Plant Nutrition and Transport

Question 1

What do leaves, stems and roots do?

Answer 1

leaves: gather sunlight and Co2
stems: supporting structures for leaves and conduits for long distance transport of water and nutrients
roots: mine soil for water and minerals and anchor the plant

Question 2

How does natural selection affect plant ecology?

Answer 2

Plant architectures have been fine-tuned to the ecological niche in which theyre found.

Question 3

What are the two compartments of plant tissues?

Answer 3

Apoplast: everything outside the plasma membrane

Symplast: the cytosol and connecting plasmodesmata

Question 4

What controls the direction of water movement? What is it?

Answer 4

Water potential, a quantity that includes solute concentration and physical pressure.

Question 5

What makes plant cells turgid?

Answer 5

The osmotic uptake of water by plant cells and the internal pressure that builds up.

Question 6

How does long distance transport occur?

Answer 6

Bulk flow, the movement of liquid in response to a pressure gradient.

Question 7

Where does bulk flow occur?

Answer 7

The tracheids and vessel elements of the xylem, and within the sieve elements of the phloem.

Question 8

What are macronutrients?

Answer 8

Elements required in relatively large amounts, including carbon, oxygen, hydrogen, nitrogen, etc.

Question 9

What are micronutrients?

Answer 9

Elements required in relatively small amounts, typically have catalytic functions as cofactors of enzymes.

Question 10

What kind of nutritional deficiencies are most common?

Answer 10

Macronutrient deficiencies of nitrogen, phosphorous, and potassium.

Question 11

What determines soil particle size and what effect does this have?

Answer 11

Soil particle size is determined by the breakdown of rocks, and affects the availability of water, oxygen, and minerals in the soil.

Question 12

What does soil composition refer to?

Answer 12

The inorganic and organic components. Topsoil is a complex ecosystem with fungi, bacteria, animals, and the roots of plants.

Question 13

Where do rhizobacteria get energy from?

Answer 13

The rhizosphere: the region of soil in the vicinity of plant roots in which the chemistry and microbiology is influenced by their growth, respiration, and nutrient exchange.

Question 14

Where does the rhizophere get its energy from?

Answer 14

Plant secretions

Question 15

What are rhizobacteria?

Answer 15

Free-living bacteria that produce antibiotics and make nutrients more available for plants.

Question 16

________ bacteria convert atmospheric nitrogen to nitrogenous minerals that plants can absorb.

Answer 16

Nitrogen fixing.

Question 17

What are mycorrhizae?

Answer 17

Mutualistic associations formed between roots and certain soil fungi that aid in absorption of minerals and water.

Question 18

Where do parasitic plants get nutrition from?

Answer 18

They absorb nutrients through the host plants.

Question 19

Where do carnivorous plants get nutrition from?

Answer 19

Their diet is supplemented by mineral nutrition from digesting animals.

Question 20

How does water and minerals from the soil reach the plant?

Answer 20

They enter the plant through the epidermis of the roots, cross the root cortex, and then pass into the vascular cylinder by way of the selectively permeable cells of the endodermis. From the vascular cylinder, the xylem sap is transported long distances by bulk flow to the veins that branch throughout each leaf.

Question 21

Describe the cohesion-tension hypothesis

Answer 21

Movement of xylem sap is driven by a water potential diffference created at the leaf end of the xylem by the evaporation of water from leaf cells. Evaporation lowers the water potential at the air-water interface, thereby generating the negative pressure that pulls water through the xylem.

Question 22

What is transpiration?

Answer 22

The loss of water vapor from plants.

Question 23

Why does wilting occur?

Answer 23

When water lost by transpiration is not replaced by absorption from the roots.

Question 24

What is the mechanism of how guard cells open stomatal pores?

Answer 24

By the uptake of Potassium.

Question 25

What is the opening and closing of stomata controlled by?

Answer 25

Light, CO2, the drought hormone abscisic acid and a circadian rhythm.

Question 26

What are adaptations to arid environments?

Answer 26

Reduced leaves and CAM photosynthesis.

Question 27

What are the main sources of sugar?

Answer 27

Mature leaves, some storage organs may be seasonal sources.

Question 28

What are the main sugar sinks?

Answer 28

Roots, stems and fruits.

Question 29

What is phloem?

Answer 29

The vascular tissue in plants that conducts sugars and other metabolic products downward from the leaves

Question 30

What does phloem loading depend on?

Answer 30

Active transport of sucrose.

Question 31

How is sucrose transported?

Answer 31

Cotransported with H+, which diffuses down a gradient generated by proton pumps. Loading of sugar at the source and unloading at the sink maintain a pressure difference that keeps sap flowing through the sieve-tube.

Question 32

What is a sieve tube?

Answer 32

a series of sieve tube elements (highly specialised type of elongated cell in the phloem tissue of flowering plants) placed end to end to form a continuous tube