why the 3 types of parenchmatous cells
are Specific names even though they similar in their origin?
Answers
Answer:
as their structures and functions are different, they must have to be given specific names based on their structures and functions.
Explanation:
Chlorenchyma: Cells which have chloroplast and perform photosynthesis
The mesophyll cells in leaves which differentiate into palisade and spongy cells
In the other green parts of the plants like stems, sepal etc.
Transfer Cells: They play an important role in the transport of solutes over short distances.
They have cell wall ingrowths, which greatly increase the surface area of the plasma membrane
Sucrose is transported across the membrane through a proton/sucrose co-transport mechanism
These are found in the areas of absorption and secretion in plants like nectaries, salt glands and in carnivorous plants
Vascular Parenchyma: The parenchyma cells which are associated with vascular tissues. These are of two types:
Phloem Parenchyma: It is made up of elongated, tapering and cylindrical cells having dense cytoplasm.
Plasmodesmata connections occur between the cells through pits in the walls
It stores food and other materials like resins, latex and mucilage
Absent in monocotyledons
Xylem Parenchyma: It is made up of thin-walled cells. The cell wall is made up of cellulose.
It stores food materials like starch, fats and other substances such as tannins and crystals
Radial conduction of water takes place by ray parenchymatous cells
In the water-stress condition, they help in preventing damage to tracheids and vessels
Storage Parenchyma: These store various substances like water, starch, proteins etc. They act as a food and water reservoir.
Stored protein is a good source of nitrogen for plants
In starch storing cells like in potato tubers, the endosperm of cereals and cotyledons, abundant starch-containing amyloplasts are present
Parenchyma cells may be specialised as a water storage tissue in succulent plants such as Cactaceae, aloe, agave, etc.
In the underground storage like in potato tuber, it can initiate the shoot growth and provide moisture for the initial growth of growing parts
Prosenchyma: These are fibre-like elongated cells, which are thick-walled and provide rigidity and strength to the plant
Aerenchyma: They contain very large intercellular spaces. These are present in aquatic plants.
Aerenchyma helps in the buoyancy of the floating plants
It helps in the respiration and provides sufficient oxygen to the aquatic plants
The aerenchyma formation takes place naturally in the roots of rice (Oryza sativa)
The aerenchyma of leaves and stems of aquatic plants are large longitudinal cells with air spaces or lacunae, which are gas-filled
Aerenchymatous cells are often water-filled
Aerenchyma cells are continuous from shoots to roots and help in diffusion of air from leaves to roots. It helps in maintaining sufficient oxygen levels for respiration.
The excess oxygen consumed, diffuses out from the roots into the soil atmosphere
They help in creating locally aerobic rhizosphere in the anaerobic soil
Epidermis Parenchyma: It is found in the epidermis of the leaves of some gymnosperms.
These have cutinised cell wall
No intercellular spaces
Cutin layer on the outer surface of epidermis reduces transpiration and counters the environmental stress
Have many spiny projections for the protection
Conjunctive Parenchyma: This type of parenchyma is present in the root system.
Non-cutinised, with the thin cell wall, present on the outer layer of the young parts of the root. It is known as epiblema or piliferous layer
It may form tubular outgrowths know as root hair
The main function is to absorb water and minerals from the soil
Functions of Parenchyma cells
Parenchyma cells form the ground tissue of plants. Parenchyma tissues perform various important functions: