The Physiological Response Of Stachys Lanata To Cd And NaCl Stress And Subcellular Distribution Of K⁺?Na⁺?Cd²⁺

With the development of urbanization and industrialization,there is a simultaneous threat of cadmium?Cd?and salinization pollution in industrial areas,nurseries,riverway,and green space soils in cities.Finding high-quality plant resources that are both salt-tolerant and capable of accumulating Cd and exploring the mechanism of salt stress on Cd uptake by plants could provide theoretical basis and practical basis for the restoration and reconstruction of vegetation in salt and Cd combined pollution areas.So we selected stachys lanata,a kind of perennial herb with certain salt tolerance and anti-heavy metal potential,with pot experiment,four single and combined treatments of gradient NaCl?0,0.1%,0.2%,0.3%?and different concentrations of Cd²⁺(0,10,30,50 mg·kg^-1),main osmoregulatory substances,antioxidant enzyme activities,photosynthetic physiology,and effects of K⁺,Na⁺,Cd²⁺uptake,translocation,and subcellular distribution were systematically studied.The results of the experiment are listed as follows:?1?0.1%NaCl and 10 mg/kg Cd²⁺stress had certain beneficial effects on dry weight,plant height,root surface area,root volume,and root mean diameter of the stachys lanata seedlings,but 0.3%NaCl and 50 mg/kg Cd²⁺complex treatment had a significant inhibitory effect on the growth,and NaCl and Cd²⁺have a synergistic effect on root damage.?2?Single and combined treatment of NaCl and Cd²⁺increased MDA content and relative conductivity;0.2%NaCl and?30 mg/kg Cd²⁺treatment increased soluble sugar,soluble protein and proline content,and increased SOD,POD and CAT activities,indicating that stachys lanata maintains osmotic balance and balance of active oxygen metabolism by increasing the content of major osmotic regulators and increasing the three major antioxidant enzyme activities.?3?Under NaCl stress,P_n?G_s?C_i and T_r of stachys lanata seedlings decreased gradually,and stomatal limitation was the main reason for the decline of photosynthetic rate;Fv/Fm,Fv'/Fm',?_PSII,ETR and qP decreased with the increase of NaCl concentration.?p<0.05?,indicating that the NaCl stress destroyed the PSII complex structure,the photosynthetic electron transport rate decreases,and the light energy conversion is hindered.Under the Cd²⁺stress,chlorophyll content increased,P_n and T_r increased gradually,and Cd²⁺stress increased Fv/Fm,Fv'/Fm',?_PSII,qP and ETR at first and then decreased.The above parameters at 30 mg/kg Cd²⁺had maximum values.It shows that the stachys lanata has some photosynthetic adaptability to Cd²⁺.Under the combined treatments of 0.3%NaCl and 50 mg/kg Cd²⁺,the chlorophyll fluorescence parameters except NPQ were lower than CK and lower than that of single NaCl and Cd treatments,indicating that NaCl and Cd had synergistic toxic effects on PSII of stachys lanata seedlings,and the NaCl is the main toxicant.?4?The K⁺,Na⁺and Cd²⁺absorbed by the stachys lanata were mainly accumulated in the roots;under the conditions of NaCl stress,the contents of K⁺,Na⁺,and Cd²⁺increased,indicating that NaCl promoted the stachys lanata absorbing of K⁺,Na⁺,and Cd²⁺;The distribution order of K⁺and Na⁺sub-cells in seedling leaves and roots was F3>F1>>F2;the distribution order of Cd²⁺in leaves was F3>F1>F2,and roots was F1>F3>F2,indicating that K⁺,Na⁺,Cd²⁺absorbed by stachys lanata mainly accumulate in cell wall and soluble components.In summary,it is considered that stachys lanata has ability of salt tolerance and Cd resistance.In the soil,the combined pollution areas with NaCl?0.2%and Cd²⁺?30mg/kg can grow normally and keep large biomass,which can be used as greening herbs applied in Cd-contaminated saline soil areas.