Tendril, a plant organ specializing in anchoring and protecting vine stems in botany. It is a specialized threadlike shaped stem, leaf, or petiole that is used by climbing plants for parasitic plants’ support, attachment, and cellular invasion, typically by twining around suitable hosts found by contact. The Humulus Lupulus, or the common hop, is an example of a plant which has tendrils. It is a climbing herbaceous vine that can grow very rapidly, and whose tendrils wrap in a clockwise direction around the support. Tendrils have no lamina or razor, but they are capable of photosynthesizing. They are susceptible to chemicals and can be shaped from modified shoots, modified leaves, or auxiliary branches, often deciding the direction of growth, as in the Cuscuta species.
A similar role is performed by other special plant structures, but the tendril is unique in being a specialized lateral organ that strongly has a twining propensity that causes it to encircle any objects encountered. Charles Darwin’s monograph On the Movements and Habits of Climbing Plants, originally published in 1865, was the earliest and most detailed study of tendrils. The term circumnutrition was also coined in this work to describe the motion of rising stems and tendrils seeking help. The phenomenon now known as tendril perversion, in which tendrils adopt the form of two parts of counter-twisted helices with a middle transition, was also observed by Darwin.
(Example of Tendril Plant Anatomy)
Tendrils start off in search of a surface to expand over by bending. When they find it a hormone called auxin will be released by the portion of the tendril that is in contact with the surface, which stimulates a wide region of the tendril that is not in touch with the surface to expand. It is only the terminal leaflets of the garden pea that are changed to become tendrils. The entire leaf is altered to become tendrils in other plants, such as the yellow vetch (Lathyrus aphaca), whereas the stipules are expanded and photosynthesized. Still, some, including members of the genus Clematis, use the rachis of a compound leaf as a tendril.
A tendril is a slender strand that is whiplike or threadlike, typically formed from the node of a stem through which a vine or other plant may ascend. Its anatomy may consist of stem tissue or tissue of the leafstalk. Grapes, members of the squash or melon family (Cucurbitaceae), sweet peas (Lathyrus odoratus), and passionflowers (Passiflora species) are common examples of tendril-producing plants. On the end of tendrils, the specialized pitcher traps of Nepenthes plants develop. In the center, the tendrils of aerial pitchers are normally coiled.
The hormone ethylene helps in growth in addition to auxin and regulates the shape of the cells. The overall process results in the cells contracting or growing slower when the support surface is touched, while those that do not touch it expand or grow faster. On different sides of the plant, the varying growth rates contribute to the coiling that occurs around the supporting component. It will normally curl around it if the tendril comes in contact with an object for a long enough time, creating a good anchor point for the pitcher. In this way, the tendrils help support the plant’s growing stem. Tendrils are driven by airborne chemicals from Cuscuta, a parasitic plant, and only twine around suitable hosts.
Later, in the tendrils, strong mechanical tissue (sclerenchyma) develops, thereby making them strong enough to support the plant’s weight. Continuous contact with the surface is required in order for a plant or plant organ to experience constant growth. While tendrils twine around hosts based on touch perception, plants have a form of self-discrimination and will avoid showing chemotropism based on chemoreception by twining around them.
In addition to their twining character, some tendrils create terminal enlargements that flatten and secrete an adhesive upon contact with a firm surface, securely cementing the tendril to the substrate. Finally remember that in order to react to contact, tendrils need light, so they can receive a stimulus in the dark and only respond until the light is visible.
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