盐胁迫对中国柽柳幼苗生理特性的影响

Effects of salt stress on physiological characteristics of Tamarix chinensis Lour. seedlings

以中国柽柳(Tamarix chinensis Lour.)插穗为研究材料,在装有不同土壤盐分梯度(0.4%、0.8%、1.2%、1.6%、2.0%、2.4%)的盆钵中进行扦插试验,测定柽柳扦插成活率、叶绿素含量、超氧化物歧化酶(SOD)活性、过氧化物酶(POD)活性及丙二醛(MDA)含量等指标,研究分析柽柳扦插成活率及幼苗生理特性对盐分胁迫的响应特征。结果表明:(1)柽柳扦插成活率随盐胁迫增强逐渐降低,适合扦插繁殖的土壤含盐量低于0.8%;土壤含盐量超过0.8%后,扦插成活率太低,不适合柽柳进行扦插繁殖。(2)柽柳可通过提高叶绿素含量来适应盐胁迫,随着盐胁迫增强,柽柳扦插幼苗叶片中叶绿素含量先升高后降低,但过高的盐胁迫会破坏叶绿素的合成。(3)柽柳扦插幼苗叶片SOD和POD活性随盐胁迫增强先升高后降低,通过提高SOD和POD活性来清除细胞内多余的活性氧自由基,但活性氧自由基积累过多时,膜脂过氧化作用会破坏细胞膜的稳定性,导致抗氧化酶活性降低。(4)柽柳扦插幼苗叶片MDA含量随盐胁迫的增强先升高后降低。在土壤含盐量0.4%—1.2%范围内,MDA含量虽高于CK,但各盐分处理之间差异不显著。在含盐量为1.6%时,叶片细胞受到膜脂过氧化作用加强,MDA含量显著升高,但含盐量为2.0%时,MDA含量降低。

Changyi National Marine Reserve lies on the south coast of Bohai Gulf, which was established to preserve the biggest Tamarix chinensis Lour. community in China. However, human over-exploitation of the underground brine caused sea-water intrusion, whereas the annual evaporation capacity gradually increased because of the global climate changes, thereby aggravating the soil salinization and degradation. The population of T. chinensis gradually degraded under the conditions of high soil osmotic pressure, poor aeration and moisture, low nutrient availability, and high soil salinity. Therefore, the effects of salt stress on the eco-physiological characteristics of T. chinensis cuttings became very important for the ecological restoration of the coastal wetlands. In this paper, we studied the effects of different salinity （0%, 0.4%, 0.8%, 1.2%, 1.6%, 2.0%, and 2.4% NaCl solutions） on the eco-physiological characteristics of T. chinensis in the greenhouse. The survival rate, chlorophyll content, activities of superoxide dismutase （SOD） and peroxidase （POD）, and malondialdehyde （MDA） content were determined. The results showed that the survival rate of T. chinensis cuttings gradually decreased with increasing the salt stress. The survival rate was 100% in the control group. The difference of the survival rate between the control and the treatment with 0.4% NaCl was not significant, and the survival rate was about 80% in the treatment with 0.8% NaCl. The survival rate decreased significantly when the salinity increased to more than 0.8%. With the increased salt stress, the chlorophyll content initially increased and then decreased. We conclude that the seedlings were able to adapt to lower salt stress conditions by increasing the chlorophyll content, which was used to enhance the photosynthesis. However, the chlorophyll content decreased under higher salt stress conditions because the concentration of salt stress exceeded the threshold of the plant adaptation. The activities of SOD and POD increased and then decreased with the increasing salt stress conditions. The seedlings were able to eliminate the reactive oxygen species accumulated through the increasing activities of SOD and POD under lower salt stress conditions. With the salt stress increasing, the activities of SOD and POD decreased because the membrane lipid peroxidation damaged the stability of the cell membrane. MDA is an important indicator of injured cell membrane, and its content increased with increased salt stress conditions. The absence of significant difference between treatments with salt concentration less than 1.2% and significant increase in the content of MDA in the treatment with 1.6% NaCl solutions indicates that the seedlings were less influenced by the membrane lipid peroxidation when the salt stress was less than 1.2%. This phenomenon may be explained by the regulation of the antioxidant enzymes.