Module 3- Transport in Plants

Question 1

why do multicellular plants need transport systems?

Answer 1

-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

Question 2

what are vascular bundles?

Answer 2

xylem and phloem

Question 3

what is the structure and function of vascular bundles in the stem?

Answer 3

vascular bundles around the edge to give strength and support

Question 4

what is the structure and function of vascular bundles in the roots?

Answer 4

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)

Question 5

what is the structure and function of vascular bundles in the leaf?

Answer 5

vascular bundles in the large central vein to help support structure of the leaf

Question 6

what is the structure of a xylem vessel?

Answer 6

-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

Question 7

what is the function of the xylem?

Answer 7

-transport of water and mineral ions from the roots to shoots and leaves
-maintains structural support in plant
-food storage

Question 8

what ways can lignin be present in xylem?

Answer 8

-spiraled
-rings
-solid tubes with undignified bordered pits which is where water leaves the xylem and moves into other areas of the plant

Question 9

what is the function of the phloem?

Answer 9

-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

Question 10

what is the structure of the phloem?

Answer 10

-sieve tube elements
-companion cells
-sieve plates

Question 11

what direction does phloem transport solutes?

Answer 11

up AND down the plant

Question 12

what are sieve plates?

Answer 12

-found in the areas which are between the joined cells of phloem
-allows for continuous flow of organic compounds

Question 13

what are sieve tube elements?

Answer 13

hollow area between two sieve plates

Question 14

what are companion cells?

Answer 14

-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

Question 15

what is plasmodesmata?

Answer 15

microscopic channels through cellulose wall linking the cytoplasm of adjacent cells

Question 16

what are the structural differences between xylem and phloem?

Answer 16

-xylem are non-living, phloem are living
-xylem walls are lignified, phloem not

Question 17

what are the structural similarities between xylem and phloem?

Answer 17

-both made up of cells joined end to end
-both lack nuclei
-both made up of more than one cell type

Question 18

what are the functional differences between xylem and phloem?

Answer 18

-xylem transport water+mineral ions, phloem transports assimilates

Question 19

what are the functional similarities between xylem and phloem?

Answer 19

-solutes carried in solution in both
-both carry mineral salts

Question 20

what are xerophytes?

Answer 20

plants with adaptations which enable them to survive in dry habitats or habitats where water supply is low

Question 21

what are hydrophytes?

Answer 21

plants with adaptations that enable them to survive in very wet habitats resulting in permanently saturated soil

Question 22

what are some adaptations of water lilies (hydrophytes)?

Answer 22

-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

Question 23

what are some adaptations of cacti (xerophytes)?

Answer 23

hairy leaves
-trap a layer of water vapor

Question 24

what is the major problem for all hydrophytes?

Answer 24

water-logging

Question 25

what are some adaptations of marram grass (xerophytes)?

Answer 25

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