不同钙浓度对两种岩溶植物幼苗生长及其酶活性的影响

该研究采用砂培法,以狗骨木(Swida wilsoniana)和南酸枣(Choerospondias axillaris)两种岩溶植物为研究对象,用不同钙离子(Ca~(2+))浓度(设为5、35、70、150、300 mmol·L~(-1)的5个水平)的营养液进行培养,研究其对两种植物的生长及酶活性的影响。结果表明:狗骨木和南酸枣的株高在5 mmol·L~(-1)时最大,之后随Ca~(2+)浓度上升呈下降趋势,南酸枣在300 mmol·L~(-1)时有所回升。两种植物的根、枝、叶生物量和总生物量随着Ca~(2+)浓度增加而减少。狗骨木叶、枝、根的生物量分配比率为根枝叶,南酸枣在35 mmol·L~(-1)时表现为根枝叶,其他在Ca~(2+)浓度下均为枝根叶,叶生物量分配少。狗骨木和南酸枣的丙二醛(MDA)含量在150 mmol·L~(-1)时最低,且狗骨木的低于南酸枣。钙胁迫下,与南酸枣相比,狗骨木维持较高的过氧化氢酶(CAT)活性和可溶性糖含量。两种植物在5和150 mmol·L~(-1)的Ca~(2+)浓度下各项指标处于较适水平,而在300 mmol·L~(-1)的高钙离子浓度下受到明显的胁迫,对比两种植物,狗骨木较南酸枣在高钙浓度下有更好的适应性。

Effects of different calcium concentrations on seedling growth and enzyme activities of two karst plant species

Calcium(Ca)is an essential nutrient for plant growth; however, high Ca concentrations have detrimental effects on several plant species, while a few plant species have adapted to high levels of Ca via multiple mechanisms. The limestone soils of karst regions in southwest China are characterized by high levels of Ca, which have substantial influences on plant physiological characteristics and distribution. High Ca concentrations influence photosynthesis and might even destroy organelles resulting in death of the plant. Adaptation mechanisms of plants to high concentrations of Ca are very complex processes and are relative to all aspects of plant growth. Selection of suitable tree species plays a key role in ecological restoration. In order to investigate the physiological adaptation mechanisms of plants to high calcium conditions in the karst region of Southwest China, a pot experiment was conducted with seedlings of two species, i.e., Swida wilsoniana and Choerospondias axillaris. To exclude the influences from other confounding factors, each pot was filled with sand instead of soil. The seedlings were treated with five Ca levels, i.e., 5, 35, 70, 150, 300 mmol·L^-1. The growth and enzyme activities of the two plant species were measured. The results showed that the both species were the highest at 5 mmol·L^-1, and tended to decrease with the increase in Ca concentration. The biomass of roots, branches, leaf and total biomass of both species demonstrated a downward trend as Ca concentration increase, but those of C. axillaris showed a tendency to increase for the 300 mmol·L^-1 treatment. The biomass allocation ratio was in the order of root > branch > leaf for Swida wilsoniana, and root > branch > leaf for S. wilsoniana at 35 mmol·L^-1. The biomass allocation at other Ca levels showed a variation pattern of branch > root > leaf for both species. MDA content was the greatest at 150 mmol·L^-1 for both species. MDA content of Choeropondias axillaris was lower than that of Swida wilsoniana. The soluble sugar content and CAT activity of S. wilsoniana under calcium stress were higher than those of Choerospondis axillaris. The physiological indices reached optimum levels at the Ca concentrations of 5 and 150 mmol·L^-1 for both species, while were inhibited at the concentration 300 mmol·L^-1, which led to a decline of photosynthetic capacity. Our results also revealed that S. wilsoniana had better adaptability to high Ca concentrations relative to C. axillaris.