Module 3:Transport in Plants Flashcards
Need for transport system and the xylem
What are the 3 main reasons why multicellular plants need transport systems?
metabolic demands-
size
surface area:volume ratio
Why are the metabolic demands of plants high?
3
(think in terms of ability to photosynthesise , hormones and mineral ion transport)
1)the cells of green plants make their own glucose and oxygen through photosynthesis , however many internal/underground parts don’t so need these transported to them and waste products removed
2)hormones made in one part of the plant need to go to areas of the plant where they have an effect
3)mineral ions absorbed by roots need to be transported to cells to make proteins needed for enzymes/cell structure
Explain why the size of plants means they require transport systems
1 point
because plants continue to grow through out their life they need a system that moves substances up and down from roots to leaves quickly
Why does SA:V ratio mean plants require a transport system?
1 point
due to the size and complexity of plants , when stems trunks and roots are taken into account they still have a relatively small SA:V so can’t rely on diffusion alone to supply their cells with what they need
What is the vascular system in plants?
In herbaceous dicots , what are 2 main types of transport vessel?
the series of transport vessels running through the stems , roots and leaves of dicotyledonous plants
xylem and phloem
How are the xylem and phloem arranged in the stem , leaves and roots of plants?
in vascular bundles
What are the 2 major functions of the xylem ?
Is the xylem a living/non living tissue?
-transport of water and mineral ions
-support
its a largely non living tissue
What is the direction of flow of substances in the xylem?
from the roots to the shoots and leaves
What is the structure of xylem VESSELS?
4 points
they are long hollow structures made by several columns of cells fusing together end to end
-they have no end walls that allow a continuous unbroken flow of water
What are the 2 other tissue types associated with the xylem and what do they do?
(also state the structure of the 2nd tissue type)
Thick walled xylem parenchyma -packs around xylem vessels , stores food and tannin deposits
Xylem fibres
-long cells with lignified secondary walls , provide extra mechanical strength but don’t carry water
What is tannin and what does it do?
a bitter tasting chemical that protects plant tissues from attack by herbivores
Name the three ways lignin can be laid down in xylem vessel walls
-can form rings
-can form spirals
-can form solid tubes with many small unlignified areas
What is the name given to the small unlignified areas within the xylem vessel walls and what do they do?
bordered pits
this is where water leaves the xylem and moves into other cells of the plant
