TRANSPORT IN PLANTS
(a) The need for transport systems in multicellular plants.
● To include an appreciation of size, metabolic rate and surface area to volume
ratio (SA:V).
Need for a transport system
There are three reasons why plants need a transport system. Firstly, the cells of green
plants make their own glucose by photosynthesis, but much of the plant does not and
they need oxygen and glucose transported to the, and the waste products of cell
metabolism removed. Additionally, plants continue to grow their entire lives and they
can grow to enormous sizes which means they need transport system to survive the
great size that they have. As they increase in size, their surface area to volume ratio
decreases so they cannot just rely on diffusion alone.
(b) (i) The structure and function of the vascular system in the roots, stems and
leaves of herbaceous dicotyledonous plants.
● Xylem and Phloem in the root: a vascular bundle is found at the centre of a
young root. There is a central core of the xylem, often in the shape of an X, or
star-shaped. The phloem is found between the arms of the X-shaped xylem
tissue. The arrangement provides strength to withstand the pulling forces to
which roots are exposed.
○ Around the vascular bundle is a sheath of cells called the endodermis.
The endodermis has a key role in getting water into the xylem vessel,
and just inside the endodermis is a layer of meristem cells called the
pericycle.
● Xylem and Phloem in the Stem: The vascular bundles are found near the outer-
edge of the stem. In non-woody plants, the bundles are separate and discrete,
In woody plants, the bundles are separate in young stems, but became a
continuous ring in older stems. This means there is a complete ring of vascular
tissue just under the bark of the tree. This arrangement provides strength and
flexibility to withstand the bending forces which stems and branches are
exposed to.
○ The xylem is found towards the inside of each vascular bundle and the
phloem towards the outside. In between the xylem and the phloem is a
layer of cambium. The cambium is a layer of meristem cells that divide
to produce new xylem and phloem.
● Xylem and Phloem in the Leaf: The vascular bundles form the midrib and the
veins of the leaf. A dicotyledonous lead has a branching network of veins that
get smaller as they spread away from the midrib. Within each vein, the xylem is
located on top of the phloem.
(a) The need for transport systems in multicellular plants.
● To include an appreciation of size, metabolic rate and surface area to volume
ratio (SA:V).
Need for a transport system
There are three reasons why plants need a transport system. Firstly, the cells of green
plants make their own glucose by photosynthesis, but much of the plant does not and
they need oxygen and glucose transported to the, and the waste products of cell
metabolism removed. Additionally, plants continue to grow their entire lives and they
can grow to enormous sizes which means they need transport system to survive the
great size that they have. As they increase in size, their surface area to volume ratio
decreases so they cannot just rely on diffusion alone.
(b) (i) The structure and function of the vascular system in the roots, stems and
leaves of herbaceous dicotyledonous plants.
● Xylem and Phloem in the root: a vascular bundle is found at the centre of a
young root. There is a central core of the xylem, often in the shape of an X, or
star-shaped. The phloem is found between the arms of the X-shaped xylem
tissue. The arrangement provides strength to withstand the pulling forces to
which roots are exposed.
○ Around the vascular bundle is a sheath of cells called the endodermis.
The endodermis has a key role in getting water into the xylem vessel,
and just inside the endodermis is a layer of meristem cells called the
pericycle.
● Xylem and Phloem in the Stem: The vascular bundles are found near the outer-
edge of the stem. In non-woody plants, the bundles are separate and discrete,
In woody plants, the bundles are separate in young stems, but became a
continuous ring in older stems. This means there is a complete ring of vascular
tissue just under the bark of the tree. This arrangement provides strength and
flexibility to withstand the bending forces which stems and branches are
exposed to.
○ The xylem is found towards the inside of each vascular bundle and the
phloem towards the outside. In between the xylem and the phloem is a
layer of cambium. The cambium is a layer of meristem cells that divide
to produce new xylem and phloem.
● Xylem and Phloem in the Leaf: The vascular bundles form the midrib and the
veins of the leaf. A dicotyledonous lead has a branching network of veins that
get smaller as they spread away from the midrib. Within each vein, the xylem is
located on top of the phloem.
