Chapter 37: Soil and Plant Nutrition

Comprehensive vocabulary flashcards covering the biological and chemical aspects of soil composition, nutrient cycles, and specialized plant adaptations as presented in the lecture notes.

Humus

Decomposing organic material that prevents packing of smaller mineral particles and allows retention of water.

Soil Texture

The classification of soil particles by size, categorized as sand (largest), silt, and clay (smallest).

A Horizon

Also known as topsoil, this soil horizon is a mix of humus and minerals.

Loams

Soils that contain equal amounts of sand, silt, and clay, often considered some of the best soils for growth.

Cation Exchange

A process where plants decrease the soil fluid pH so that $H^+$ ions are exchanged for mineral cations bound to negatively charged soil particles.

Leaching

The removal of nutrients from soil by water that percolates through it, which is most pronounced in sandy soils.

Aquifers

Underground water reserves that serve as a primary source for irrigation but can become depleted.

Essential Element

A chemical element required by a plant to complete its life cycle.

Macronutrients

Elements required by plants in relatively large amounts, including $carbon$, $oxygen$, $hydrogen$, $nitrogen$, $phosphorus$, $sulfur$, $potassium$, $calcium$, and $magnesium$.

Micronutrients

Elements needed in only small amounts that function mainly as cofactors in enzymatic reactions, such as $chlorine$, $iron$, $manganese$, $boron$, $zinc$, $copper$, $nickel$, and $molybdenum$.

Limiting Nutrient

A nutrient whose relative availability in the environment is less than a plant’s requirement for it.

Nitrogen Fixation

The process by which bacteria convert atmospheric $N_2$ into ammonia ($NH_3$).

Ammonification

The conversion of nitrogen-containing organic material into ammonium ($NH_4^+$) by bacteria.

Nitrification

The bacterial process of converting ammonium ($NH_4^+$) into nitrate ($NO_3^-$).

Denitrification

The process where bacteria convert nitrate ($NO_3^-$) back into atmospheric nitrogen ($N_2$).

Rhizobium

Bacteria that form a symbiotic relationship with legumes, living in root nodules and converting $N_2$ into ammonium ($NH_4^+$).

Leghemoglobin

An iron-bearing protein that helps provide a low-$O_2$ environment for the nitrogen-fixation process inside root nodules.

Mycorrhizae

A mutualistic relationship between soil fungi and plant roots where the fungus receives sugar and the plant receives additional water and nutrients.

Ectomycorrhizae

Fungi where the mycelium forms a dense sheath or mantle over the root surface and grows into the root cortex apoplast without penetrating the cells.

Endomycorrhizae

Also called arbuscular mycorrhizae, these fungi have hyphae that penetrate the root epidermal cells and form branched structures called arbuscles within the cortex cells.

Epiphytes

Plants that grow on other plants or hard surfaces rather than being rooted in soil, absorbing water and minerals mainly from rain through their leaves.

Parasitic Plants

Plants that live on other plants and draw resources from their host; examples include Mistletoe, Dodder, and Indian Pipe.

Carnivorous Plants

Photosynthetic plants that obtain nitrogen and essential minerals by ingesting insects, typically found in acidic bogs.