Plant Cells

Most cells are not visible with the naked eye. However, with microscopes of various types, plant cells can be readily viewed and studied. In young parts of plant and fruits, cell shapes are generally round, while in older sections, the cells are somewhat boxlike with up to 14 sides as they become packed together.

A plant cell is bounded by a cell wall and the living portion of the cell is within the walls and is divided into two portions: the nucleus, or central control center; and the cytoplasm, a fluid in which membrane-bound organelles are found. Between the primary cell walls of adjacent plant cells, lies a pectic middle lamella. There can be a secondary cell wall that would be located just to the inside of the primary wall. Both walls consist mainly of cellulose, but the secondary cell wall may contain lignin and other substances. The outer boundary of the protoplasm (cytoplasm and nucleus) is a sandwich-like, flexible plasma membrane. This membrane regulates what enters and leaves the plant cell. Plant cell organelles include: endoplasmic reticulum, with and without ribosomes attached; Golgi bodies, mitochondria, and plastids. Plastids are chloroplasts, chromoplasts or leucoplasts—depending on the color and likewise the function. Chloroplasts are of specific interest to those studying plants. A plant cell also, obviously, contains a nucleus which is bounded by a nuclear envelope with pores. The pores in the nuclear envelope allow for the movement of substances in and out of the nucleus. Within the nucleus is a number of chromosomes. The number present is specific to the organism and it will be later noted how sex cells contain one-half the number of chromosomes and restore chromosome number upon fertilization. All of these organelles and the nucleus are suspended in the cytoplasm. The cytoplasm has movements that are referred to as cytoplasmic streaming or cyclosis. The particular function of the other organelles contained in plant cells can be reviewed below: