A form of Rhizobium contained within the vesicles formed by the root cells of a root nodule.
A process in which positively charged minerals are made available to a plant when hydrogen ions in the soil displace mineral ions from the clay particles.
The alternation of planting a nonlegume one year and a legume the next year to restore concentration of fixed nitrogen in the soil.
A type of mycorrhiza in which the mycelium forms a dense sheath, or mantle, over the surface of the root. Hyphae extend from the mantle into the soil, greatly increasing the surface area for water and mineral absorption.
A type of mycorrhiza that, unlike ectomycorrhizae, does not have a dense mantle ensheathing the root. Instead, microscopic fungal hyphae extend from the root into the soil.
A plant that nourishes itself but grows on the surface of another plant for support, usually on the branches or trunks of tropical trees.
In plants, a chemical element that is required for the plant to grow from a seed and complete the life cycle, producing another generation of seeds.
(plural, haustoria) In symbiotic fungi, specialized hyphae that can penetrate the tissues of host organisms.
A distinct layer of soil, such as topsoil.
Decomposing organic material found in topsoil.
A group of flower tightly clustered together.
The most fertile of all soils, made up of roughly equal amounts of sand, silt, and clay.
A chemical substance that an organism must obtain in relatively large amounts. See also micronutrient.
An element that an organism needs in very small amounts and that functions as a component or cofactor of enzymes. See also macronutrient.
An essential chemical element absorbed from the soil in the form of inorganic ions.
Mutualistic associations of plant roots and fungi.
The assimilation of atmospheric nitrogen by certain prokaryotes into nitrogenous compounds that can be directly used by plants.
An enzyme complex, unique to certain prokaryotes, that reduces N2 to NH3.
Microorganisms that restock nitrogenous minerals in the soil by converting nitrogen to ammonia.
A swelling on the root of a legume. Nodules are composed of plant cells that contain nitrogen-fixing bacteria of the genus Rhizobium.
An emerging nondestructive technology that seeks to cheaply reclaim contaminated areas by taking advantage of the remarkable ability of some plant species to extract heavy metals and other pollutants from the soil and to concentrate them in easily harvested portions of the plant.
Long-term productive farming methods that are environmentally safe.
A mixture of particles derived from rock, living organisms, and humus.
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