Topic 10: Plant Physiology

Question 1

What are the different systems involved with plants?

Answer 1

root system

shoot system

Question 2

What are the different organs involved with plants?

Answer 2

roots, stems, leaves

Question 3

What are the characteristics of the shoot system?

Answer 3

above ground
flowers
leaves
fruit
stems

Question 4

What is a characteristic of the root system?

Answer 4

below ground

Question 5

What are the functions of the root system?

Answer 5

anchor to ground
absorb minerals and water
store carbohydrates

Question 6

What do roots have?

Answer 6

root hairs

Question 7

What are root hairs, where are they located and what do they do?

Answer 7

thin, finger-like extensions of root epidermal cells
primarily near tip of elongated roots
used to increase surface area to obtain more nutrients for the plant

Question 8

What are stems and what do they do?

Answer 8

plant organs bearing leaves and buds
elongate and orient shoot to maximize photosynthesis
elevate reproductive structures - increase pollen and seed dispersal
green stems - limited photosynthesis

Question 9

What are leaves and what do they do?

Answer 9

main photosynthetic organ in vascular plants

capture light, gas exchange

Question 10

What is unique to plants?

Answer 10

its tissue system

Question 11

What is the dermal tissue system?

Answer 11

outer protective covering

1st line of defense against physical damage, pathogens

Question 12

What does the dermal tissue system consist of in non-woody plants? Woody plants?

Answer 12

cuticle and epidermis: single layer of tightly packed cells

periderm instead of epidermis

Question 13

What are the dermal tissue functions?

Answer 13

reduce water loss
defend against insects
root hairs: absorb water and minerals
guard cells

Question 14

What are guard cells and what do they do?

Answer 14

specialized cells in leaved

regulate gas exchange by opening and closing the stomata

Question 15

How much of the plant includes the ground tissue system? What does this tissue system do?

Answer 15

most of the plant

includes cells specialized for storage, photosynthesis, support and short distance transport

Question 16

What does the vascular tissue system do?

Answer 16

transport materials throughout plant body

provide mechanical support

Question 17

What are the two types of vascular tissue system?

Answer 17

xylem and phloem

Question 18

What does the xylem do?

Answer 18

conducts water and dissolved minerals upward from roots

Question 19

What does the phloem do?

Answer 19

transport sugars from where made (mostly leaves) to where needed (usually roots and sites of growth)

Question 20

What is the cohesion tension hypothesis?

Answer 20

when the stomata opens and water evaporates out of leaves (transpiration) this cohesion causes a tension which moves water through the xylem

Question 21

What is the order of the water potential gradient?

Answer 21

8. atmosphere
9. stomata
10. leaf ground tissye
11. leaf xylem
12. stem xylem
13. root xylem
14. root tissue
15. soil

Question 22

What kind of movement occurs in the phloem and what is this called?

Answer 22

bidirectional movement = translocation

Question 23

Define source, define sink.

Answer 23

source - area with excess sugar (leaf)

sink - area of storage or metabolism (roots)

Question 24

How does the phloem move?

Answer 24

from source to sink

Question 25

What is the pressure flow hypothesis?

Answer 25

explanation for movements of sugars in phloem
suggests translocation occurs via pressure gradient
at source - high pressure - sugar loaded/ pushed into phloem
at sink - low pressure - sugar pushed out of phloem

Question 26

Define plasmodesmata and what does it do?

Answer 26

cytoplasmic connections between plant cells
allows molecules and ions to pass between cells
important in plants
allows passage w/o going through the cell wall

Question 27

Is plant growth indeterminate or determinate? How does this affect plant growth?

Answer 27

indeterminate
continuous except for dormant periods
keeps growing due to perpetually dividing, unspecialized tissue
growth at meristems

Question 28

What is primary growth and what type of plants does this occur in?

Answer 28

increase length by adding more cells

all plants

Question 29

What is secondary growth and what type of plants does this occur in?

Answer 29

increases girth (circumference) of plant
only woody plants

Question 30

What are hormones and what do they do?

Answer 30

organic compounds, act as chemical messengers

control specific physiological responses in plants (plant growth regulators)

Question 31

What are the general characteristics of hormones?

Answer 31

active at very low concentrations
natural or synthetically produced
each hormone can have multiple effects
hormones interact so it’s hard to tell the cause of one effect

Question 32

Define tropism

Answer 32

directional growth response to an environmental stimulus - often due to hormones
directional

Question 33

What was the first plant hormone discovered?

Answer 33

auxins

Question 34

What is the function of auxins?

Answer 34

causes directional growth toward light

triggers cell elongation

Question 35

Explain phototrophism

Answer 35

light exposure produces auxins at tip
auxins move toward shaded side, then down stem
shaded side elongates
plant bends toward light

Question 36

What do cytokinins do? How do they work?

Answer 36

control cell division and differentiation

stimulate cytokinesis but ONLY with auxin

Question 37

What is the function of abscisic acid?

Answer 37

maintains seed dormancy
increased likelihood that seed only germinates under suitable conditions
when it rains, ABA is washed out and seeds germinate

Question 38

What is the function of ethylene?

Answer 38

promotes fruit ripening
causes triple response to mechanical stress (behavior to avoid obstacles)
3 components of triple response: 
1. slow elongation
2. thicken stem
3. curve, grow horizontally