Question

The term keel is used for special type of
A. Sepals
B. Petals
C. Stamens
D. Carpels

Answer 1

A keel is a structure of the papilionaceous type of flower. It is made up of two petals loosely united along their edges. Keel in flowers could be a term given to the 2 bottom petals present below the wings. Keels in flowers of the family Fabaceae. This is often so called because it's sometimes joined in such the simplest way to make a structure that resembles the keel of a ship.

Complete answer:
Let's discuss the option and find the correct answer.
A. Sepals: The outer parts of the flower which enclose a developing bud are called sepals . The sepal is a defensive organ. It encloses and protects the developing reproductive structures. The sepal opens when the flower blooms at maturity. Hence option A is incorrect.
B. Petals: A petal found in papilionaceous corolla is keel. Butterfly-like with one posterior standard is Papilionaceous type of corolla . It has two lateral wings, two inner and smaller keels. Hence option B is correct.
C. Stamens: The male reproductive part of a flower is called stamen. The stamen consists of a long slender stalk, the filament, with a two-lobed anther at the tip in all but a few extant angiosperms. Hence option C is incorrect.
D. Carpels: carpels are considered as the pistils of a flower. The female reproductive part of the flower is a carpel . It is interpreted as modified leaves which bear structures called ovules. Inside which the egg cells ultimately form and are composed of ovary, style and stigma. Hence option D is incorrect.

Hence option B: petals is the correct answer

Note: The petals differ in shape and size in the papilionaceous type of the corolla,. The posterior and the outermost petal is called the vexillum.The lateral petals are called the wings. The innermost anterior petals which are fused, it's called keel. Their aestivation is called descending imbricate or vexillary. In the family Fabaceae these are seen.