PLANT CELLS AND TRANSPORTATION
PLANT CELLS:
Cells are the structural and functional
units of all living organisms. The study
of the structure and function of the cell is
called Cytology or Cell biology.
A plant cell is typically rectangular or cube shaped. It has an outer covering called cell wall which protects and gives it shape. A cell membrane, also known as the plasma membrane, surrounds the cytoplasm and its organelles. The plasma membrane, cytoplasm and the nucleus together are referred to as the protoplast. The cytoplasm carries various cell organelles like endoplasmic reticulum, mitochondria, chloroplast, Golgi bodies and ribosomes.
Groups of cells having a common origin and performing similar functions are called tissues.
A plant cell is typically rectangular or cube shaped. It has an outer covering called cell wall which protects and gives it shape. A cell membrane, also known as the plasma membrane, surrounds the cytoplasm and its organelles. The plasma membrane, cytoplasm and the nucleus together are referred to as the protoplast. The cytoplasm carries various cell organelles like endoplasmic reticulum, mitochondria, chloroplast, Golgi bodies and ribosomes.
Groups of cells having a common origin and performing similar functions are called tissues.
TRANSPORTATION:
The uptake and release of air, water,
solutes and sap in plants involves
transportation. It is a life process by which
a substance, absorbed or made in one part
of the body of an organism, is carried to
the other parts of the body.
Due to the branching shape of a plant,
all the cells of a plant can get oxygen
for respiration and carbon-dioxide for
photosynthesis directly from the air by
diffusion.
Therefore the transport system primarily
involves transport of water, minerals and
food prepared in the leaves to the various parts of the plant.This is done through two
specialized transport systems made of
xylem and phloem cells.
The transport of materials in a plant can be divided into two parts:
i) Transport of water and minerals in the plant.
ii) Transport of food and other substances like hormones in the plant.
Transport of Water and Minerals:
Water and minerals are absorbed
from the soil by the roots of the plant and
transported to the various parts of the plant
like stem, leaves and flowers. Water, along
with the minerals dissolved in it, moves
from the roots to the other parts through
the two kinds of xylem cells called xylem
vessels and tracheids. The transport of materials in a plant can be divided into two parts:
i) Transport of water and minerals in the plant.
ii) Transport of food and other substances like hormones in the plant.
Transport of Water and Minerals:
In pteridophytes and gymnosperms, tracheids are the only water conducting tissues.
In angiosperms either xylem vessels or both xylem vessels and tracheids transport water.
The movement of water and dissolved salts in the xylem is always upwards and it is caused by the suction of water at the top because of the low pressure created by transpiration from leaves.
Transport of Food and Other Substances:
The transport of food from leaves to the other parts of the plant is called translocation. The movement of food materials through phloem depends on the action of living cells called sieve tubes. Food is made in the mesophyll cells of a leaf. This enters into the sieve tubes of the phloem and is transported to all other parts of the plant body by the network of sieve tubes present inside the stem and roots.
The movement of food in phloem can be upwards or downwards or lateral depending upon the needs of the plant.
