transport systems

Question 1

define herbaceous plants

Answer 1

plants that have non-woody stems

Question 2

what are the reasons for multicellular plants needing transport systems?

Answer 2

• size: transport substances from root to leaves - can be large distance
• small surface area: volume ratio
• high metabolic rate: underground parts do not photosynthesis
• direct diffusion is too slow to meet their metabolic needs

Question 3

define dicotyledonous plants

Answer 3

produce seeds containing two cotyledons that act as food stores for developing embryo + form first leaves when the seed germinates

Question 4

define vascular system

Answer 4

system of transport vessels running through the stem, roots and leaves

Question 5

define vascular bundles

Answer 5

vascular system of herbaceous dicots made up of xylem and phloem tissue

Question 6

name 2 types of transport vessels in vascular bundles

Answer 6

• xylem
• phloem

Question 7

where are the vascular bundles located in the stem?

Answer 7

around the edge
- gives strength and support

Question 8

where are the vascular bundles located in the roots?

Answer 8

in the middle
- help plant withstand tugging strains that result as stems and leaves and blown in the wind

Question 9

where are the vascular bundles located in the leaves?

Answer 9

midrib of the dicot leaf is main vein carrying vascular tissue
- helps support structure
- smaller veins branch for transport + support

Question 10

state the function of the xylem and the phloem

Answer 10

• xylem: transport water and minerals up, support
• phloem: transport of assimilates to all cells of the plant

Question 11

describe the structure of the xylem

Answer 11

• composed of xylem vessel elements and parenchyma cells
• long hollow tubes

Question 12

explain 3 ways the xylem is adapted for its function

Answer 12

• long, tube-like structures joined end to end
• no end walls, making continuous tube allowing water to pass up easily
• cells are dead, so have no cytoplasm, reducing resistance + friction of water flow
• walls are thickened with lignin - supports xylem vessels + prevents collapse
• lignin increases as cell gets older
• water + ions move through vessels through small pits where there is no lignin

Question 13

describe patterns of lignification in xylem and state its function.

Answer 13

• rings, spirals or solid tubes with small unlignified areas - bordered pits
• support to withstand pressure changes as water moves thru plant

Question 14

define sieve tube element

Answer 14

main cells of phloem that have no nucleus
- sieve plates form between cells

Question 15

define sieve plate

Answer 15

perforated walls between phloem cells that form gaps
- ‘sieve-like’ appearance to allow contents to flow through

Question 16

define companion cell

Answer 16

active cells found next to sieve tube elements
- supply phloem vessels with metabolic needs

Question 17

describe the structure of the phloem

Answer 17

• long hollow tubes made of living cells - consist of sieve tube elements & companion cells
• sieve tube elements form tube to transport assimilates
• sieve plates in between sieve tube elements
• companion cells linked to sieve tube elements by plasmodesmata, fulfill metabolic needs of sieve tube elements as have lost normal cell functions + no nucleus

Question 18

describe adaptations of the phloem

Answer 18

• sieve tube elements - no nucleus & no/small amount cytoplasm to allow easy transport of assimilates
• sieve plates allow assimilates to pass thru phloem tubes
• plasmodesmata between companion cells, lots of mitochondria & dense cytoplasm in companion cells, to allow them to fulfill metabolic needs

Question 19

compare the similarities between structure and function of the xylem and phloem

Answer 19

• both transport materials around plant
• both made up of cells joined end to end forming long hollow structures

Question 20

compare the differences between structure and function of the xylem and phloem

Answer 20

• xylem: largely non-living tissue, phloem living
• xylem transports water & mineral ions, phloem transports organic solutes
• xylem: flow of materials = roots to shoots + leaves, phloem = up and down
• xylem cell walls lignified, phloem cell walls not

Question 21

describe 5 functions of water in plants

Answer 21

• turgor pressure from osmosis provides hydrostatic skeleton - support stem and leaves
• turgor drives cell expansion: enables plant roots to force way through terrain
• transpiration cools plants down
• mineral ions + assimilates are transported in water
• raw material in photosynthesis