Plant cell is the basic unit of structure and function in nearly all plants. The range of specialization and the character of association of plant cells are very wide. In the simplest plant forms a single cell constitutes a whole organism and carries out all the life functions. In just slightly more complex forms, cells are associated structurally, but each cell appears to carry out the fundamental life functions, although certain ones may be specialized for participation in reproductive processes. In the most advanced plants, cells are associated in functionally specialized tissues, and associated tissues make up organs such as the leaves, stem, and root. Practically, every cell in the tissue of higher plants is a tiny, many-sided compartment enclosed by a water-impregnated wall otherwise composed principally of cellulose and other compounds closely related to carbohydrates. Plant cells vary greatly in size, shape and kinds. The development of a new cell, whether it arises by division or by fusion, involves its subsequent enlargement and maturation.
1. To study the structure of plant cell, its organelles and other inclusions. 2. To relate cellular structures with functions.
3. To compare the structure and components of cells from different plant parts.
Results and Discussion
Plants are multicellular organisms composed of millions of cells with specialized functions. At maturity, such specialized cells may differ greatly from one another in their structures. However, all plant cells have the same basic eukaryotic organization. Cells contain a nucleus, a cytoplasm and subcellular organelles and they are enclosed in a membrane that defines their boundaries.
In the Hydrilla leaf, observed under the microscope, Cells were so distinct that the outline and the rectangular shape of the cells were clearly seen.
Cell wall limits cell size. As the cells begin to enlarge, a thin primary cell wall composed of cellulose, which form the structural framework of the cell wall, hemicelluloses, and pectic compounds is constructed on each of the two sides of the middle lamella. Middle lamella cements the walls of two adjacent cells together. In the interior side of the cell wall reveals the presence of tiny green, spherical structures called chloroplasts. The Chloroplasts, visible under light microscope, are carried passively around the cell by the moving cytoplasm. The cytoplasm is in a fluid state. It is evidenced by the phenomena of streaming (also called cyclosis). The simplest manifestation of streaming consists of a rotation of the cytoplasm round the inner surface of cell wall. Cyclosis is accelerated by increases in temperature and stops in the absence of oxygen implying that the process of aerobic respiration is involved.
Cyclosis in a single cell
Looking at the center of the cell was the large central vacuole filled with cell sap enclosed with tonoplast which is not really visible under light microscope. Vacuole maintains the cell turgor, controls movement of molecules between the cytosol and sap, and stores useful materials and digests waste proteins and organelles.
In the onion bulb, cells from the onion peel were elongated and reddish in color. After the slide was stained with I2KI, the cytoplasm was lightly stained and the nucleus became very distinct showing its spherical body bounded by the nuclear envelope (black lining around the nucleus). Nucleus is the most prominent organelle. In the nucleus, there is a smaller circular structure called Nucleolus which manufactures protein-producing structures called ribosomes.
(stained with I2KI)
Plastids are usually centers of certain kinds of metabolic activity. Three kinds...