nutrition and transport in flowering plants Flashcards
structure of a leaf
epidermis, palisade mesohpyll, vascular bundle, spongy mesophyll, air spaces, epidermis, stomata
adaptations to photosynthesis
- waxy cuticle on upper and lower epidermis
- stomata present in the epidermal layers
- chloroplasts containing chlorophyll in all mesophyll cells
- more chloroplasts in upper palisade tissue
- interconnecting system of air spaces in the spongy mesophyll
- veins containing xylem and phloem situated close to mesophyll
how do guard cells
- The guard cells control the opening and closing of stomatal pores by the osmosis
process. - The cell wall surrounding the stoma is thicker than the other parts of the cell wall.
- During the day, the guard cells photosynthesise, causing an increase in glucose
concentration in the cell sap. This in turn lowers the water potential of the cell. - Water then enters the guard cell by osmosis and causes it to be turgid. This causes
the guard cell to curve around the stoma and cause it to widen. - In darkness, the guard cells do not photosynthesise and glucose concentration drops.
This causes the water potential to increase. - Water leaves the guard cells by osmosis, causing them to be more flaccid. This
closes the stoma
entry of carbon dioxide and water into the leaf
- In the day, carbon dioxide in the leaf is rapidly used up for
photosynthesis. This causes the concentration of carbon dioxide in the
leaf to drop. - Thus carbon dioxide diffuses into leaf from the environment.
- Mesophyll cells are covered with a thin layer of moisture on the
surfaces. Some carbon dioxide will dissolve into the water. - This dissolved carbon dioxide will then diffuse into the mesophyll
cells. - Xylem transports water to the leaf from roots
(will be elaborated later in the notes) - Once out of the xylem, water will from
mesophyll cell to mesophyll cell via osmosis.
function of xylem
(1) Conduct water and dissolved mineral salts from roots to all parts of plant.
(2) Provide mechanical support to plant. (lignified walls)
phloem
sieve tube cells
cross-wall with many perforations (sieve plates)
lost most organelles, depend on companion cells for nutrients and energy
function: conduct sucrose and amino acids throughout plant
why need nutrition
raw materials to build new cells and tissues
energy
why photosynthesis important
Photosynthesis makes chemical energy available
to animals and other organisms.
Photosynthesis removes carbon dioxide and provides oxygen during
photosynthesis.
Energy is stored in fossil fuels through photosynthesis.
define photosynthesis
process which light energy absorbed by chlorophyll is transformed into chemical energy, used in synthesis of carbohydrates from water and carbon dioxide, while oxygen is liberated
test for starch
destarch the plant (leave in dark for 48h)
1. boil leaf for 30 seconds
2. boil leaf in ethanol in hot water
3. dip in warm water to remove ethanol and soften
4. spread of white tile and drop iodine solution
limiting factor format
As light intensity increases
from 0 to 4 relative units, rate
of photosynthesis increases
from 0 to 1.9 relative units.
Light intensity is the limiting
factor.
As light intensity increases
from 4 to 7 relative units, rate
of photosynthesis remains
constant at 1.9 relative units.
Other factor(s) is/ are the
limiting factors (e.g. carbon
dioxide concentration).
fate of glucose
why?
turned into other carbohydrates, lipids or proteins
since glucose is small, soluble, dissolvable, thus is highly reactive and not suitable for transport
water movement in root
passes from root hair to cortical cell to next cortical cell … to xylem vessels
definition of transpiration pull
Transpiration provides a suction force, which is the main factor that causes movement of
water up xylem
2 forces of capillary action
cohesion btwn water molecules
adhesion of water molecules on surface of tubes
3 definitions of the transpiration shit
transpiration = loss of water vapour from aerial parts of plant, especially through stomata of leaves
transpiration stream = stream of water up a plant
transpiration pull = suction force due to transpiration
transpiration pull format
Water continuously moves out of the
mesophyll cells to form a thin film of
moisture over their surfaces.
Water evaporates from this thin film of
moisture and moves into the intercellular
air spaces. Water vapour accumulates
in the large air spaces near the stomata
(sub-stomatal air spaces).
Water vapour then diffuses through the
stomata to the drier air outside the leaf.
This is transpiration.
This results in transpiration pull, a
suction force which pulls the whole
column of water up the xylem vessels.
As water evaporates from the mesophyll
cells, the water potential of the cell sap
decreases. The mesophyll cells begin to
absorb water by osmosis from the cells
deeper inside the leaf. These cells, in
turn, remove water from the veins, that
is, from the xylem vessels.
importance of transpiration
draws water and mineral salts from root to all parts of plant
removes thermal energy and cooling the plant
factors affecting transpiration (increase)
less humid
more wind
higher temp
higher light intensity
wilting pros and cons
Advantage: When leaf folds up, surface area exposed to sunlight is reduced. This causes
guard cells to become flaccid and stomata to close, rate of transpiration reduced.
Disadvantage: Rate of photosynthesis is reduced because water becomes a limiting
factor. As stomata are closed, volume of CO2 entering leaf is also reduced. CO2
becomes a limiting factor. Rate of photosynthesis is decreased.
