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Morphology of Flowering Plants - Inflorescence

Grade 11CBSEBiology

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

Inflorescence is defined as the arrangement of flowers on the floral axis, also known as the pedunclepeduncle.

Based on whether the apex gets converted into a flower or continues to grow, inflorescences are classified into two major types: RacemoseRacemose and CymoseCymose.

In RacemoseRacemose type inflorescences, the main axis continues to grow (indeterminateindeterminate growth) and flowers are borne laterally in an acropetalacropetal succession (older flowers at the base, younger flowers at the tip).

In CymoseCymose type inflorescences, the main axis terminates in a flower, hence has limited growth (determinatedeterminate growth). Flowers are borne in a basipetalbasipetal order (older flowers at the top, younger flowers at the base).

Special types of inflorescence include CyathiumCyathium (found in EuphorbiaEuphorbia, looking like a single flower), VerticillasterVerticillaster (found in OcimumOcimum), and HypanthodiumHypanthodium (found in FicusFicus species like Fig and Banyan).

📐Formulae

Floral Symmetry:  (Actinomorphic), % (Zygomorphic)\text{Floral Symmetry: } \oplus \text{ (Actinomorphic), } \% \text{ (Zygomorphic)}

Floral Parts: K (Calyx), C (Corolla), P (Perianth), A (Androecium), G (Gynoecium)\text{Floral Parts: K (Calyx), C (Corolla), P (Perianth), A (Androecium), G (Gynoecium)}

Ovary Position: G (Superior), G (Inferior)\text{Ovary Position: } G_{\underline{\quad}} \text{ (Superior), } \overline{G} \text{ (Inferior)}

Cohesion/Adhesion: ( ) brackets denote fusion, CAˉ denotes epipetalous condition\text{Cohesion/Adhesion: ( ) brackets denote fusion, } \text{\={CA}} \text{ denotes epipetalous condition}

💡Examples

Problem 1:

Identify the type of inflorescence where the main axis ends in a flower and the flowers follow a basipetal arrangement. Provide an example.

Solution:

The inflorescence is CymoseCymose.

Explanation:

In CymoseCymose inflorescence, the growth of the main axis is terminated by the production of a flower. Subsequent flowers arise from lateral branches below. An example of this is the SolanumSolanum or Jasmine.

Problem 2:

Differentiate between the arrangement of flowers in Mustard and Radish compared to DianthusDianthus.

Solution:

Mustard and Radish exhibit RacemoseRacemose inflorescence, while DianthusDianthus exhibits CymoseCymose inflorescence.

Explanation:

In Mustard (BrassicaBrassica), flowers are produced in an acropetalacropetal succession on a continuously growing axis. In DianthusDianthus, the axis growth is limited and terminates in a flower, which is characteristic of the CymoseCymose pattern.

Inflorescence - Revision Notes & Key Diagrams | CBSE Class 11 Biology