Response Of Sagittaria Graminea To Cadmium Stress

Cadmium（Cd）is a widespread heavy metal pollutant that can cause harm to humans and most plants.Cd can enter the aquatic environment through natural environment or human factors,thereby affecting the growth and development of aquatic plants and animals.Phytoremediation,using plants to eliminate pollution and purify the environment,is a low-cost,good-efficiency,and green alternative technology today.Sagittaria graminea is a perennial emergent herb with long oval leaves,long petioles,white flowers,delicate and elegant,high vegetative reproduction coefficient and strong resistance.It is a very rare and excellent material for water virescence.In this paper,Sagittaria graminea was used as the test material,and different Cd concentrations(0.0,0.1,0.5,1.0,5.0,10.0 and 50.0 mg·L^-1)on the morphological and physiological characteristics of Sagittaria graminea was studied by solution culture,the absorption and transport capacity of Cd in Sagittaria graminea were analyzed.This research will provide a theoretical basis for its application in ecological remediation of cadmium-polluted water bodies.The main results were as follows:（1）With the increase of Cd concentration,the growth indicators showed a trend of increasing first and then decreasing,reaching the maximum under the treatment of 1.0 mg·L^-1,and the growth of Sagittaria graminea was the best.The growth of Sagittaria graminea was slow when the Cd concentration continued to increase(≥1.0 mg·L^-1).When the Cd concentration was 50.0 mg·L^-1,the growth index reached the minimum value,and the leaf wilting and root death occurred in Sagittaria graminea.In general,Cd treatment showed the phenomenon of"low promotion and high inhibition"on the growth of Sagittaria graminea.（2）With the increase of Cd concentration,the photosynthetic pigment content of Sagittaria graminea gradually decreased,indicating that Cd stress had an effect on the synthesis of photosynthetic pigments in Sagittaria graminea,thereby inhibiting photosynthesis.With the increase of Cd concentration,the values of F_v/F₀ and F_v/F_m of Sagittaria graminea gradually decreased,indicating that Cd stress damaged the potential active center of PSⅡ.With the increase of Cd concentration,the cell membrane permeability of the leaves of Sagittaria graminea increased and the content of malondialdehyde increased,and the growth of Sagittaria graminea was affected.The content of soluble sugar and proline showed an upward trend under low-concentration Cd stress,and continued to decrease under high-concentration Cd stress,indicating that the high concentration inhibited the osmotic adjustment effect of the leaves of Sagittaria graminea.（3）Under Cd stress,Sagittaria graminea had different effects on the absorption of mineral nutrient elements.Ca,K,Cu,Zn,and P elements in the leaves showed the characteristics of"low promotion and high inhibition";Fe and Mn elements showed a rising trend;Mg elements showed a trend of first falling and then rising.The content of Fe,Cu,Mg,and Mn in the root system showed an increasing trend;the elements of K and Zn showed a downward trend;the content of Ca and P showed the characteristics of"low promotion and high inhibition".It can be seen that under the stress of Cd,Sagittaria graminea has a certain degree of influence on the absorption of mineral elements.Most of the elements in the leaves are characterized by"low promotion and high inhibition",and most of the elements in the root system show an increasing trend.（4）When the Cd concentration was 10.0 mg·L^-1,the maximum Cd enrichment coefficient in the roots of Sagittaria graminea could reach 222.94,and the Cd enrichment coefficient of the leaves could reach 63.37,indicating that Sagittaria graminea had a strong ability to accumulate Cd.It was an ideal plant for cadmium-polluted water restoration.The Cd accumulated in Sagittaria graminea mainly existed in the roots,and a small part was transported to the above ground.Holding a large amount of Cd in the roots and avoiding its toxic effects on the ground could be an important mechanism for Sagittaria graminea to tolerate Cd.