Transport Flashcards
purpose of xylem
carry water + mineral ions from the roots up the shoot to leaves in transpiration system
also supports plant due to lignin in it‘s walls
phloem purpose
transports sucrose + amino acids from sources -> sinks
this movement of substances around the plant is called translocation
purpose of root hair cell
root hair cell absorbs water and inorganic/ mineral ions from soil.
the root hair increases surface area over which water + mineral ions can be absorbed
water is absorbed by osmosis through the partially permeates membrane of the root hair cell from the soil, where it is in higher concentration.
transporation
is the evaporation of water at the surfaces of the mesophyll cells into the air spaces followed by loss of water vapour from the stomata.
how do you test a leaf for starch?
1) dip the leaf into boiling water for one minute. this breaks open the cell wall and cell membranes.
2) place leaf into a test tube of ethanol or methylated spirits and put the test tube into a hot water bath for 10 minutes. the alcohol will dissolve the chlorophyll out of the leaf so it is now white but brittle.
3) remove leaf from test tube and dip leaf into warm water for a few minutes. this will soften the brittle leaf.
4) remove leaf from water and spread out on a tile or dish and add iodine solution using a dropper to test for presence of starch.
how do you show that light is necessary for photosynthesis?
1) take a potted plant that is well watered and has been de-starched.
2) cover a part of one of it‘s leaves with dark paper, attached using two paper clips.
3) place the potted plant into a well-lit area for 2-6 hours.
4) the paper is removed and the leaf is tested for starch
what is the conclusion if the covered leaf experiment?
starch is only present in areas that received light, showing that light is necessary for photosynthesis
how do you show that carbon dioxide is necessary for photosynthesis?
set up two bell jars. cover both well watered, de starched plants that are exposed to light with a plastic bag to prevent escape of co2 from soil.
one bell jar has soda lime to prevent entry of carbon dioxide and has a beaker of NaOH that absorbs carbon dioxide.
the other has a beaker of NaHCOthree to release carbon dioxide
to show that oxygen is given off during photosynthesis
the gas collected should re light a glowing splint.
see diagram with elodea
sodium hydrogen carbonate adds carbon dioxide necessary for photosynthesis
what does chlorphyll do?
chlorophyll transfers light energy into chemical energy in molecules for the synthesis of carbohydrates
where are most of the chloroplasts located?
most are located on the upper surface in the palisade cells. this means light can reach the chlorplasts easily as they only have to pass through the epidermis
use and storage of glucose
used by plant in respiration to provide energy
converted into other sugars such as sucrose
cellulose for new cells walls
amino acids -> proteins
fatty acids and glycerol for building lipids
transferred into vacuoles to form cell sap which supports the cell by turgor pressure
excess is stored as starch
what are nitrate ions used for?
making amino acids + protein
a deficency means the plant is not able to make protein which results in a slow, stunted growth, weak stem and yellow leaves
magnesium ions
used to make chlorophyll
deficency results yellowing leaves and in reduced rate of photosynthesis and stunted growth
what is a limiting factor?
something that when it is in short supply prevents a process from reaching its maximum rate
limiting factors for photosynthesis are:
light intensity
temp
carbon dioxide concentration
how would you investigate the effects of these factors on the rate of photosynthesis on elodea/ canadian pondweed?
- light intensity: use a lamp with dimmer/ place lamp away at certain distances from the plant
- carbon dioxide concentration: add increasing amoints of NaHCOthree
- temperature: water baths at different temps
why do you need to add NaHCOthree in experiments investigating the effects on photosynthesis?
to ensure carbon dioxide concentration does not become a limiting factor
why does osmosis occur at the root hair?
there is a higher water potential in the soul and a lower water potential in the root hair cell, as the root hair cell has a very concentrated cell sap. because of this, osmosis occurs and water moves from the soil to the root hair cells down a concentration gradient
what is the pathway for water movement in plants? but
the water travels across the cortex to the xylem tissue
the xylem vessels transport the water against gravity up from the roots through the stem to the leaves
the water leaves the xylem at the mesophyll layer in the leaves
transpiration pathway
water first evaporates from the spongy cells into the air spaces
the air spaves become full of water vapour
water vapour diffuses through the stomata into the air
the water lost from the spongy cells is replaced by more water frlm the xylem
mechanism of water uptake and movement
when water is lost from mesophyll cells they draw water out if the top of the xylem to replace the lost water. this causes tjere to be a lower water potential at the bottom than at the top, creatlng a tension at the top of the xylem that pulls water up the xylem.
a contious column of water is pulled up the xylem because the water molecules have high cohesive forces between them enabling them to stick together and be pulled uo
what is translocation?
translocation is the movement of sucrose and amino acids in phloem; from regions of production (sources) such as leaves or regions of storage (sinks) such as the storage tissue or the roots OR to regions where they are used in respiration or growth such as the flowers or growing tips of stem and roots
factors affecting transpiration
- temperature: increases kinetic energy of water molecules which causes an increase in the rate of evaporation of water from the leaf
- humidity: decreases diffusion gradient between leaf and atmosphere, so it decreases rate of transpiration
