Class Notes
Class: X Subject: Biology
Topic: Ch- 6 Life processes[Transportation in Prepared by: Bharati Mandal
plants]
TRANSPORTATION IN ORGANISMS
All the organisms need to transport water, food, minerals, oxygen to different parts of
the body. They help in the growth and respiration of the cells. The waste products
are transported to the excretory organs for elimination from the body. Plants and
animals have different organs and processes for the transportation of substances.
These functions are performed by acirculatory system or transport system.
Transportation in plants
Plants have specialized vascular tissues for transportation of substances. There are
two types of vascular tissues in plants.
Xylem: Xylem is responsible for transportation of water and minerals.
It is composed of trachids, xylem vessels, xylem parenchyma and xylem fibre.
Tracheids and xylem vessels are the conducting elements.
The xylem makes a continuous tube in plants which runs from roots to stem
and right up to the veins of leaves.
It carries water and minerals from the roots to leaves of the plant.
Phloem: Phloem is responsible for transportation of food.
Phloem is composed of sieve tubes, companion cells, phloem parenchyma
and bast fibers.
Sieve tubes are the conducting elements in phloem.
Phloem carries product of photosynthesis from leaves to other parts of the
plant.
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Ascent of sap: The upward movement of water and minerals(collectively known as
‘sap’) from roots to different plant parts is called ascent of sap. Many factors play an
important role in ascent of sap and it takes place in many steps. They are as follows
:
Root pressure: The walls of cells of root hairs are very thin. Water from soil
enters the root hairs because of osmosis. Root pressure is responsible for
movement of water up to the base of th
e stem.
Capillary action: A very fine tube is called capillary. Water or any liquid rises
in the capillary because of physical forces and this phenomenon is called
capillary action. Water, in stem, rises up to some height because of capillary
action.
Adhesion-cohesion of water molecules: Water molecules make a
continuous column in the xylem because of forces of adhesion and cohesion
among the molecules.
Transpiration pull: Loss of water vapour through stomata and lenticels, in
plants, is called transpiration. Transpiration through stomata creates vacuum
which creates suction, called transpiration pull. The transpiration pull sucks
the water column from the xylem. tubes and thus, water is able to rise to
great heights in even the tallest plants.
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Transport of food: Transport of food in plants happens because of
utilization of energy. Thus, unlike the transport through xylem, it is a form of
active transport. Moreover, the flow of substances through phloem takes
place in both directions, i.e., it is a two-way traffic in phloem.
Transpiration is the process of loss of water as vapour from aerial parts of
the plant.
Note: The above content has been absolutely prepared from home.
Note: The above content has been absolutely prepared from home.
