Flower is the modified and condensed shoot that helps in sexual reproduction.
Flower is the modified and condensed shoot that helps in sexual reproduction. An angiospermic flower shows a thalamus on which the floral leaves are arranged. In a typical angiospermic flower floral leaves are arranged in four distinct whorls. They are 1. Calyx (sepals), 2. Corolla (petals), 3. Anedroecium (stamens), and 4. Gynoecuim (carpels). As the Calyx and corolla do not directly take part in reproduction they are called on essential organs (also called perianth). Androecium and Gynoecuim take part in reproduction hence called essential organs.
The bract side of a flower is called anterior side and axis side is called posterior side. If a flower has bract it is called bracteates and if bract is absent it is ebracteate. If a flower has pedicel (stalk), it is called pedicellate, if pedicel is absent it is sessile. Sometimes small leaf like bracteoles may be present on the pedicel. Then the flower is described as bracteolate, if bracteoles are absent it is ebracteolate.
Key concepts about Flower:
1. Based on the sexuality of flowersthey may be Monoecious (Cocos), Dioecious
(Vallisnaria) or Polygamous (Mangifera).
2. Based on the arrangement of floral parts the symmetry of the flower may be
spiral or Acyclic (Mangnolia), Hemicyclic (Annona) or Cyclic (Hibiscus).
3. Based on the structural symmetrythe flowers are classified into Actinomorphic
flower (Hibiscus), Zygomorphic flower (Dolicus) and Asymmetric flower (Canna indica)
4. Based on the number of floral parts in each whorl (merosity), the flowers may be
Trimerous, (Allium), Tetramerous (Brassica) and Pentamerous (Hibiscus).
5. Based on the position of Gynoecium on the thalamus the flowers may be
Hypogyous (Hibiscus), Perigynous (Tephrosia) and Epigynous (Tridax).
6. The mode of arrangement of perianth loves in bud condition is called
‘Aestivation’. It may be Valvate (Calyx of Hibiscus), Twisted (Corolla of Datura), Ascendingly imbricate (Corolla of Caesalpiniaceae), Descendingly imbricate (Corolla of Fabaceae) and Quicuncial (Calyx of Ipomoea).
7. In the stamens the filament is attached to the anther in different ways like
Basifixed (Datura), Adnate (Nelumbo), Dorsifixed (Hibiscus), Versatile (Oryza).
8. The union of stamens is of two types. A. cohesion B. Adhesion.
9. the fusion among the stamens themselves is called cohension. It may be Adelphy
( the filament are united while the anthers are free Ex: Hibiscus), Syngenecious (the anthers are fused but the filament are free Ex: Tridax) and Synandrous (both the filaments ad anthers are united Ex: Cucurbita).
10. Depending on the number of carpels in the Gyoecuim, the gynoecium
maybe Monocarpellary (Dolichus), Bicarpellary (Solanum), Tricarpellary (Allium), Tetra carpellary (Oenother), Penta carpellary (Hibiscus) and Multicarpellary (Abutions).
11. Based o the number of locules in the ovary the ovary may be Unilocular
(Dolichus), Bilocular (Solanum), Trilocular (Allium), Tetra locular (Ipomoea), pentalocular (Hibiscus), and Multilocular (Aution).
12. The mode of arrangement of ovules in the ovary on the placenta is called
‘Placentation’. It may be Marginal (Dolichus), Parietal (Cucurbita), Axile (Hibiscus), Free central (Dianthus) , Basal (Tridax) and Superficial (Nymphaea).