Chapter 37: Soil & Plant Nutrition

Question 1

Humus

Answer 1

Decomposing organic material that is a component of topsoil

Question 2

Topsoil

Answer 2

A mixture of particles derived from rock, living organisms, and decaying organic material

Question 3

Soil Horizon

Answer 3

A soil layer with physical characteristics that differ from those of the layers above or beneath

Question 4

Loams

Answer 4

The most fertile soil type, made of roughly equal amounts of sand, silt, and clay

Question 5

Cation Exchange

Answer 5

A process in which positively charged minarls are made available to a plant when hydrogen ions in the soil displace mineral ions from the clay particels

The more clay and organic matter in the soil, the higher the cation exchange capacity

Question 6

Essential elements

Answer 6

An element required for a plant to complete its life cycle and reproduce

Question 7

Hydroponic Culture

Answer 7

A method in which plants are grown in mineral solutions rather than soil

Question 8

Macronutrients

Answer 8

Elements that are required in relatively large amounts

• carbon, oxygen, hydrogen, nitrogen, and other major ingredients of organic componds

Question 9

Micronutrients

Answer 9

Elements that are required in very small amounts. Typically have catalytic functions as cofactors of enzymes

Question 10

Rhizobacteria

Answer 10

Bacteria that live in close associated with plant roots or in the rhizosphere

The bacteria depend on nutrients such as sugars, amino acids and organic acids that are secreted by plant cells. In return, the bacteria can produce antibiotics, absorb toxic metals, or make nutrients more available to roots.

Question 11

Rhizosphere

Answer 11

The soil region close to a plant’s roots and characterized by a high level of microbiological activity

Question 12

Nitrogen Cycle

Answer 12

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 the cycle begins again

Question 13

Nodules

Answer 13

A swelling on the root of a legume. Nodules are composed of plant cells that contain nitrogen-fixing bacteria of the genus rhizobium

Question 14

Bacterioid

Answer 14

A form of the bacterium rhizobium contained within the vesicles formed by the floor cells of a root nodule.

Question 15

Crop Rotation

Answer 15

The practie of growing different crops in succession on the same land cheifly to preserve the productive capacity of the soil.

Question 16

Mycorrhiza

Answer 16

the intimate mutualistic assocaitions of roots and fungi

The fungus increased the surface area for water intake and supplies the plant with phosphorus and other minerals absorbed from the soil. They also can secrete growth factors that stimulate root growth and branching as well as antibiotics.

Question 17

Ectomycorrhiza

Answer 17

Association of a fungus with a plant root system in which the fungus surrounds the root but does not cause invagination of the host cell’s plasma membrane

Question 18

Arbuscular Mycorrhiza

Answer 18

Associations of a fungus with a plant root system in which the fungus causes the invagination of the host cell’s plasma membranes