question_answer 53)

  The mode of arrangement of sepals or petals in a floral bud is known as aestivation. Draw the various types of aestivation possible for a typical pentamerous flower.

Answer:

                  The mode of arrangement of petals or sepals in a flower bud with respect to the membersof the same whorl or with each other is known as aestivation. It is of following types Valvate Margin of adjacent petals or sepals touch each other, but do not overlap, e.g., mustard (Brasslca). Twisted Regular overlapping of petals or sepals occurs in which margin of one petal overlapwith the adjacent next one petal, e.g., China rose (Hibiscus rosasinensis). Imbricate There are five petals arranged in such a way that one petal is completely external and one petal is completely internal, three petals are partially external and partially internal, e.g., Cassia, Callistemon, Caesalpinia. Quincuncial There are five sepals or petals of which two are completely out and two arecompletely inside, while one is partially out and partially in e.g., Cucurbita (Cucurbitaceous). Vexillary It is the characteristic aestivation of corolla of family - Papilionaceae, in which corolla (petals) are papilionaceous. The largest overlap the two lateral petals (wings), which in turn overlap the two smallest anterior petals (keel) e.g., Artobotrys, Polyalthea, Pisum. (a)Valvate,                          (b)Twisted,                         (c) Imbricate,                     (d) Quincuncial and (e) Vexillary