tendril, slender, sensitive structure of many climbing plants that by a response to contact (see auxin) supports the plant. Tendrils are modified stems, leaves, or leaf parts or roots. Most young tendrils revolve slowly in their natural growth, as do the growing tips of roots and shoots; the tendrils of different plant varieties may have a consistent tendency to clockwise or to counterclockwise spiraling. The most common kind of tendril (pea, grape) coils around a slender support and then contracts spirally, becoming springy and drawing the plant to the support. The disk-tipped tendril (Virginia creeper, Boston ivy) adheres firmly to brick, stone, or wood, after which it too contracts. For other means of climbing in plants, see climbing plant.

Plant organ specialized to anchor and support vining stems. A tendril is a slender, whiplike or threadlike strand, produced usually from the node of a stem and composed of either stem or leafstalk tissue, by which a vine or other plant may climb. Sensitive to contact, the tendril turns toward any object it brushes against, wraps about it, and clings to it for as long as the stimulation persists. Later, strong mechanical tissue develops in the tendrils, making them strong enough to support the weight of the plant. Some tendrils have enlargements at the ends that flatten and produce an adhesive that firmly cements them to their support. Common examples of tendril plants are grape, English ivy, sweet pea, gourds, and passionflowers.

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