What characteristic best describes parenchymal cells?

Parenchymal cells are best described as cubical and loosely packed due to their fundamental role in plant tissues. These cells are characterized by their thin cell walls and ability to divide and differentiate into various types of cells. Their loose packing provides ample space for air and intercellular substance, allowing for processes like gas exchange and storage of nutrients and water.

This structure makes them versatile, as they serve functions such as photosynthesis, storage of carbohydrates, and secretion. Their shape and arrangement enhance their ability to fulfill these essential roles in plant physiology. In contrast, other options present characteristics not typically associated with parenchymal cells; for instance, thickened or lignified walls are attributes of other cell types involved in structural support, not parenchyma, which emphasizes its multifunctional and supportive roles in plant biology.