Transport in Plants (Revised) Flashcards
1
Q
Function of xylem
A
- conducts water and dissolved mineral salts frm roots to stems
- mechanical support
2
Q
What xylem tissues are made up of
A
- many xylem vessels
- long hollow tube
- made up of many dead cells
- collectively need to remain turgid to keep plant upright
3
Q
How the xylem vessel is adapted for its function
A
- inner walls thickened with lignin (hard and rigid)
- prevents collapse of vessel - empty lumen w/o protoplasm
- reduces resistance to water flowing thru
4
Q
Function of phloem
A
- conducts sucrose and amino acids frm leaves/chlorophyll-containing parts to other parts
5
Q
What phloem is made up of
A
- sieve tubes
- companion cells
6
Q
Sieve tubes (Phloem)
A
- contains sieve tube elements/cells and sieve plates
- Sieve tube cells:elongated, thin-walled living cells
- Sieve plates: cross walls with pores
7
Q
Sieve tube cell
A
- mature: thin layer of cytoplasm, no central vacuole, nucleus, most organelles
- each has a companion cell
- carries out metabolic processes to keep sieve tube cell alive
- contains many mitochondria, cytoplasm, nucleus
- provides nutrients and help STC transport sucrose and aa
8
Q
How phloem is adapted for its function
A
- Companion cell has many mitochondria
- provide energy needed to load sucrose and aa frm mesophyll cells into sieve tubes via active transport - Holes in sieve plates
- allow rapid flow of sucrose and aa thru sieve tubes
9
Q
Pith and cortex
A
- store glucose as starch
10
Q
Cambium
A
- mitosis (divide and differentiate)
- form new xylem and phloem cells
- in between xylem and phloem
- thickens stem
11
Q
Epidermis
A
- waxy cuticle greatly reduces rate of evaporation
12
Q
Vascular bundle (stem)
A
- xylem, phloem and cambium
13
Q
Dicotyledonous root
A
- phloem and xylem alternate
- cortex of root is storage tissue
- epidermis –> piliferous layer
14
Q
Root hair cell
A
- tubular outgrowth of an epidermal cell
- thin layer of moisture surrounding it (dilute soln of mineral salts)
- sap relatively concentrated with sugars and salts (lower wp)
15
Q
How root hairs absorb ions/mineral salts
A
- Active transport
- conc of ions in soil soln lower than RHC
- energy obtained frm cellular respiration in RHC - Diffusion
16
Q
How RHC adapted for its function
A
- Long and narrow
- increase SA:V, increase rate of absorption - Cell surface membrane prevents cell sap frm leaking out
- sap contains glucose, aa and salts
- lower wp than soil
- water enter roots via osmosis - RHC contains many mitochondria
- aerobic respiration releases energy for active transport of ions into cell
17
Q
Define root pressure
A
- living cells around xylem vessels in root pump ions in
- decrease wp of xylem vessels
- water moves frm living cells into vessels via osmosis, flow upwards
18
Q
Define capillary action
A
- water molecules form bonds with each other and lignified cell wall
- forces of cohesion and adhesion
- helps move water up narrow tubes
19
Q
Define transpiration
A
- loss of water vapour frm plant mainly thru stomata in leaves
20
Q
How transpiration moves water against gravity
A
- water evaporate frm stomata of leaves
- water removed frm xylem vessels
- suction force aka transpiration pull
- main force in drawing water and mineral salts up the plant
21
Q
How water is removed
A
- Water continuously moves out frm mesophyll cells, form thin layer of moisture
- water evaporate frm thin layer , move into intercellular air spaces
- water vapour accumulate in sub-stomatal air spaces - water vapour diffuses thru stomata into drier air (transpiration)
- water evaporate frm mesophyll cells, wp of cell sap fall, cell absorb water via osmosis frm cells deeper in leaf
- remove water frm xylem vessels - transpiration pull, suction force pulls whole column of water up vessels
22
Q
Why transpiration is impt
A
- Pulls water and mineral salts frm roots to stems and leaves
- Evaporation of water frm cells in leaves remove latent heat of vaporization, cools plant down (wont get scorched)
- Transported to leaves for photosynthesis
- keep cells turgid, mechanical support, allow leaves to spread widely
23
Q
Factors that affect rate of transpiration
A
- Humidity
- Wind/air movement
- Temp of air
- Light
24
Q
Humidity
A
- intercellular air spaces normal saturated with water vapour
- less humid outside leaf, steeper concentration gradient
- vice versa
25
How plants are adapted for desert-like conditions
1. Trichomes: tiny hairs that trap water vapour, increase humidity arnd stomata, decrease rate of transpiration
2. Sunken stomata: water vapour condense back into stomata
3. smaller SA:V of leaves (don't say size)
4. Thicker cuticle
26
Wind/air movement
- wind blows away water vapour accumulated outside stomata
- maintains water vapour conc gradient btwn leaf and atmosphere
- stronger wind, higher rate of transpiration (vice versa)
27
Temp of air
- affects rate of evaporation
| - high temp, higher rate of evaporation, higher rate of transpiration
28
Light
- affects size of stomata
- sunlgiht: stomata will open and become wider
- vice versa
29
Wilting
- turgor pressure in leaf mesophyll cells supports leaf; keeps it firm to spread out widely (why?)
- strong sunlight, rate of transpiration exceeds rate of absorption of water
- cells lose turgor
- become flaccid, plant wilts
30
Advantages of wilting
- S:A exposed to sunlight falls as leaf folds up
- excessive loss of water, guard cells become flaccid, stomata close
- rate of transpiration falls
31
Disadvantages of wilting
- rate of photosynthesis falls as water becomes limiting factor
- stomata closed, amt of CO2 entering leaf reduced
- CO2 becomes limiting factor for photosynthesis, cause rate of photosynthesis to fall
- folding of leaf reduces SA:V exposed to light
32
Translocation
- Source: manufactures glucose
- SInk: need glucose
- can change depending on environment
- bi-directional
33
How respiratory poison works
- dissolves, taken in by xylem
- assimilates into leaf, companion cells in phloem
- cannot respire (mitochondria poisoned), active transport affected
- translocation affected
