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Morphology of Flowering Plants - Inflorescence

Grade 11CBSEBiology

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

🔑Concepts

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

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

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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).

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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).

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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.