For BIO Students

1. Transport
In Flowering Plants
Biology
By: M.Wali Afridi

2. Transport in Flowering Plants:
What is transported?
● Water
● Minerals/salts
● Carbohydrate(glucose)
● Gases(CO2, O2)
Structures that carry out transport:
● Xylem
● Phloem
● Roots
Plants have two transport systems: xylem and phloem
● The xylem vessels carry water and minerals from the roots to the leaves and helps to support the
plant.
● The phloem tubes carries manufactured food from the leaves to the other parts of the plant.

4. Xylem Vessels:
Xylem tissue is composed of many hollow, dead cells
joined end to end to form long empty tubes. A long open
tube is formed because the end walls of the cell have
disappeared.
● Xylem vessels contain no cytoplasm or nuclei.
● Their walls are made of cellulose and lignin.
● Lignin is very strong and this is how the xylem
vessels help to keep plants upright.
● Xylem vessels run from the root of the plant,right up
through the stem and branch out into every leaf.

5. Phloem Vessels:
Phloem tissue is composed of sieve tube cells, which
form long columns with holes in their end walls called
sieve plates. This is due to their end walls not being
completely broken down.
● Sieve tube elements contain cytoplasm, but no
nucleus or lignin in their walls.
● Each sieve tube has a companion cell next to it.
The companion cell has a nucleus and contains
many other organelles.
● These companion cells are connected to the sieve
tube cells by plasmodesmata, and provide them
with proteins, ATP and other nutrients.

6. Vascular Bundles:
A vascular bundle is a group of xylem vessels and
phloem tubes. Xylem vessels and phloem tubes are
usually found close together. They help to support the
plant.
Vascular Bundles In Roots:
● In a root,vascular tissue is found at the centre.
Vascular Bundles In Stems:
● In a stem the vascular bundles are arranged in a
ring near the outside edge.

8. The Transport of Water:
● Xylem vessels carry water to all parts of the plant.
● Plants take in water from the soil through their root hairs.
● Water moves up xylem vessels because the pressure at
the top of the vessels are lowered, while the pressure at
the bottom stays high.
● This happens because of transpiration.
● Root hairs absorb water and minerals by the process of
osmosis from the soil.
● Root hairs are on the edge of a root and the xylem vessels
are in the centre.
● The water absorbed by the root hairs travel by osmosis
through the cortex, from cell to cell. eg. of movement of
water through plant.
Water move up xylem vessels?
Xylem vessels are very narrow and the
attraction of water molecules to those of
the cell wall by cohesion adhesion is
great. This helps to keep the continuous
flow of water from the roots to the
leaves.

9. Transpiration:
● Transpiration is the evaporation of water from a plant.
This evaporation occurs mostly from the leaves through
the stomata.
● Stomata are tiny pores found in the epidermis on a leaf
or stem, used for gas exchange. (eg. of stomata)
● Water is constantly being taken from the top of the
xylem vessels to supply the cells in the leaves. This
reduces the effective pressure at the top of the xylem
vessels, so that water flows up them. This process is
known as the transpiration.
Conditions that affect Transpiration rate:
● Temperature: transpiration increases as temperature
increases.
● Humidity: transpiration decreases as humidity
decreases.
● Wind speed: transpiration
increases as wind speed
increases.
● Light intensity: transpiration
increases as the light intensity
increases.
● Water supply: transpiration
decreases when water supply
decreases below a certain level.

10. Uptake of Mineral Salts:
Root hairs absorb mineral salts against their
concentration gradient. Special carrier molecules in the
cell membrane of the root hair carry the mineral ions
across the cell membrane into the cell,against their
concentration gradient. This is called active transport.
This process uses a lot of energy which is supplied by
the mitochondria in the root hairs.
Transport of Manufactured Food:
The phloem translocates organic foods,especially sugar
that the plant produces. Translocation is the process in
which manufactured food is transported from where
they are produced(leaves) to the part of the plant where
it is needed.
That’s All Thank you!