3.1.3 transport in plants

why do plants need transport systems?

• metabolic demands

• SA:V

• size

why do plants need transport systems because of their metabolic demands?

• many internal and underground parts do not photosynthesis

• they need glucose and oxygen transporting to them and need to remove waste products

why do plants need transport systems because of their SA:V?

• plants can’t rely on diffusion alone to supply cells with what they need

• although leaves have relatively hight SA:V

• when stems and roots are taken into account they have low SA:V

why do plants need transport systems because of their size?

• many plants can get very large and so need a substantial transport system

what are dicotyledonous plants?

• plants that produce seeds that contain 2 cotyledons

• these act as food stores for developing embryo to form the first leaves after germination

• they have vascular system made up of xylem and phloem

what is the difference in number of cotyledons in monocots and dicots?

• monocot has 1 cotyledon

• dicot has 2 cotyledons

what is the difference in leaves of monocots and dicots?

• monocots have long, narrow leaves and veins are parallel

• dicots have broad network of veins

what is the difference in vascular bundles of monocots and dicots?

• monocots have scattered vascular bundles

• dicots have a ring of vascular bundles

what is the difference in flower parts of monocots and dicots?

• monocots have flower parts in multiples of 3

• dicots have flower parts in multiples of 5 or 4

what is the function of the xylem?

• transports water and minerals

• support the plant

how is lignin arranged in the xylem?

• lignin is arranged in spiral or small rings

why is lignin arranged in spiral or small rings?

• allows for flexibility

why is there pits in the cell wall, where there is no lignin?

• so that other cells can be provided with water and mineral ions

• to allow lateral movement of water between xylem cells, in case their is blockage/damage

what are the only living cells in xylem called?

• thick walled xylem parenchyma

what does thick walled xylem parenchyma do?

• packs around xylem cells, storing food and tannin deposits

what is tannin?

• chemical that protects plant tissue from attacks by herbivores

• since it tastes really bad

what is the sink in the summer in plants?

• roots turn glucose into insoluble starch to store over the winter

what is the source in plants and when?

• summer/ autumn, the leaf makes glucose by photosynthesis and loads up the phloem to send it to the roots

• spring, the roots hydrolyse starch back into glucose and sends it up to growing parents of the the plant

what is the structure of sieve tube elements?

• have no nucleus

• very little cytoplasm and organelles

what is the structure of companion cells?

• large nucleus

• lots of mitochondria to help load assimilates (sucrose and amino acids) into sieve tubes

what are the cytoplasm of the sieve tube and companion cells connected by?

• plasmodesmata

which way does phloem sap move, when moving through pores in the wall between sieve tubes?

• vertically

where is the xylem found in the roots on a cross sectional?

• central core of xylem often in shape of an X

where is the phloem found in the roots on a cross sectional?

• phloem is found in between the arms of the X

where is the endodermis found in the roots on a cross sectional?

• layer of cells around the vascular bundle

where is the pericycle found in the roots on a cross sectional?

• inside the endodermis is a layer of meristems

where in the steam are the vascular bundles found?

• near the outer edge of the stem to act as scaffolding

what is the layout of the vascular bundles in the stem?

• xylem on inside of each vascular bundle

• phloem towards the outside

• in middle is layer of cambium

what is cambium?

• meristem tissue that divide to produce new xylem and phloem

how do vascular bundles look in the leaf?