De-Duve and coworkers isolated in 1965 particles from liver cells and other tissues which were enriched with some other enzymes. Such as peroxidase, caltalase, glycolic acid oxidase and some other enzymes. The name peroxisom was applied because this organelle is specifically involved in the formation and decomposition of hydrogen peroxide in the cell.
These are single membrane enclosed cytoplasmic organelle found both in animal and plant cells. These are characterized by containing H2O2 – producing oxidases and catalase. They are approximately 0.5 µm in diameter. They have also been found in protozoa, yeast and many cell types of higher plants.
Glyoxysomes
Plants contain an organelle, which in addition to glycolic acid oxidase and catalase also possess a number of enzymes that are not found in animal cells. This organelle, called glyoxysomes are most abundant in plant seedlings, which rely upon stored fatty acids to provide them with the energy and material to begin the formation of a new plant. One of the primary activities in these germinating seedlings is the conversion of stored fatty acids to carbohydrates. This is achieved through a cycle, glyoxylate cycle, the enzymes of which are located in the glyoxysomes.
In plants, peroxisomes play important role in both catabolic and anabolic pathways. In seeds rich in lipids such as castor bean and soyabeans, glyoxysomes are the sites fro breakdown of fatty acids to succinate.
This organelle is present only during a short period in the germination of the lipid-rich seed and is absent in lipid-poor seed such as the pea.
Vacuoles
Although vacuoles are present both in animal and plant cells, they are particularly large and abundant in plat cells often occupying a major portion of the cell volume and forcing the remaining intracellular structures into a thin peripheral layer. These vacuoles are bounded by a single membrane and are formed by the coalescence of smaller vacuoles during the plant’s growth and development. Vacuoles serve to expand the plant cell without diluting its cytoplasm and also function as sites for the storage of water and cell products or metabolic intermediates.
The-plant vacuole is the major contributor to the turgor that provides support for the individual plant cell and contributes to the rigidity of the leaves and younger parts of the plants.