transport systems Flashcards
define herbaceous plants
plants that have non-woody stems
what are the reasons for multicellular plants needing transport systems?
- 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
define dicotyledonous plants
produce seeds containing two cotyledons that act as food stores for developing embryo + form first leaves when the seed germinates
define vascular system
system of transport vessels running through the stem, roots and leaves
define vascular bundles
vascular system of herbaceous dicots made up of xylem and phloem tissue
name 2 types of transport vessels in vascular bundles
- xylem
- phloem
where are the vascular bundles located in the stem?
around the edge
- gives strength and support
where are the vascular bundles located in the roots?
in the middle
- help plant withstand tugging strains that result as stems and leaves and blown in the wind
where are the vascular bundles located in the leaves?
midrib of the dicot leaf is main vein carrying vascular tissue
- helps support structure
- smaller veins branch for transport + support
state the function of the xylem and the phloem
- xylem: transport water and minerals up, support
- phloem: transport of assimilates to all cells of the plant
describe the structure of the xylem
- composed of xylem vessel elements and parenchyma cells
- long hollow tubes
explain 3 ways the xylem is adapted for its function
- 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
describe patterns of lignification in xylem and state its function.
- rings, spirals or solid tubes with small unlignified areas - bordered pits
- support to withstand pressure changes as water moves thru plant
define sieve tube element
main cells of phloem that have no nucleus
- sieve plates form between cells
define sieve plate
perforated walls between phloem cells that form gaps
- ‘sieve-like’ appearance to allow contents to flow through
define companion cell
active cells found next to sieve tube elements
- supply phloem vessels with metabolic needs
describe the structure of the phloem
- 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
describe adaptations of the phloem
- 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
compare the similarities between structure and function of the xylem and phloem
- both transport materials around plant
- both made up of cells joined end to end forming long hollow structures
compare the differences between structure and function of the xylem and phloem
- 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
describe 5 functions of water in plants
- 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
