Introduction to Plants

Autotroph: Organisms which use the sun's energy to produce their own food.

Heterotroph: Organisms which consume other organisms in order to obtain energy.

A diagram for defining an Autotroph and Heterotroph:

Producer: Organisms which produce energy-rich organic molecules using light energy, and therefore are called producer.

Consumer: Organisms which eat organic material and digest it internally.

Decomposer: Micro organisms such as bacteria and fungi which receive their energy by releasing enzymes into dead plant and animal material. When the organic material is partially broken down the decomposers absorb the smaller organic compounds.

Plant detritus: Dead organic fragments such as dead leaves, twigs, and algae.

Animal detritus: Fragments of dead animals and excreta from animals.

Excreta: Organic material which has been eaten but cannot be used by the eater, and hence is excreted.

Photosynthesis: The process by which green plants or autotrophs capture Light Energy, Carbon Dioxide, and Water to feed themselves and create the by product of Oxygen, and Glucose which the plant uses as food.

Chlorophyll: A green pigment in the plant which plays a role in trapping light energy.

Soil: Organic and inorganic materials; biotic and abiotic. The average soil is made up of 25% air, 25% water, 45% mineral, 5% organic. Soil is formed slowly as rock (the parent material) erodes into tiny pieces near the Earth's surface. Organic matter decays and mixes with inorganic material (rock particles, minerals and water) to form soil. There are many different types of soils, and each one has unique characteristics, like color, texture, structure, and mineral content. The depth of the soil also varies. The kind of soil in an area helps determines what type of plants can grow. There are 12 orders (types) of soil: Alfisols, Aridisols, Entisols, Histosols, Inceptisols, Mollisols, Oxisols, Spodosols, Ultisols, Gelisols, Andisols, and Vertisols.

Physical weathering: Physical breakdown occurs when natural agencies such as wind, water, ice, and temperature change split rocks into smaller fragments.

Chemical weathering: The chemical interactions with minerals within a rock in which the rock is broken down into smaller fragments.

Inorganic components: Rock fragments, minerals; fragments such as gravel, coarse sand, fine sand, silt, and clay.

Organic components: The non-living organic matter in the soil is accumulation of dead, but intact, plant and animal tissue together with partially decomposed tissue. The organic matter within the soil is a result of the soil temperature. Cooler climates tend to have more organic soil. The desert for example, has about 1% organic matter by dry weight. Peat soils have close to 100% organic content by dry weight.

Horizon: Soil horizons are distinct layers of soil that form naturally in undisturbed soil over time. The types of horizons are indicative of the soil order. Like other natural processes, the age of the horizon increases with depth.

O Horizon: The top, organic layer of soil, made up mostly of leaf litter and humus (decomposed organic matter).

A Horizon: The layer called topsoil; it is found below the O horizon and above the E horizon. Seeds germinate and plant roots grow in this dark-colored layer. It is made up of humus (decomposed organic matter) mixed with mineral particles.

E Horizon: This eluviation (leaching) layer is light in color; this layer is beneath the A Horizon and above the B Horizon. It is made up mostly of sand and silt, having lost most of its minerals and clay as water drips through the soil (in the process of eluviation).

B Horizon: Also called the subsoil - this layer is beneath the E Horizon and above the C Horizon. It contains clay and mineral deposits (like iron, aluminum oxides, and calcium carbonate) that it receives from layers above it when mineralized water drips from the soil above.

C Horizon: Also called regolith: the layer beneath the B Horizon and above the R Horizon. It consists of slightly broken-up bedrock. Plant roots do not penetrate into this layer; very little organic material is found in this layer. R Horizon: The unweathered rock (bedrock) layer that is beneath all the other layers.

Field Capacity: Refers to the amount of water left behind in soil after gravity drains saturated soil.

Soil solution: The spaces between the particles of soil, the pore spaces can be occupied by either water or air. The proportions of water and air are interrelated; as one increases the other decreases.

Percolation: The movement of water going downward.

Capillarity: The movement of water going upward.

Leaching: To remove soluble or other constituents from by the action of a percolating liquid.

Zonal soils: Soils that develop under conditions of good soil drainage and are the most widespread of soil types.

Intrazonal soils: Soils formed under conditions of very poor drainage. Examples of these soils are Tundra, Meadow, Bog, and Saline soils.

Azonal soils: Soils which cannot be easily classified, either because they are very young, or because they are unable to develop a soil profile. Examples of these soils are Mountain, Marine, Volcanic, Glacial and Sand dune soils.

Water cycle:

Carbon cycle:

Nitrogen cycle:

Various terminolgy information gathered from the internet.