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Leaf

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The node or nodal region of the culm will bear a leaf.

Fig. 17 - Leaf.

 

Leaves are borne alternately on the culm in opposite directions. One leaf is produced at each node. Varieties differ in the number of leaves produced.

Fig. 18 - Leaves alternate on the culm in opposite directions.

 

The topmost leaf below the panicle is the flag leaf. The flag leaf contributes largely to the filling of grains because it supplies photosynthetic products, mainly to the panicle.

Fig. 19 - Flag leaf.

 

The leaf sheath and leaf blade are continuous.

Fig. 20 - Leaf sheath and blade.

 

A circular collar joins the leaf blade and the leaf sheath.

Fig. 21 - Leaf collar.

 

The leaf sheath is wrapped around the culm above the node.

Fig. 22 - Leaf sheath and culm.

 

The swelling at the base of the leaf sheath, just above the node, is the sheath pulvinus. It is sometimes incorrectly referred to as the node.

Fig. 23 - Sheath pulvinus.

 

Leaf blades are generally flat. Varieties differ in blade length, width, thickness, area, shape, color, angle and pubescence.

Fig. 24 - Different varieties with varying blade characteristics.

 

With many parallel veins on the upper surface of the leaf, the underside of the leaf blade is smooth with a prominent ridge in the middle; the midrib.

 

Fig. 25 - Parallel veins on upper surface.

Fig. 26 - Leaf midrib.

Most leaves possess small, paired ear-like appendages on either side of the base of the blade. These appendages are called auricles. Auricles may not be present on older leaves. Another leaf appendage is the ligule, a papery membrane at the inside juncture between the leaf sheath and the blade. It can have either a smooth or hair-like surface. The length, color, and shape of the ligule differ according to variety.

Fig. 27 - Ligule and auricle.

 

Fig. 28 - Rice and grassy weed comparison

Although similar, rice seedlings are different from common grasses. While rice plants have both auricles and ligules, common grassy weeds found in rice fields normally do not have these features. These characteristics are often helpful in identifying weeds in rice fields when the plants are young.