Question 1

aeration

Accepted Answer

the exchange of gases in the soil.

Question 2

aeroponics

Accepted Answer

a hydroponics system designed to have plant roots suspended in the air within a closed container.

Question 3

aggregate culture

Accepted Answer

a hydroponics system that involves the use of aggregate or substrate materials that help support the plants.

Question 4

ammonification

Accepted Answer

the conversion of organic nitrogen compounds to ammonia.

Question 5

assimilation

Accepted Answer

the process of plants absorbing nitrogen in the forms of nitrate and ammonia.

Question 6

available water

Accepted Answer

water found in the soil pore spaces that can be absorbed by plant roots.

Question 7

biogeochemical cycles

Accepted Answer

the recycling of nutrients throughout the ecosystem.

Question 8

casparian strip

Accepted Answer

a band, or strip, encircling cells of the endodermis.

Question 9

cation exchange capacity

Accepted Answer

a measure of a soil's capacity to hold nutrients.

Question 10

cations

Accepted Answer

a positively charged ion.

Question 11

denitriification

Accepted Answer

the reduction of nitrate (NO3) to gaseous nitrogen (N2).

Question 12

ecosystem

Accepted Answer

a community of living (biotic) organisms in a nonliving (abiotic) physical environment.

Question 13

endodermis

Accepted Answer

tightly fitting cells that make up the inner-most layer of the cortex.

Question 14

extracellular route

Accepted Answer

a path through the spaces between cells that the greatest volume of water takes as it flows horizontally through the root.

Question 15

fibrous root system

Accepted Answer

a root system characterized by roots roughly the same size and length.

Question 16

hydroponics

Accepted Answer

the growing of plants with their roots in a medium other than soil.

Question 17

immobilization

Accepted Answer

the conversion of nitrogen from inorganic forms to organic forms.

Question 18

inorganic matter

Accepted Answer

matter that is not of plant or animal origin; in soil, weathered rock, which often makes up the largest portion.

Question 19

intracellular route

Accepted Answer

a path water takes through the cells between the epidermis and the xylem of a plant.

Question 20

macronutrients

Accepted Answer

nine of the sixteen essential elements that are required in greater quantity than the others.

Question 21

micronutrients

Accepted Answer

seven essential elements that are needed in small quantities; also called trace elements.

Question 22

mineralization

Accepted Answer

conversion of organic forms of minerals to inorganic forms.

Question 23

napiform roots

Accepted Answer

a root system that is highly specialized for the storage of starches.

Question 24

nitrification

Accepted Answer

the conversion of ammonia to nitrate.

Question 25

nitrogen cycle

Accepted Answer

the circulation of nitrogen from the abiotic environment to living things and back to the abiotic environment.

Question 26

nitrogen fixation

Accepted Answer

a process by which nitrogen gas is converted to ammonia or nitrate.

Question 27

nodule

Accepted Answer

a swelling on the root of a legume in which nitrogen fixation occurs.

Question 28

nutrient film technique

Accepted Answer

a water culture system involving a continuous flow of nutrient solution through a series of tubes, troughs, or channels that wash over plant roots.

Question 29

organic matter

Accepted Answer

decayed or partially decayed remains of plants and animals found in soil.

Question 30

parts per million

Accepted Answer

the measure of molecules in solution.

Question 31

pericycle

Accepted Answer

a layer of cells just to the inside of the endodermis that has meristematic properties and, consequently, is where lateral or branch roots originate.

Question 32

plasmodesmata

Accepted Answer

cytoplasmic channels connecting adjacent cells that allow for the movement of water molecules and ions.

Question 33

primary macronutrients

Accepted Answer

nitrogen, phosphorus, and potassium.

Question 34

rock wool

Accepted Answer

a spongy, fibrous material spun from molten volcanic rock; it is commonly used in hydroponics.

Question 35

secondary macronutrients

Accepted Answer

calcium, magnesium, and sulfur; plants need them in moderate amounts.

Question 36

soil

Accepted Answer

the outer layer of the earth's surface that consists of weathered rock and mineral fragments, decayed or decaying organic matter from plants and animals, water, air, and living organisms

Question 37

soilless medium

Accepted Answer

a growing medium that lacks any mineral soil.

Question 38

substrate

Accepted Answer

a material in which plants take root.

Question 39

symbiosis

Accepted Answer

an intimate relationship between two different species.

Question 40

taproot system

Accepted Answer

a root system that has a main root with numerous adventitious or lateral roots branching off the main root.

Question 41

unavailable water

Accepted Answer

a thin film of water that binds so tightly to the medium's particles that it cannot be used by plants.

Question 42

water culture

Accepted Answer

a hydroponics system that does not use aggregate substrate materials to help support the plants.

Question 43

water-holding capacity

Accepted Answer

the ability of soils to hold water.

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