• Test corrections are available and will be due this
Friday, no exceptions.
• Quiz will be Friday
• Homework is due Friday
Plant Energy
• Green plants make their own food- using carbon dioxide,
water and minerals.
• Which are used to make carbohydrates, lipids, proteins and
• Where else are those molecules important?
• Photosynthesis is the fundamental process by which plants
manufacture carbohydrates from raw materials using energy
from light
How do plants get that energy?
• The simple action of sun shining on a plant won't give it
• Sunlight has to be trapped by chlorophyll (found in the
mesophyll cells).
• Once trapped, and absorbed, the energy will aid in carbon
dioxide combining with water (with the help of an enzyme
• This combination will make glucose, which stores the energy
from the sunlight.
How does the plant get the CO2 and H2O
Carbon Dioxide as a Source
• CO2 is obtained from the air
• though only 0.04% is available
• A leaf will stick out from the stem to expose its large surface
area, and thereby obtaining as much CO 2 as possible
• How does water enter the
• Through which transport?
Water as a Source
• Water is taken up via osmosis through the root hair cells
• The water is carried by the xylem to all part of the plant, as if the
plant was sucking through a straw
• The water moves from the roots to the top of the plant through
• Transpiration is the evaporation of water at the surfaces of the
mesophyll cells followed by the loss of water vapor from plant
leaves, through the stomata.
• Meaning as water is lost transpiration producing a tension (pull)
from above, creating a water potential gradient in the xylem,
drawing cohesive water molecules up the plant .
Layers in a Plant Cell
Label and State the importance of the cells
Vascular Bundle Sheath
Xylem Vessels
Phloem Tubes
• Carries water and minerals
• Like a drainpipe, it is made
up of hallow dead cells
joined end to end
• runs from the roots of the
plant up through the stem
and branches out into every
• Has no cytoplasm or nuclei
• Its walls are made up of
lignin which is strong enough
to keep plants upright
• Carry organic nutrients which
the plant has made
• Many cells joined together
while still having their end
walls, thus forming sieve plates
(have small holes throughout)
• Sieve tubes have cytoplasm,
but does not have a nucleus or
• Sieve tubes have a companion
cells that has a nucleus and
provides resources
• In a root the vascular bundle is found in the center
• In the stem, the vascular bundle is arranged in a ring near the
outside edge.
• Organic food materials made by the plant, like sugar, is transported
via the phloem.
• It is carried from the leaves to whichever part of the plant needs it
through translocation.
• Translocation is the movement of sucrose and amino acids in
phloem, from regions of production to regions of storage, or
regions of use for respiration or growth.
Plants also need minerals
When Variations Occur
• Transpiration is a special example of evaporation so any factor that
affect evaporation will also affect transpiration.
1. Temperature: the higher the temperature the faster the rate of
2. Humidity: the lower the humidity the faster the rate of
3. Light: stomata open in light for photosynthesis and so
transpiration will be high; they close when it is dark and so
transpiration is greatly reduced.
4. Water Supply: if plant is short of water, stomata close reducing
transpiration and so conserve water.
Water Vapor Loss
• Water moves out of the mesophyll cells forming a film of moisture
over their surfaces
• Water evaporation occurs from this film, and this vapor gathers in
the large air spaces.
• Water vapor will then diffuses through the stomata to the drier air
outside the leaf.
• When soil lacks mineral ions fertilizers are added
• Fertilizers are chemical compounds rich in the mineral ions
needed by the plants, helping them grow faster, increase in
size and become greener
• Disadvantages:
• Excess minerals and chemical can enter a nearby river
polluting it
• This creates a layer of green algae on the surface, causing a
lack of light in the river, thus preventing the aqua plants