What parenchyma is

The most abundant tissue in a plant, and the least specialised. If you slice a plant anywhere and find large pale cells filling the space, that is parenchyma.

Parenchyma

The tissue that makes up the soft parts of the plant body is called parenchyma. It is the tissue found most abundantly in a plant.

Figure to be added

Figure 1.7 — parenchyma tissue in two views: a cross-section showing rounded cells with thin walls, small gaps where three cells meet, and the nucleus pressed against the wall of each cell; and a longitudinal section showing the same cells from the side.

The characteristics

They are living cells.
They are spherical, or isodiametric — about as wide as they are long — with a large central vacuole.
The nucleus lies at the edge of the cell, pressed against the wall by the vacuole.
There is a very thin cell wall, and it is made of cellulose.
There are intercellular spaces between the cells.

Nearly the opposite of a meristematic cell

Large where the meristematic cell was small; a big vacuole where it had none; a nucleus at the edge where it had a nucleus filling the middle; gaps between the cells where it had none. Every difference is the difference between a cell that is dividing and a cell that has stopped and grown.

The least specialised tissue does the most different jobs

A thin wall, a big vacuole and room to spare are not adaptations to one task. They are what a general-purpose plant cell looks like — which is why parenchyma turns out to do storage, photosynthesis and support, and why it is the tissue the other two simple tissues are modifications of.