9. Plant Biology

Question 1

9.1 Why are stomata neccasary?

Answer 1

The waxy cuticle of the plant has low permeability

Question 2

9.1 What are guard cells?

Answer 2

Cells around stomata that open and close it, swollen with water= open, contracted = less water

Question 3

9.1 Draw a xylem structure

Question 4

9.1 What is in the xylem walls to thicken it?

Answer 4

Lignin

Question 5

9.1 Properties of water that are important for plants:

Answer 5

Adhesion: attracted to hydrophillic xylem walls
Cohesion: sticks to one another (chain)

Question 6

9.1 Describe the process of evaporation in the xyelm.

Answer 6

Water evaporates from the leaf surface and adhesion draws water from the nearest source: xylem. This lowers the water pressure and water is drawn up.

Question 7

9.1 What does the xylem move?

Answer 7

Water and ions

Question 8

9.1 What are halophytes?

Answer 8

Plants adapted to salty conditions
-cellular sequesterations within cell walls or vacuoles
tissue partitioning
root level exclusion
- salt excretion

Question 9

9.1 What are xerophytes?

Answer 9

Plants that tolerate dry conditions
-rolled leaves
-reduced leaves
-thick cuticle
-stomata in pit
-low growth

Question 10

9.1 How is water replaced in the xylem

Answer 10

Water is drawn into epidermis root hair cells. From there it either takes the symplast (through cytoplasm) or apoplast pathway (cell wall). The apoplast pathway stops at the casparian strip at the endodermis cell. From there it passes through plasmodesma into the pericyle then the xylem.

Question 11

9.2 What is the process of the phloem?

Answer 11

Translocation

Question 12

9.2 What is the structure of the pholem?

Answer 12

Made up of living sieve tube cells seperated by sieve plates, accompind by companion cells

Question 13

9.2 Draw a phloem

Question 14

9.2 What is translocation

Answer 14

The movement of organic compounds from sources to sinks

Question 15

9.2 Examples of sources

Answer 15

Photosynthetic tissue
Unloading storage

Question 16

9.2 Examples of sinks

Answer 16

Roots
Growing plant

Question 17

9.2 Osmotic pressure at sinks vs sources.

Answer 17

At sources, high concentrations of solute draw in lots of water = high pressure
At sinks, solutes are withdrawn so water is low pressure, goes back to xylem

Question 18

9.2 What carbohydrate is in sap?

Answer 18

Sucrose, not easily metabolized: good transport form

Question 19

9.2 How does phloem loading for sucrose work (2 methods)?

Answer 19

Symplast route: Sugar producting cell and companion cell are connected with plasmodesmata (simple diffusion)

Apoplast: There is a space called the apoplast between the two cells. Simple diffusion from producer into space. From there a H+ pump pushes H+ into the apoplast and a Sucrose-H+ cotransport pump puts them into the companion cell (following H+ gradient)

Question 20

9.2 How to identify phloem vs xylem?

Answer 20

Xylem are always more internal

In roots xylem may form an x, in stem they may be separated by cambian strip

Question 21

9.2 Properties of sieve cells

Answer 21

1) No nucleus
2) Limited cytoplasm
3) Companion cells

Question 22

9.3 Specifics of plant growth

Answer 22

Most plant experience indeterminate growth
- Have totipotent cells capable of any cell type

Question 23

9.3 Draw and label a seed

Question 24

9.3 What is a meristem?

Answer 24

Plant tissue that remains embryonic (undifferentiatted)

Apical:
- length growth
-tips of roots and stems

Lateral
- wideth
- in between xylem/phloem
- bark

Question 25

9.3 What are cytokinins?

Answer 25

Key plant growth hormones, promote cell division (w/auxin)
- promote lateral bud formation
- root apical meristem

Question 26

9.3 What affects rate and direction of growth?

Answer 26

Phototropism and gravitropism

Question 27

9.3 What is auxin?

Answer 27

A plant growth hormone. It activates proton pumps in cell walls and the resulting decrease in pH causes cellulose to expand, influx of water causes cell to stretch

PIN3 protiens transport auxins

Question 28

9.3 Resulting auxin growth

Answer 28

Phototropism: Auxins are transported to dark side, plant tilts towards light (stimulate elongation)

Gravitopism: Auxins on bottom inhibit growth

Question 29

9.4 Process to begin flowering.

Answer 29

OG plant = vegetative structures

The change to reproductive involves meristem at shoot apical

Question 30

9.4 Light response hormone

Answer 30

Phytodrome switches between Pr ( inactive ) and Pfr (active)

Red or white light changes it into an active form, in darkness it slowly returns to the more stable Pr form.

Question 31

9.4 Long day plants vs short day plants

Answer 31

Long day plants (early summer): Large amounts of Pfr bind to receptors to transcript flowering gene (receptors promote)

Short-day plants (fall): Receptors inhibit gene, little Pfr = receptor isn’t active

Question 32

9.4 How does fertilization work?

Answer 32

The pollen grain lands on the surface of the stigma. A pollen tube is produced to connect the two and the male gamete travel down it.

Question 33

9.4 What is needed for seed germination?

Answer 33

O2: Respiration
Water: Metabolically activate
Temp: Activates enzymes
pH: suitable

Question 34

9.4 Label the flower of a plant

Question 35

9.4 What are the steps of reproduction

Answer 35

1) pollination
2) fertilization
3) seed dispersal

Question 36

9.4 Monocots vs dicots angiospermophyta

Answer 36

Monocots
- one cotyledon (Seed)
- upper and lower epidermis stomata
- fiberous roots
- scattered vascular
- parallel veins
- flowers in multiples of 3

Dicots
- two cotyledon
- tap roots
- ringed vascular
- net-like leaves
- 4 or 5 flower petals