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Sec 3 Pure Bio > Transport in plants > Flashcards

Transport in plants Flashcards

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Biology 101 flashcards
1
Q

Identify the 2 type of vascular tissues

A
  • Xylem

- Phloem (sieve tube elements&companion cells)

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2
Q

Functions of xylem

2 pts

A
  • conducts water and dissolved mineral salts from the roots the stem and leaves
  • provide mechanical support for plant
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3
Q

Structure of xylem

6 pts

A
  • made up of many dead cells fused together at the ends to form a long hollow tube (do not contain protoplasm)
  • the hollow tubes are called xylem vessels
  • xylem tissues consist mainly of xylem vessels
  • continuous lumen with no cross-walls or protoplasm
  • lignin deposits in inner walls of xylem vessels
  • lignin deposited in form of rings, spirals, or whole vessel lignified except for regions called pits (diff patterns of lignifications)
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4
Q

Functions of xylem

2 pts

A

-conducts water and dissolved mineral salts from the roots the stem and leaves

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5
Q

Structure of xylem

6 pts

A
  • made up of many dead cells fused together at the ends to form a long hollow tube
  • the hollow tubes are called xylem vessels
  • xylem tissues consist mainly of xylem vessels
  • continuous lumen with no cross-walls or protoplasm
  • lignin deposits in inner walls of xylem vessels
  • lignin deposited in form of rings, spirals, or whole vessel lignified except for regions called pits
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6
Q

Why are there different patterns of lignifications?

2 pts

A
  • annular (rings) and spiral usually younger plants

- pitted usually when plant is older and more matured

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7
Q

Why are there are holes in the lignifications?

2 pts

A
  • transport and to allow water and mineral salts to move out to sides e.g to side branches
  • also move to phloem to help push sucrose down
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8
Q

How is the xylem adapted for its functions?

A
  • empty lumen without protoplasm or cross-walls enables water to move easily thru lumen
  • walls are lignified to prevent collapse of vessels
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9
Q

Function of phloem

A

-transports manufactured food such as sucrose and amino acids from leaves to other parts of plant

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10
Q

Structure of phloem

2 pts

A
  • consists of 2 main types of cells: sieve tube elements and companion cells
  • other cell types present: phloem parenchyma cells and phloem fibres
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11
Q

Structure of sieve tube

5 pts

A
  • elongated cells
  • lack nuclei
  • thin layers of cytoplasm (diff between xylem&sieve tube cells)
  • sieve tube elements made of sieve tube cell joined end to end to form sieve plate in between
  • sieve plates are cross-walls with many small sieve pores
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12
Q

Structure of companion cells

2 pts

A
  • narrow, thin-walled cells
  • contain cytoplasm and numerous mitochondria (aerobic repiration, release energy, needed to transport sucrose and amino acid
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13
Q

Purpose of companion cell

2 pts

A
  • mature sieve tube cells does not have most of its organelles (e.g. central vacuole, nucleus, mitochondria etc)
  • companion cell helps to keep sieve tube cell alive by providing it with nutrients and energy
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14
Q

How is the sieve tube (phloem) adapted for its function?

3 pts

A
  • sieve tube elements have very little protoplasm, arranged to form a continuous column
  • this reduces resistance for flow of substances within phloem
  • pores within sieve plates allow rapid flow of sucrose and amino acids
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15
Q

How is the companion cell (phloem) adapted for its function?
(2 pts)

A
  • companion cells contain numerous mitochondria (aerobic respiration)
  • produce energy to allow sucrose and amino acids to be actively transported to sieve tubes
  • every phloem sieve tube cell has an associated companion cell to ensure its survival
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16
Q

How are vascular tissues organised in stems (arrangement of xylem&phloem)

A

-in a dicotyledonous stem, xylem and phloem grouped tgt to form vascular bundles

17
Q

How are vascular tissues organised in stems (cambium)

4 pts

A
  • phloem lies outside xylem
  • tissue called cambium lies between them
  • cambium cells divide and differentiate to form new xylem and phloem tissues
  • allows thickening of stem
18
Q

How are vascular tissues organised in stems (pith)

A

-vascular bundles arranged a ring around central region called the pith

19
Q

How are vascular tissues organised in stems (outer layer)

2 pts

A
  • stem covered by a layer of cells called epidermis

- epidermal cells protected by waxy, waterproof cuticle (reduces evaporation of water from stem)

20
Q

How are vascular tissues organised in stems (cortex)

2 pts

A
  • cortex is the region between vascular bundle and epidermis
  • both pith and cortex are storage tissues
21
Q

How are vascular tissues organised in roots (arrangement of phloem&xylem)
(2 pts)

A
  • in a dicotyledonous root, xylem and phloem not bundled tgt
  • alternate with each other
22
Q

How are vascular tissues organised in roots (cortex)

3 pts

A

-cortex of root is a storage tissue
-innermost layer of root cortex is called endodermis
(endo=inside, epi=outside)
-endodermis controls what goes into xylem (like a gate)

23
Q

How are vascular tissues organised in roots (outer layer)

2 pts

A
  • epidermis of root is outermost layer of cells

- also known as piliferous layer

24
Q

How are vascular tissues organised in roots (root hair)

2 pts

A
  • each root hair is a tubular outgrowth of an epidermal cell
  • outgrowth increase SA:V of root hair cell
25
Q

Define translocation

4 pts

A
  • the transport of manufactured food substances (sucrose&amino acids) in plants
  • bi-directional
  • food substances can move either down phloem tissues of shoots to roots
  • can also go up the phloem tissues of shoots to leaves
26
Q

Direction of translocation

7 pts

A
  • direction depends on demand and supply of sucrose
  • not all food produced is used by leaves
  • excess glucose stored in storage organs, often in lower portions of plant
  • sucrose&amino acids translocated from leaves to storage area, food move down shoot
  • environmental conditions not favourable, photosynthesis cannot occur optimally (e.g. during winter)
  • storage organ becomes main source of food
  • food translocated from lower parts of plant to higher parts
27
Q

How can translocation be studied?

3 pts

A
  • using aphids
  • “ringing” experiment
  • radioactive isotopes
28
Q

Translocation studies: Using aphids (steps)

A
  1. Anaesthesise aphid with CO2 while it is feeding on stem
  2. Cut off its body such that its proboscis remains in plant tissue
  3. Analyse liquid that exudes from cut end of proboscis
  4. Section the portion of stem that contains the proboscis and examine it under a microscope
29
Q

Translocation studies: Using aphids (why it is necessary to anaesthesise aphids)

A
  • to enable body of aphid to be cut off while aphid is feeding
  • ensures proboscis remains in phloem sieve tube
  • if stylet severed, sap will continue to flow from plant due to hydrostatic pressure within sieve tube
30
Q

Explain how structure of root hair cell helps them to perform their functions in uptake of water&minerals
(3 pts) (Practice paper question)

A
  • each root hair is a tubular outgrowth of an epidermal cell, outgrowth increases SA:V, more water taken in at faster rate
  • RHC have large no. of mitochondria, release energy for active transport of mineral salts (not water)
  • large central vacuole with a cell membrane (tonoplast) prevent leakage of cell sap, increase conc gradient for faster diffusion
31
Q

Explain how water moves thru shoot and into air

3 pts) (Practice paper question

A
  • osmosis occurs from xylem to mesophyll cells and out of cells
  • water evaporates from thin film arnd cells into intercellular spaces
  • water vapour diffuses out of stomata

Sec 3 Pure Bio (16 decks)

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