What parenchyma does
Four jobs, and the tissue is the same in all four. What changes is where it sits and what it happens to be full of.
Photosynthesis
The palisade and spongy parenchyma of a leaf contain chloroplasts, so photosynthesis takes place inside them. Parenchyma with chloroplasts is where a plant makes its food.
Storing food
Some parenchyma stores food, and is then called storage tissue. The potato tuber, sweet potato and carrot roots, and papaya and banana fruits are all examples.
Storing water
Especially in xerophytes — plants of dry places. Aloe leaves, akkapana leaves and the cactus stem all store water in parenchyma.
Providing support
In herbaceous plants such as kudalu, the vacuoles of the parenchyma cells fill with water and the turgidity that results supports the plant.
Support without any hard tissue at all
The fourth function is the surprising one. A soft plant stands upright not because anything in it is stiff, but because every cell is swollen tight with water and pressing on its neighbours — the way a row of inflated balloons packed in a box holds its shape. Water is doing the work, and the parenchyma is only the container.
Which is why a plant wilts
Take the water away and the vacuoles shrink, the cells stop pressing on one another, and the whole plant droops. Nothing has broken and nothing has been lost — the support was never in the structure, only in the pressure. Water it and the plant stands up again.
One tissue, four jobs
Parenchyma carries out photosynthesis, stores food, stores water, and supports soft plants by turgidity. The last is why an unwatered plant wilts and a watered one recovers.