Which structure serves primarily for the support of climbing plants?

Tendrils are specialized structures that play a crucial role in the support of climbing plants. They are typically slender, thread-like appendages that can coil around nearby objects, providing stability and helping the plant to anchor itself as it grows upwards or sideways. This climbing adaptation allows the plant to reach sunlight more effectively, which is essential for photosynthesis and overall growth.

In contrast, stolons, rhizomes, and tubers serve different purposes. Stolons, also known as runners, are horizontal stems that grow along the ground, allowing the plant to propagate vegetatively. They are not primarily for climbing support. Rhizomes are underground stems that serve to store nutrients and allow for asexual reproduction by producing new shoots and roots. Tubers are swollen structures that store food, which can provide energy for the plant but do not offer climbing support. For these reasons, tendrils are the correct answer, as they are specifically adapted to assist climbing plants in their growth strategy.