| Calcium is an essential nutrients for plant growth, also has important functions for plant growth. Adaptation mechanism of plants to high concentration of calcium is a very complex process, which is an integrative relative to all aspects of plant growth. Therefore, the study of plant adaptation to the environment with high calcium in karst area is of great importance for revealing the eco-physiological adaptation mechanism of plants to high calcium environment, development of community ecology, rapid vegetation restoration, and ecological reconstruction in the karst areas of Southwest China.This research was conducted in the combination with control experiment and experiment analysis, chosing two karst typical plant species, i.e., Swida wilsoniana and Choerospondias axillaris as the research object. Through analysis of the photosynthetic characteristics, enzyme activities, and nutrient elements under high calcium stress with an artificial control of Ca supply(5、35\ 70、150、300 mmol·L-1), the plant adaptation mechanism to high Ca environment in karst area was studied. The results were as follows:1. The increasing calcium concentration has inhibited the growth of Swida wilsoniana and Choerospondias axillaris, and the inhibition degree of plants increased as the increasing concentration of calcium ion. Plants grew poorly in the high concentration of calcium ions. Due to increasing calcium ion concentration increased stress on plants through blocking the upward transport of plant nutrients, and then reducing the proportion of leaf biomass of Swida wilsoniana and Choerospondias axillaris.2. Swida wilsoniana and Choerospondias axillaris had a larger diurnal variation of Pn in the calcium ion concentration of 150 mmol·L-1. The Fv/Fo, Fv/Fm, qP also reached at a high level in the 150 mmol·L-1 calcium ion, which indicated that a certain amount of calcium could improve the photosynthetic capacity of Swida wilsoniana and Choerospondias axillaris. Under the high calcium concentration, Swida wilsoniana and Choerospondias axillaris’s chlorophyl content reduced.3. With the increase in the concentration of calcium ions in the environment, the CAT, SOD, and MDA activities and soluble sugar content of Swida wilsoniana and Choerospondias axillaris have no clear rules. But it produced a toxic effect on leaf cells under the calcium concentration of 300 mmol·L-1. Due to long-term cultivation of calcium stress, plants have adapted different adaptability to calcium environment. However, the highest calcium concentration destroyed the enzyme system of plants and led to an irregular change of plant enzyme.4. Different calcium concentrations had significant impact on the absorption of nutrient elements of Swida wilsoniana and Choerospondias axillaris. Under the long-term culture of calcium, the distribution of N, P, K, Ca, and Mg in the two plant species was in the order of leaf> root> branch, and the accumulation of various elements in leave and root were significantly higher than branch. The N, P, K, Ca, and Mg reduced at different levels as the calcium concentration rising, but at the calcium concentration of 150 mmol·L-1 both Swida wilsoniana and Choerospondias axillaris absorbed more nutrients. High calcium had a significantly inhibition on mutrient uptake for Swida wilsoniana and Choerospondias axillaris, while at some level of calcium ion concentrations were good for the growth of plant.5. Various physiological indicators of Swida wilsoniana and Choerospondias axillaris was higher at the calcium concentration of 5 mmol·L-1 simulated an acid soil and 150 mmol·L-1 simulated a lime soil, which reflected the Swida wilsoniana and Choerospondias axillaris two typical Karst plants had a good adaptability in both acid soil and lime soil environment with calcium pressure. And two typical Karst plants had obvious stresses at the calcium concentration of 300 mmol·L-1, which caused an reduction of growth, nutrient absorption, and photosynthetic capacity. Comparison of the two plants, Swida wilsoniana have better adaptability than Choerospondias axillaris in high calcium concentration. |
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