Module 3- Transport in Plants Flashcards
why do multicellular plants need transport systems?
-there is a long distance from external surface to where substances are needed in cells
-diffusion alone would be to slow to transport substances to plant e.g. glucose and remove waste product
-underground parts of plant cannot photosynthesise so TS needed to transport oxygen and glucose
-long distance source to sink
what are vascular bundles?
xylem and phloem
what is the structure and function of vascular bundles in the stem?
vascular bundles around the edge to give strength and support
what is the structure and function of vascular bundles in the roots?
vascular bundles in the middle to help plant withstand tugging strain from stem and leaf blowing in the wind (xylem shaped like X with phloem surrounding)
what is the structure and function of vascular bundles in the leaf?
vascular bundles in the large central vein to help support structure of the leaf
what is the structure of a xylem vessel?
-lignified secondary walls to provide extra mechanical strength— do not transport water
-made up of dead cells
-long hollow structures made by columns cells fusing together end to end
what is the function of the xylem?
-transport of water and mineral ions from the roots to shoots and leaves
-maintains structural support in plant
-food storage
what ways can lignin be present in xylem?
-spiraled
-rings
-solid tubes with undignified bordered pits which is where water leaves the xylem and moves into other areas of the plant
what is the function of the phloem?
-transports food in the form of organic solutes (assimilates) around the plant from the leaves where they are made by photosynthesis
-supplies cells with sugars and amino acids needed for cellular respiration
what is the structure of the phloem?
-sieve tube elements
-companion cells
-sieve plates
what direction does phloem transport solutes?
up AND down the plant
what are sieve plates?
-found in the areas which are between the joined cells of phloem
-allows for continuous flow of organic compounds
what are sieve tube elements?
hollow area between two sieve plates
what are companion cells?
-linked to sieve tube elements by many plasmodesmata
-control the metabolism of their associated sieve tube member
-play a role in loading and unloading of sugars into the phloem
what is plasmodesmata?
microscopic channels through cellulose wall linking the cytoplasm of adjacent cells
they link the companion cell to sieve tube elements
what are the structural differences between xylem and phloem?
-xylem are non-living, phloem are living
-xylem walls are lignified, phloem not
what are the structural similarities between xylem and phloem?
-both made up of cells joined end to end
-both lack nuclei
-both made up of more than one cell type
what are the functional differences between xylem and phloem?
-xylem transport water+mineral ions, phloem transports assimilates
what are the functional similarities between xylem and phloem?
-solutes carried in solution in both
-both carry mineral salts
what are xerophytes?
plants with adaptations which enable them to survive in dry habitats or habitats where water supply is low
what are hydrophytes?
plants with adaptations that enable them to survive in very wet habitats resulting in permanently saturated soil
what are some adaptations of water lilies (hydrophytes)?
-floating leaves are thin, flat + have large air spaces inside to give them buoyancy
-this keeps them close to the surface of the water where there is more light for photosynthesis
-stomata located on the upper surface of the leaves
-this allows for gas exchange to occur with the air instead of the water
-reduced veins in leaves as there is no need to transport water through the plant
what are some adaptations of cacti (xerophytes)?
hairy leaves
-trap a layer of water vapor
what is the major problem for all hydrophytes?
water-logging
what are some adaptations of marram grass (xerophytes)?
hairy leaves
-trap a layer of water vapor creating a higher water potential gradient outside the stomata which reduces the water potential gradient so reducing the evaporation of water from the leaf minimizing water loss via transpiration
