Class 9 Biology Chapter 9 Notes
Important Notes of Transport Class 9 Biology Chapter 9 Notes written by Honorable Sir Adnan Haider Suib. These notes are very helpful in the preparation of Class 9 Biology Chapter 9 Notes for students of the 9th class Biology Urdu Medium and these are according to the paper patterns of all Punjab boards.
Summary and Contents:
Topics which are discussed in the notes are given below:
- Very Important Multiple Choice Questions (MCQs) of Chapter No.9 Transport Urdu Medium.
- TRANSPORT IN PLANTS: Water is vital to plant life. It is necessary not just for photosynthesis and turgor, but much of
the cellular activities occur in the presence of water molecules. Internal temperature of plant
body is also regulated by water. Land plants get water and minerals from soil. After absorption
by roots, water and minerals have to be transported to the aerial parts of body. Similarly food is
manufactured in leaves (by photosynthesis). This food is transported to other parts of body for
utilization and storage. All land plants (except mosses and liverworts), have developed complex vascular tissues (xylem
and phloem) that move water and food throughout plant body.
- Xylem tissue is responsible for the transport of water and dissolved substances from roots to
aerial parts. It consists of vessel elements and tracheids. Phloem tissue is responsible for the
conduction of dissolved organic matter (food) between different parts of plant body. It consists
of sieve tube cells and companion cells.
- Water always moves from an area of higher water potential to an area of lower water potential.
The relationship between the concentration of solute and water potential is inverse. When there
is a lot of solute ( i.e. hypertonic solution), the water potential is low and vice versa.
- WATER AND ION UPTAKE: In addition to anchor the plant, roots perform two other vital functions. First; they absorb water
and salts from soil. Second; they provide conducting tissues for distributing these substances to
the tissues of stem.
- The conducting tissues (xylem and phloem) of root are grouped in the centre to form a rod-shaped core. This rod extends throughout the length of root. Outside the conducting tissues, there
is a narrow layer of thin-walled cells, the pericycle.
- A single layer of cells i.e. endodermis surrounds this pericycle. External to this, there is a broad zone
of cortex. It consists of large and thin-walled cells. Cortex is bounded on outside by a single layer
of epidermal cells. Roots also have clusters of tiny root hairs, which are actually the extensions
of epidermal cells.
- TRANSPIRATION: Transpiration is the loss of water from plant surface through evaporation. This loss may occur
through stomata in leaves, through the cuticle present on leaf epidermis, and through special
openings called lenticels present in the stems of some plants.
- Most of the transpiration occurs through stomata and is called stomatal transpiration. The
mesophyll cells of leaf provide large surface area for the evaporation of water. Water is drawn from
xylem into mesophyll cells, from where it comes out and makes a water-film on the cell walls of
mesophyll. From here, water evaporates into the air spaces of the leaf. Water vapours then diffuse
from air spaces towards stomata and then pass to outside air.
- Opening and closing of
stomata: Most plants keep their
stomata open during the day
and close them at night. It is
the responsibility of stomata
to regulate transpiration via
the actions of guard cells.
The two guard cells of a
stoma are attached to each
other at their ends. The
inner concave sides of guard
cells that enclose a stoma
are thicker than the outer
convex sides. When guard
cells get water and become
turgid, their shapes are like
two beans and the stoma
between them opens. When
guard cells loose water and
become flaccid, their inner
sides touch each other and
stoma closes.