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Plants (Plants (Attributes that are unique to plants (Cell wall made of…
Plants
Plants
Attributes that are unique to plants
Cell wall made of cellulose
Cell walls are permeable membranes that let everything through.
Their use is to support the structure of the cell
Chloroplasts - site of Photosynthesis. Plants use it to absorb light as there is chlorophyll in it.
Large permanent vacuoles
Vacuole keeps the shape of the cell.
Storage molecules
Store carbohydrates in the form
of starch
Water uptake into plants.
Plants require water for:
Photosynthesis:
Carbon dioxide + water = Glucose + Oxygen
Structural support:
plant cells want more water so they become
turgid and stronger
Transpiration:
Water vapour leaving the leaf
The entry point for water into the roots are
root hair cells.
Roots
Function of roots in plants
To support the structure of the plant:
stability
To make nutrients and water
Food storage
Asexual reproduction
Water transport in plants
Root hairs are single celled and
are adapted to their function of taking in water (there are also solutes mix in with the soil which travel with the water but the concentration of these solutes are still much less than the concentration of solutes inside the root hair cells) by having
a high surface area in comparison to having a low volume (single celled) which is good for diffusion. They also have:
They have a large vacuole
which can store minerals, ions and sugars. This means
their solubility is higher, lowering their water potential.
They also have a low water potential so osmosis can
happen easily mending more water can get into the plant quicker.
Long and thin.
After entering the root hair, the water travels through
neighbouring cells in the cortex to the xylem through osmosis (when water enters one cell in the cortex it gets a lower solubility level and higher water potential as there is more water in the cell. This means that osmosis can happen from one cell to another as the cells without the water have a low water potential. Eventually the water makes its way to the xylem.).
Water then travels up the xylem in the stem to the leaves where
photosynthesis can be conducted in the chloroplasts by a process in which water is pulled up in a continuous column known as the transpiration stream.
The continuous loss of water out of the
leaves through transpiration causes water to be pulled up the
xylem in the stem and the roots in a continuous flow. This is what is know as the transpiration stream. Functions of the transpiration stream include:
It supplies water for chloroplast in the leaf
to carry out photosynthesis and therefore respiration
It carries mineral ions dissolved in the water to other parts of the plant where they can be used to make a range of molecules such as amino acids and proteins
It provides water to all parts of the plant to keep
their cells turgid.
It is an important means of letting heat escape from the
plant. See school note book for more detailed info.
Transpiration and the way that water leaves the leaves.
Transportation is the evaporation
and loss of water vapour from the aerial
parts of a plant (like the leaves)
Factors affecting
rate of transpiration
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After entering the leaves from the xylem
the water travels through the leaf dropping of some of its self at different parts such as the chloroplast so it can conduct respiration.
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The xylem vessels are adapted to their function as they :
Lack a cytoplasm and a nucleus
meaning that there are is nothing in the way of the dissolved minerals and water meaning that it can travel very quickly and easily through the xylem . The only thing there is cell walls that prevent the xylem from collapsing in. The cell walls are thickened with cellulose and lignin.
The xylem has perforations in their side walls meaning that (see notes for image)
meaning the water is able to travel from one xylem to the next one to it if there was a blockage in one of the xylem.
There are no end walls or they are perforated (has wholes) this
that the water and mineral ions can travel easily.
The cellulose thickening in the xylem
is in a spiral or annular arrangement meaning that the xylem vessels can stretch during growth without collapsing.
The lignin that helps
make up the xylem cell walls are water proof helping
water travel easily and got getting soaked in by the cell walls
meaning not much water is wasted.
It is important to note that the xylem is dead
meaning that the water and mineral ions which have dissolved into the water don’t need to be used to keep the xylem alive meaning that the maximum amount of water and mineral ions can be transported.
Phloem transports sugars
and amino acids. Unlike the
xylem the phloem are alive.