Chapter 37 Flashcards
A soil bacterium whose population size is much enhanced in the rhizosphere, the soil region close to a plant’s roots.
rhizobacterium
An essential element that an organism needs in very small amounts. See also macronutrient.
micronutrient
Association of a fungus with a plant root system in which the fungus causes the invagination of the host (plant) cells’ plasma membranes.
arbuscular mycorrhiza
A soil layer with physical characteristics that differ from those of the layers above or beneath.
soil horizon
An emerging technology that seeks to reclaim contaminated areas by taking advantage of some plant species’ ability to extract heavy metals and other pollutants from the soil and to concentrate them in easily harvested portions of the plant.
phytoremediation
The conversion of atmospheric nitrogen (N2) to ammonia (NH3). Biological nitrogen fixation is carried out by certain prokaryotes, some of which have mutualistic relationships with plants.
nitrogen fixation
A plant that nourishes itself but grows on the surface of another plant for support, usually on the branches or trunks of trees.
epiphyte
Long-term productive farming methods that are environmentally safe.
sustainable agriculture
A plowing technique that minimally disturbs the soil, thereby reducing soil loss.
no-till agriculture
The practice of growing different crops in succession on the same land chiefly to preserve the productive capacity of the soil.
crop rotation
A swelling on the root of a legume. Nodules are composed of plant cells that contain nitrogen-fixing bacteria of the genus Rhizobium.
nodule
A form of the bacterium Rhizobium contained within the vesicles formed by the root cells of a root nodule.
bacteroid
A symbiotic fungus whose hyphae grow through the cell wall of plant roots and extend into the root cell (enclosed in tubes formed by invagination of the root cell plasma membrane).
arbuscular mycorrhizal fungus
An essential element that an organism must obtain in relatively large amounts. See also micronutrient.
macronutrients
The soil region close to plant roots and characterized by a high level of microbiological activity.
rhizosphere
The natural process by which nitrogen, either from the atmosphere or from decomposed organic material, is converted by soil bacteria to compounds assimilated by plants. This incorporated nitrogen is then taken in by other organisms and subsequently released, acted on by bacteria, and made available again to the nonliving environment.
nitrogen cycle
A harmless fungus, or occasionally another organism, that lives between cells of a plant part or multicellular alga.
endophyte
A mutualistic association of plant roots and fungus.
mycorrhiza
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.
cation exchange
A method in which plants are grown in mineral solutions rather than in soil.
hydroponic culture
The most fertile soil type, made up of roughly equal amounts of sand, silt, and clay.
loam
A mixture of particles derived from rock, living organisms, and decaying organic material (humus).
topsoil
Decomposing organic material that is a component of topsoil.
humus
(1) The union of haploid gametes to produce a diploid zygote. (2) The addition of mineral nutrients to the soil.
fertilization
Association of a fungus with a plant root system in which the fungus surrounds the roots but does not cause invagination of the host (plant) cell’s plasma membrane.
ectomycorrhiza
