Aestivation in Tomato and Onion

Introduction
Aestivation refers to the arrangement of sepals or petals in a flower bud. It is important for the protection of reproductive parts of the flower and for proper pollination. The term 'valvate' aestivation refers to the overlapping of sepals or petals in a unidirectional manner.

Aestivation in Tomato
In tomato flowers, the calyx has five sepals that are fused at the base. The sepals show valvate aestivation. In this arrangement, the sepals overlap each other with their margins without any particular direction. The sepals form a protective covering over the developing flower bud. As the flower bud matures, the sepals become dry and brittle and eventually fall off, exposing the petals.

Aestivation in Onion
In onion flowers, the perianth consists of six tepals that are fused at the base to form a tube-like structure. The tepals are arranged in two whorls of three each. The outer whorl shows valvate aestivation, while the inner whorl shows contorted aestivation. In valvate aestivation, the tepals overlap each other with their margins without any particular direction. In contorted aestivation, each tepal overlaps the adjacent one in both directions. This arrangement provides better protection to the reproductive parts of the flower.

Conclusion
Aestivation is an important factor in flower development, and it plays a crucial role in the protection of the reproductive parts of the flower. The arrangement of sepals or petals in a flower bud helps in proper pollination and eventually leads to the development of fruits and seeds. The valvate aestivation is the most common type of aestivation found in flowers.