The results of PCA indicated that chlorophyll content, water content, and soluble sugar contant could be used as the leading two kinds of mixed salts resistance assessment indexes in seedling stage of hemp.3. The more kinds of salts mixed treatment(1) The hemp seeds in germination were significantly inhibited by more kinds of mixed salts stress at the concentration of400mM, which showed germination rate was zero.(2) Salt stress significantly affected the hemp seedling growth. The indexes of growing and physiological were significantly different to the control, and all physiological indexes were significantly higher than the control except at high pH treatment.(3) The results of PCA indicated that chlorophyll content, water content, and SOD activity could be used as the leading four kinds of mixed salts resistance assessment indexes in seedling stage of hemp.(4) There were no evident damages on hemp under different concentration of four kinds of mixed salts stress due to the antagonism.4. Treatment schemes of different salts(1) Different salt stresses has different effects on performance of hemp at the same concentration, and even the same salt stress has different effects on the growth stage, the hemp was more sensitive in germination and ’Yunma No.5’ was more salt-tolerance than’Bamahuoma’.(2) The salt-alkaline stress to the hemp growth from high to low was two kinds of mixed salt, single salt, more kinds of mixed salt, and the adaptive to neutral salt stress of hemp was stronger than alkaline salt stress. The hemp of high concentration (≥300mM) of alkaline salt stress died while normal growth under neutral salt stress.In conclusion, the hemp could adapt well to low concentration (<200mM) of salt-alkaline environment, but high concentration (≥300mM) of salt and alkali restrained greatly the growth of hemp. According to the results of pot culture, hemp is an important crop with quite strong resistance to salt-alkali that can be expected to grow in light, even in moderate salt-alkali soil, but the situations in field is more complicated, the salt-alkali resistance of the hemp still needs further study.