关键词: Iris lactea; nitrate nitrogen; plant nutrient; lead accumulation; absorb; transport;
摘要：Since Pb is a non-biodegradable inorganic pollutant and a non-essential metal, its long-term presence in soil poses a great threat to the environment. Iris lactea Pall. var. chinensis (Fisch.) Koidz., a perennial dense bush herb with high resistance of Pb and wide adaptability, was used in pot experiments to study the effects of exogenous nitrate N (NO–3-N) on the absorption and transportation of Pb and plant growth under different Pb concentrations. Then, the mechanism of NO–3-N affecting Pb and nutrient uptake and transport was explored. The concentration of Pb in the experiment ranged from 0 to 1600 mg/kg, and the added concentration of NO–3-N was 0.0–0.3 g/kg. The results showed that I. lactea was highly tolerant to Pb, and the shoot fraction was more sensitive to varied Pb concentrations in the soil than the root fraction. This protective function became more pronounced under the condition of raised Pb concentration in the soil. When the concentration of Pb in the soil reached 800 mg/kg, the highest Pb content of I. lactea was found under the condition of 0.1 g/kg of NO–3-N addition. When Pb concentration in the soil increased to 1600 mg/kg, the increase in NO–3-N addition promoted Pb uptake by the root. To ensure the well growth of I. lactea and the effect of remediation of Pb-contaminated soil, the recommended concentration of NO–3-N in the soil is 0.1 g/kg. This result provides a theoretical basis for exogenous N regulation of phytoremediation of Pb-contaminated soil.
关键词: growth-promoting bacteria; physiological traits; drought stress; biofertilizer; root traits; Halimodendron Halodendron (Pall.) Voss;
摘要：Growth-promoting bacteria (GPB) have shown promising effects on serving plants against environmental constraints such as drought. Nevertheless, simultaneous effects of different GPB have less been considered for arid land plants and under field conditions. We investigated the effects of single and combined application of GPB, including free-living nitrogen-fixing bacteria (NFB), phosphate solubilizing bacteria (PSB), potassium solubilizing bacteria (KSB), a combination of NFB, PSB, and KSB (NPK), and control, at three drought stress treatments. In order to better understand the interactions between drought and GPB, we measured the morphological, biochemical, and physiological plant traits. The target plant was salt tree (Halimodendron Halodendron (Pall.) Voss), a legume shrub native to arid lands of Central and West Asia. All biofertilizer treatments enhanced the growth, physiology, and biochemistry of salt tree seedlings, and there were significant differences among the treatments. KSB and PSB treatments increased photosynthetic pigments, but KSB treatment was more efficient in transpiration rate and stomatal regulation and increased the soluble carbohydrates. PSB treatment had the highest effect on root traits, such as taproot length, root volume, cumulative root length, and the ratio of root to shoot. NFB treatment enhanced root diameter and induced biomass translocation between root systems. However, only the application of mixed biofertilizer (i.e., NPK treatment) was the most significant treatment to improve all plant morphological and physiological characteristics of salt tree under drought stress. Therefore, our results provided improvement of some specific plant traits simultaneous with application of three biofertilizers to increase growth and establishment of salt tree seedlings in the degraded arid lands.