•It’s a Biological Science. Other Biological Sciences include: Cell Biology, Histology, Microbiology, Biochemistry, Genetics, Molecular Biology, Anatomy, Botany, Zoology, and Physiology.INTRODUCTION
Plant Physiology is the science that studies the responsesof plants or parts of plants towards externalor internal agents or variables.
•Like any other science, its development started with the observation phase, then quantitative measurements are done and the knowledge gained is translated to more general cases.•The response of an organism is not exclusively conditioned by stimulus from the environment or by its nutrition. Great part of the response comes from the organism’s genetic makeup.
PHENOTYPE = GENOTYPE + ENVIRONMENT
•The main difference between animal and plant cell.•There is a close relationship between the structure of the cell wall and the function of the cell. •The cell wall functions as the skin and the skeleton of the plant.THE PLANT CELL WALL
The primary cell wall is the first to appear and is found in all young cells. In many cells, it’s the only cell wall that develops. Those cells that possess this cell wall only, are said to be in active growth.
A secondary cell wall develops when the cell stops growing. It develops from the internal surface of the primary cell wall and is much thicker than the primary with different composition and properties than the primary.
CHEMICAL COMPOSITIONTHE CELL WALL•The cell wall has a very complex structure and before understanding this structure, we need to first know its components.•Polysaccharidesare the most abundant component in all cell walls. These are sugars bonded together by glycosidic bonds.•There are three types of polysaccharides found in plant cell wall: cellulose, hemicellulose and pectin. Besides the polysaccharides, the cell wall also contains proteins, lipids, minerals. In later stages of development, cell walls can have great amounts of lignin.
The polysaccharides1.Cellulose.Cellulose is the most abundant component in plants. It is formed by long linear chains of glucose units in the form of crystalline aggregates, which give the wall a great part of its resistance. The level of polymerization (number of glucose molecules) that forms a molecule can vary from 8,000 –14,000. In primary cell walls the level of polymerization is shorter (2,500).
The polysaccharides2. Hemicellulose There are different classes of hemicellulose. All