镍离子对尖叶莴苣氮素吸收和生长生理的影响

以‘全年油麦菜’尖叶莴苣为试验材料，采用水培方式，研究3个浓度(0 mg·L^-1、0.1 mg·L^-1、1 mg·L^-1)Ni²⁺在22.4 mg·L^-1 N处理下对尖叶莴苣氮素吸收的生长及生理影响。结果显示：(1)尖叶莴苣根系和地上部生物量随处理时间的增加呈上升趋势。与对照T₁(0 mg·L^-1 Ni²⁺、112 mg·L^-1 N)相比，T₂处理(0 mg·L^-1 Ni²⁺、22.4 mg·L^-1 N)对尖叶莴苣根系及叶片生长具有一定抑制作用，植株鲜重、干重、根冠比、根系长度、平均直径、表面积、体积、根尖数、分根数、叶片表面积和体积在T3处理(0.1 mg·L^-1 Ni²⁺、22.4 mg·L^-1 N)下显著高于对照，T₄处理(1 mg·L^-1 Ni²⁺、22.4 mg·L^-1 N)对尖叶莴苣根系及其叶片生长具有一定促进作用，但对其根尖数和分根数表现出一定抑制性。(2)随着Ni²⁺浓度的增加，尖叶莴苣叶片叶绿素a、叶绿素b和总叶绿素含量呈先升后降的变化规律，且均在T₃处理下显著提高。(3)随着处理时间的增加，尖叶莴苣叶片的净光合速率(P_n)、气孔导度(G_s)和蒸腾速率(T_r)逐渐上升，胞间CO₂浓度(C_i)逐渐下降，且T₃处理叶片的G_s显著高于对照，其C_i最低，P_n最大。(4)施加Ni²⁺对尖叶莴苣有机酸、可溶性蛋白和可溶性糖含量以及SOD和POD活性有显著影响，在T₃处理下有机酸含量降低，可溶性糖和可溶性蛋白含量显著增加，SOD和POD活性显著提高。(5)T₃处理尖叶莴苣根系中N及叶片中B和Ca含量较高；根系中Ni含量高于叶片，T₃处理叶片中的Ni含量较低，Mg含量较高；植株体内Cu含量随Ni²⁺浓度增加而下降。研究表明，外源Ni²⁺处理能影响低氮条件下(22.4 mg·L^-1 N)尖叶莴苣幼苗生长及生理状况，适宜浓度(0.1 mg·L^-1)Ni²⁺可有效提高尖叶莴苣根系对氮素的吸收利用效率，减少氮素施用量，促进尖叶莴苣根系和地上部叶片生长，增加光合色素含量，并提高净光合速率，进而改善植株的产量和营养品质。

Effect of Nickel Ion on Growth, Physiology and Nitrogen Absorption in Lactuca sativa L. Seedling

We investigated the growth and physiological effects of Ni²⁺ at 3 concentrations (0 mg·L^-1, 0.1 mg·L^-1, 1 mg·L^-1) with 22.4 mg·L^-1 N on nitrogen uptake in the seedling stage of Lactuca sativa L. using hydroponic. The results showed: (1) the root and shoot biomass of the lettuce increased with the increase of treatment time. Compared with the control T₁ (0 mg·L^-1 Ni²⁺ and 112 mg·L^-1 N), T² treatment (0 mg·L^-1 Ni²⁺ and 22.4 mg·L^-1 N) had certain inhibitory effects on the root growth and leaf growth of the lettuce; the fresh weight of the plant, dry weight, root to shoot ratio, root length, mean diameter, surface area, volume, number of root tips, number of roots, leaf surface area and volume were significantly higher under T₃ (0.1 mg·L^-1 Ni²⁺ and 22.4 mg·L^-1 N) treatment for comparison, T₄ treatment (1 mg·L^-1 Ni²⁺ and 22.4 mg·L^-1 N) promoted the growth of roots and leaves of the lettuce, but showed some inhibition on the number of root tips and roots. (2) With the increase of Ni²⁺ concentration, the contents of chlorophyll a, chlorophyll b and total chlorophyll in the leaves of the lettuce showed a first increase and then decrease, and both of them significantly increased under T₃ (0.1 mg·L^-1 Ni²⁺ and 22.4 mg·L^-1 N) treatment. (3) With the increase of treatment time, the net photosynthetic rate (P_n), stomatal conductance (G_s) and transpiration rate (T_r) of the leaf lettuce gradually increased, and the intercellular CO₂ concentration (C_i) gradually decreased. The stomatal conductance (G_s) of leaves with T₃ (0.1 mg·L^-1 Ni²⁺ and 22.4 mg·L^-1 N) treatment was significantly higher than that of the control, the intercellular CO₂ concentration (C_i) was the lowest, and the net photosynthetic rate (P_n) was the largest. (4) Applying Ni²⁺ to pointed leaf lettuce, organic acid, soluble protein, soluble sugar content, POD and SOD activities had significant effect. With T₃ (0.1 mg·L^-1 Ni²⁺ and 22.4 mg·L^-1 N) treatment, organic acid content decreased, while soluble sugar and soluble protein contents increased significantly,SOD and POD activities were significantly improved. (5) With T₃ treatment, the contents of B and Ca in roots and N in leaves were higher; the Ni content in roots was higher than that in leaves, the Ni content in leaves was lower, and the Mg content was higher; Cu content in plants decreased with the increase of Ni²⁺ concentration. Research shows that exogenous Ni²⁺ treatment can affect the growth and physiological status of rapeseed lettuce seedlings under low nitrogen conditions (22.4 mg·L^-1 N). The appropriate concentration (0.1 mg·L^-1) Ni²⁺ can effectively improve the nitrogen absorption and utilization efficiency of the root system of rapeseed lettuce, reduce the amount of nitrogen application, promote the growth of the root system and aboveground leaf of rapeseed lettuce, increase the photosynthetic pigment content, and improve the net photosynthetic rate, thus improve the yield and nutritional quality of the plant.