What are the functions of parenchyma tissues ?

Parenchyma are thin walled cells which pack the stem and help to support it. The  parenchyma between the epidermis and vascular tissue is called the cortex.
The parenchyma that lies withing the ring of vascular tissue os called the pith.
Turgor pressure within this tissue provides support to the stem

John H

parenchyma can store food
parenchyma can become air containing tissue providing bouyncy to float in aquatic plants .

Parenchyma cells are living cells that have diverse functions ranging from storage and support to photosynthesis and phloem loading (transfer cells).

Apart from the xylem and phloem in its vascular bundles, leaves are mainly composed of parenchyma cells.

Some parenchyma cells, as in the epidermis, are specialized for light penetration and focusing or regulation of gas exchange, but others are among the least specialized cells in plant tissue, and may remain totipotent, capable of dividing to produce new populations of undifferentiated cells, throughout their lives.

Parenchyma cells have thin, permeable primary walls enabling the transport of small molecules between them, and their cytoplasm is responsible for a wide range of biochemical functions such as nectar secretion, or the manufacture of secondary products that discourage herbivory.

Parenchyma cells which contain many chloroplasts and are concerned primarily with photosynthesis are called chlorenchyma cells.

Others, such as the majority of the parenchyma cells in potato tubers and the seed cotyledons  of legumes have a storage function.

KGR