Chapter 8 - Transport in plants Flashcards
Define xylem and phloem
plant tissue made up of dead empty cells, joined end to end with no walls between them (tube)
What are the 3 characteristics of the xylem?
- runs from roots through stem into every leaf
- transports water and mineral ions
- helps support the plant
How are the xylem vessels and phloem arranged in the cross section of a root?
In a star (xylem in the middle) and the vessels on the side are the phloem
How are the xylem vessels and phloem arranged in the cross section of a stem?
the phloem are outside of the xylem but each bundle is more seperate
How are the xylem vessels and phloem arranged in the cross section of a stem?
the xylem vessels can be seen on top of the phloem
What are the cell walls and xylem made of?
cellulose and ligrin that are very strong to keep the cell upright
why does the structure of xylem keep the vessels open?
to allow constant flow
what does ligrin do in the leaves?
keeps the leaves flat and open to absorb sunlight
what is the approximate diameter of xylem?
15 µm - 200 µm
Why is xylem narrow?
to prevent bubbles from forming
What does the phloem transfer?
food - sucrose and amino acids
Define vascular bundles
a group of xylem vessels and phloem tubes
What does the root cap do?
protects roots as it grows through the soil
What is most of the root covered by?
epidermis cells
From where are root hair cells formed?
some of the epidermis cells
What is the function of the root hair cells?
absorb water and mineral ions from soil
How long do root hair cells live?
not very long
How does the water get from the soil to the mesophyll in the leaves and where does it pass through?
soil → root hair cells → root cortex cells → xylem → mesophyll cells in leaves
all by osmosis
How does water pass across the roots?
from cell to cell
Why is water drawn up the xylem vesseles?
because transpiration is constantly removing water from the top of them
Define transpiration
loss of water vapor from the leaves
How is water vapor lost in a plant?
Water vapor moves up the root and stem in xylem vessels. Water evaporates from leaves through stomata
What are the 3 characteristics of transpiration pull?
- caused by the loss of water vapor through transpiration
- causes lower pressure at the top of the system, drawing water up
- water moves up the xylem in one direction because of this
Define potometer
an instrument for measuring the amount of water that a plant loses through transpiration
What letter does a potometer look like?
U
How does higher temperature affect the rate of transpiration?
greater kinetic energy of particles = faster evaporation
What 3 factors affect rate of transpiration?
- wind
- temperature
- humidity
How does wind affect photosynthesis?
if there is stronger wind, water vapor is pushed away from the leaf
Why does humidity decrease transpiration?
because there is more water vapor outside of the leaf the inside than leaf
Say if each of the factors that affect rate of transpiration is proportional of unproportional
- temp. (proportional)
- wind (proportional)
- humidity (unproportional)
Define source
part of the plant that releases sucrose / amino acids: usually leaves (photosynthesis)
Define sink
part of the plant that uses or stores sucrose / amino acids: usually roots and flowers
What do roots store?
sucrose as starch
What do flowers use sucrose for?
to make fructose
