Hordeum jubatum L. is a perennial herb with high ornamental value and strong stress tolerance. Nitrogen deposition and cold stress are key environmental factors that affect stability of ecosystems in cold regions of northeast China. These factors significantly affect plant growth and development. Arbuscular mycorrhizal fungi (AMF) are symbiotic soil fungi that can increase plant resistance and growth. However, research on impacts of nitrogen deposition and cold stress on roots of H. jubatum-AM symbionts remains limited. Root biomass (dry and fresh weight), architecture (length, surface area, volume, forks, number of fourth-order roots, and root fractal dimension), and ultrastructure of H. jubatum were assessed, both in the presence and absence of AMF, under conditions of nitrogen deposition and cold stress. Cold stress inhibited all indicators of root architecture and disrupted root ultrastructure, with greater inhibition shown in the N2 (NH4+/NO3- = 1:1) treatment under cold stress, indicating nitrogen deposition increased sensitivity of H. jubatum to cold stress. Inoculation with AMF significantly reduced damage caused by nitrogen deposition and cold stress on H. jubatum roots compared with the non-inoculation treatment. Our results demonstrate different effects of the interaction of nitrogen deposition and cold stress versus single stress (nitrogen deposition or cold stress) on plant root development and provide a scientific basis for the use of mycorrhizal technology to improve resistance and productivity of cold-tolerant plants in cold regions under stress conditions.

Iron (Fe) is an essential trace element for plant growth, but its availability in saline soils is limited. Salt stress aggravates Fe-deficiency stress in plants. We report the effects of adding sodium nitroprusside (SNP) on peanut seedlings in saline and Fe-deficient environments. Seedlings were grown hydroponically. Seedling growth was compared after adding SNP to nutrient solutions: salt (100 mM NaCl), Fe (0 mu mol L- 1 EDTA-Fe), and combined Fe + salt (Fe + 100 mM NaCl). Combined salt and Fe-deficiency yellowed peanut leaves, caused severe oxidative stress, and inhibited seedling growth. Addition of SNP alleviated this damage, with each seedling height, fresh dry weight, and root viability increasing. Adding SNP promoted reduction in Fe3+, the transport of Fe from underground to aboveground seedling parts, and from the cell wall to organelles and soluble parts. SNP increased contents of active Fe and chlorophyll in leaves, alleviated new-leaf yellowing, increased antioxidant enzyme activities and osmotic regulator contents, and removed excess reactive oxygen species, and MDA content and electrolyte extravasation rates in leaves and roots, thereby maintaining membrane structure stability. SNP promoted absorption of K, Ca, and Mg and their transport to shoots, increased Fe availability, and improved the ion imbalance and toxicity caused by salt and Fe stress. Salt stress worsened Fe deficiency stress in peanut, but adding SNP alleviated this. SNP promoted the reduction and transport of Fe in peanut, and increased Fe availability, improving the reduction and absorption of Fe in the environmental medium by roots.