Simple Tissue Cells Flashcards
(35 cards)
Name all the simple tissue cells
-Parenchyma, collenchyma, chlorenchyma and sclerenchyma
Describe the functions of the parenchyma cells (2)
-Although they are structurally unspecialized, they are metabolically active and are the main sites of vital activities
-Air spaces run from the external environment where they open as the stomata. These air spaces run in-between cells, allowing gaseous exchange to occur between the living cells and the external environment. Oxygen for photosynthesis and carbon dioxide for respiration can diffuse through the spaces. Occurs in the spongy mesophyll
Are the parenchyma food storages?
The parenchyma are food storages. Parenchyma cells are often the site of food storage within the storage organs, for instance, potato tuber has starch stored in the parenchyma cortex. A rare example is parenchyma cells storing food in thickened cell walls, for example hemicellulose of date seed endosperm
Other than gaseous exchange, food storage and metabolically active what else functions do parenchyma cells posses?
- The walls of the parenchyma cells are important pathways of water and mineral salt transport through the plant via the apoplast pathway. Substances can also move through the plasmodesmata between neighbouring cells.
What are the Chlorenchyma cells?
Chlorenchyma cells are parenchyma cells involved in photosynthesis, they have an abundance of chloroplast and the thinness of wall is advantageous for allowing light and carbon dioxide to pass through the chloroplast
What does the Collenchyma cells do?
-living cells modified to give support and mechanical strength. Mechanical tissue, providing support for the organs in which they are found.
Describe the structure of the collenchyma cell
Is characterized by the deposition of extra cellulose at the corners of the cells. The deposition occurs after the formation of the primary cell wall. Cells also elongate parallel to the longitudinal axis of the orgin.
What types is the collenchyma cells are most important for? and why?
Young plants, herbaceous plants and in organs where secondary growth does not occur. In these situations it is an important strengthening tissue supplementing the effects of the turgid parenchyma
What does the sclerenchyma cell do?
Assist in providing support and mechanical strength for the plant. The mature cells are dead and incapable of elongation so they do not mature until elongation of the living cells around them is complete
What are the two types of sclerenchyma cells?
Fibres and sclereids or stone cells
What does both the sclereids and fibres both have in common?
in the primary cell wall it is heavily thickened with depositions of lignin- a hard substance with great tensile and compressional strength. Deposition of lignin takes place in and on the primary cellulose cell wall as the walls thicken, the living contents of the cells are lost with the result that the mature cells are dead.
What does great tensile and compressional strength mean?
Great tensile- that it does not break easily on stretching, and a high compressional strength means that it does not buckle easily.
What are simple pits?
Both fibres and sclereids structures called simple pits appear in the walls ad they thicken. These represent areas where lignin is not deposited on the primary wall owing to the presence of groups of plasmodesmata
Describe the structure of fibres
Individual fibres are strong due to lignification of the walls, dead cells. They are long with pointed ends (tapered end walls). Long narrow dead cells at maturity with very thick walls. Found in outer regions of the cortex, pericycle of stems, xylem and phloem
Can collenchyma cells allow bending?
It is the first of the strengthening tissues to develop in the primary plant body and because it is living can grow and stretch without imposing limitations on the growth of other cells around it
What does the fibres do?
Provide structural support to older parts of the lant like stems and are essential in holding up large, heavy parts of the plant
Why is fibres important?
These cells make the plant rigid and strong, helping it withstand forces like wind or pressure from heavy fruits or flowers
What is the epidermis, is it living or dead and cell wall and shape
The epidermis causes protection from desiccation and infection. It is living, elongated and flattened with a single layer of cells covering the entire primary plant body
Role of the mesophyll, shape and location
Photosynthesis (contains chloroplast) and storage of starch. Found between the upper and lower epidermis leaves
Role of endodermis and location
Selective barrier to movement of water and mineral salt (between the cortex and xylem) in roots. Found around the vascualr tissue (innermost layer of the cortex)
What is the function of the pericycle and where it is found?
In roots, it retains meristematic activity, producing lateral roots and contributing to secondary growth if this occurs, found in roots between the central and vascular tissue and endodermis.
What is the function of Collenchyma, shape and function?
Support a mechanical function, elongated and polygonal with tapering ends. Outer regions of cortex eg angles of stems. midrib of leaves
Describe the sclereid cells
What are the two types of conducting cells
