Short essay on the Stipules of Leaf

Stipules are the appendages or outgrowths from the leaf base. It protects the young axillaries buds. Leaf is said to be stipulate when the stipule is present, while in its absence the leaf is estipulate.

Stipules are very common in dicotyledons but rare in monocotyledons. In some leaves they remain as long as the lamina persists (persistent or fall off soon after the lamina unfolds (deciduous). Stipules may remain as a not appendage or may be modified to give different structures.

According to their shape, position and size, stipules are of following types

A. Normal stipules:

(i) Free-lateral:

These are two in number, free, laterally placed at the leaf base and green in color e.g., China rose.

(ii) Adnate:

In this case, two lateral stipules grow along the petiole up to a certain height forming two winged appearance, e.g., Rosa.

(iii) Interpetiolar:

This type of stipule is seen in plants having opposite leaves. The stipules lie between the petioles of opposite leaves, alternating with the latter, e.g., lxora.

(iv) Intrapetiolar:

In this case, stipules present at the base of the opposite leaves, each being at the axil of a leaf, e.g., Ervatamia and Gardenia.

(v) Ochreate:

It forms a hollow tube like structure encircling the inter node of the stem up to a certain height along with the some part of the petiole. The stipule is membranous, e.g., Polygonum.

B. Modified stipules:

(i) Foliaceous:

At the base of the rachis of a compound leaf, there are two large, green, leafy structures known as foliaceous stiplue, e.g., Pisum.

(Ii) Bud-scales or convolute:

These are two scaly stipules present on the two lateral sides of the leaf bases enclosing the bud and becoming convolute in shape. When the leaves unfold, these scaly stipules fall off, e.g., Ficus, Artocarpus, and Magnolia, etc.

(iii) Spinous:

In this case, the stipules appear as two sharp pointed strucutres that provide

Protection to the plant, e.g., Acacia, Mimosa, Zizyphus.

(iv) Tendrillar:

The stipules develop on two sides of the petiole and become thin, wiry, coil like structures helping the plant to climb;, e.g., Smilax.

(v) Stipe:

Sometimes in compound leaf the outgrowths are found at base of the leaflets.

These are known as stipels, e.g., Clitoria, Dolichos lablab,