Chapter 37: Soil and Plant Nutrition

Question 1

Humus

Answer 1

Remains of dead organisms and other matter; found in A horizon of soil

Question 2

Topsoil; loans

Answer 2

Found in A horizon of soil, mainly consists of loans, roughly equal mixtures of clay, silt, and sand

Question 3

Leaching

Answer 3

Perforation of water through soil that results in loss of many nutrients. Most soil nutrients are negatively and do not bind to anions.

Question 4

Cation exchange

Answer 4

When cations are displaced by other cations, particularly H+ by roots

Question 5

Why do plants prefer acidic soil? What do we add to lower/raise the pH?

Answer 5

Acidic soil facilitates cation exchange; sulfate is added to lower the pH; lime is added to raise the pH.

Question 6

What happens when soil pH dips below 5?

Answer 6

Toxic Al3+ ions become more soluble, and are taken up by plants, stunting growth.

Question 7

No-till agriculture

Answer 7

No-till agriculture: a plowing technique in which a special plow creates narrow furrows for seeds and fertilizer

Question 8

Phytoremediation

Answer 8

Phytoremediation: nondestructive biotechnology that harvests the ability of some plants to extract soil pollutants and concentrate them in parts of the plant where it is removed for safe disposal

Question 9

Hydroponic culture

Answer 9

Plants are grown in mineral solutions instead of soil

Question 10

Macronutrients of plants

Answer 10

Nitrogen, Phosphorus, Potassium, Calcium, Carbon, Oxygen, Sulfur, Magnesium, Hydrogen

Question 11

Micronutrients of plants

Answer 11

Manganese, Iron, Chlorine, Zinc, Boron, Copper, Nickel, Molybdenum

Question 12

Why are Na+ ions needed for CAM plants?

Answer 12

Na+ ions are needed for the regeneration of phosphoenolpyruvate

Question 13

Chlorosis

Answer 13

Yellowing of leaves, caused by deficiency of magnesium

Question 14

Where do symptoms show from deficiency?

Answer 14

Deficiency of mobile nutrients usually show symptoms first in older organs, and deficiency of nonmotile nutrients usually show first in younger tissues as older tissues may have storage

Question 15

What can be released by plant roots to lower Al3+ levels?

Answer 15

Malic and citric acid

Question 16

Rhizosphere

Answer 16

Soil closely surrounding plant roots; harbored by rhizobacteria

Question 17

What forms of nitrogen can plants use?

Answer 17

NO3- (nitrate) and NH4+ (ammonium ion)

Question 18

Nitrification

Answer 18

Ammonia is converted to nitrite, then nitrate; often done by nitrifying bacteria

Question 19

Denitrifying bacteria

Answer 19

Convert nitrate back to ammonia

Question 20

Ammonification

Answer 20

Convert atmospheric nitrogen to ammonium

Question 21

Bacteroids

Answer 21

A form resumed by Rhizobium bacteria in nodules of roots; helps limit gas exchange, as Rhizobium functions in anaerobic conditions

Question 22

Leghemoglobin

Answer 22

Red pigment in plant nodules; binds to oxygen reversiblely

Question 23

Crop rotation

Answer 23

Crop rotation: commonly, a nonlegume is planted one year, and a legume is planted the following, to restore the concn of fixed nitrogen in the soil

Question 24

Epiphytes

Answer 24

A plant that grows on another plant; produce and gather own nutrients