Which of the following is a key function of stems in plants?

Stems play a vital role in the overall structure and functioning of plants. They serve primarily as a support system, holding up the leaves, flowers, and fruits, enabling them to receive adequate sunlight and air, which is essential for photosynthesis. This supportive function allows the plant to grow upwards and spread out, maximizing its exposure to light.

Additionally, stems are crucial conduits for the transport of nutrients and water throughout the plant. They contain vascular tissues, specifically xylem and phloem, which allow for the movement of water, minerals, and sugars between the roots and the leaves. This transportation is essential for the plant's survival, as it sustains vital processes, including growth and metabolism.

While stems may provide a structure to support flowers and leaves, they do not produce food or absorb sunlight directly — these functions are primarily performed by the leaves through photosynthesis. Therefore, the key function of stems as a support structure and in the transport of nutrients clearly highlights their importance in the plant's lifecycle.