[Biology Class Notes] on Tendril Pdf for Exam

It is a kind of plant organ that is used for anchoring and supporting the vining system. It can be a modified structure of leaves, leaflets, leaf tips, or leaf stipules. They may also be derived from modified stem branches like in grapes. They are thin, thread-like growths present on the stem or leaves of climbing plants. Based on growth tendril are of two types they are: stem tendril and leaf tendril. And their growth is mainly towards the support with which they can attach themself for the support and this phenomenon is known as thigmotropism.

 

Function of Tendril

Some of the common function of tendril are discussed below:

• They are known to be modified portions of leaf, stem or petiole. 

• Their main function is to provide support to the plant as it climbs up a structure. By doing so they allow a plant to find a more suitable area to grow due to more light.

• When stems are modified into tendril they help plants to climb. 

• The positions of tendril are different in different plants like in leaf, stem or even branches in few plants.

What is Stem Tendril?

When stems are modified into threadlike leafless structure then they are known as stem tendril. Their major role is for climbing purposes, they don’t necessarily contain a branch. 

 

Further Stem Tendril is classified into different types. They are as follows:

Axillary: E.g., Passiflora

 

Extra-Axillary: E.g., Luffa

 

Apical Bud: E.g., Grapevine

 

Floral Bud: E.g., Antigonon

 

What is Thigmotropism?

It is a kind of curvature movement shown by a plant in response to a unilateral touch stimulus and can be observed in many climbers. In tendril climbers, the tendrils first show mutation, and as soon as their apices touch support, they move thigmotropic ally to turn around it.

 

Some of the common examples of tendril-producing plants are the grape, members of the squash or melon family (Cucurbitaceae), the sweet pea (Lathyrus odoratus), and the passion flowers (Passiflora species).

 

Explain the Role of Auxin in the Growth of Tendril

It is a kind of growth hormone which is generally synthesized at the shoot tip. It enhances the growth of cells so that plants can increase their length. As soon as the tendril comes in contact with any support system, auxin stimulates the cell to grow faster on the opposite side that’s why the tendril forms a coil around the support.

 

Common Examples of Auxin based on their Synthesis

1. Naturally occurring auxins: Indole acetic acid, indole ethanol, indole acetaldehyde.

2. Synthetic auxins: Naphthalene acetic acid, indole butyric acid, 2, 4 – dichlorophenoxyacetic acid.

Tendrils

In Botany, tendrils are defined as the plant organ which is specialised for anchorage and supporting the vining stems. They can be defined as the modified leaves, leaf tips, leaflets or stipules. They can also be derived from modified stem branches like in grapes. Tendrils are distinct and are specialised structures which strongly possess a tendency to the leaf which then encircles any object it encounters. It is thus, slender and whip-like strand which is produced from the node of the stem which is a vine or plants that climb on objects or other plants. The anatomy of the tendrils may be like that of a leafstalk tissue or a stem tissue. Examples of plants having tendrils are grapes, melon family, squash family and peas. Tendrils are sensitive to contact and when it is bent towards the ground it actually bends towards the ground. When it encounters an object, it encircles the object and clings to it for a long time as long as the stimulation is persisted. Eventually, sclerenchyma which is a strong mechanical tissue develops in tendrils and supports the vining system which makes them strong enough to carry the weight of the plant.

Some of the tendrils produce terminal enlargements which come in contact with firm surfaces that flatten and secrete an adhesive which actually glues the tendril to the substrate. Based on the growth of the tendril, there are two types of them which are namely the stem tendril and leaf tendril.  The difference between the stem tendril and the modified tendril is that the stem tendril is a modified stem but the leaf tendril is a modified leaflet, leaf or its part. Both their growth mainly supports the part to which they are attached to and gives support to them. This process is called thigmotropism.