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Tapetum (botany)

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– **Types of Tapetum**:
– Two main tapetum types are recognized: secretory (glandular) and plasmodial (amoeboid).
– In the secretory type, a layer of tapetal cells remains around the anther locule.
– In the plasmodial type, tapetal cell walls dissolve and their protoplasts fuse to form a multinucleate plasmodium.
– A less common type, the invasive non-syncytial tapetum, has been described in Canna.
– In monocots, Acorales have a secretory tapetum while Alismatales are predominantly plasmodial.

– **Functions of Tapetum**:
– Tapetum is crucial for the nutrition and development of pollen grains.
– It serves as a source of precursors for the pollen coat.
– Tapetum helps in pollen wall formation and transportation of nutrients to the inner side of the anther.
– It synthesizes callase enzyme for the separation of microspore tetrads.
– The tapetum cells usually have more than one nucleus per cell.

– **Processes in Tapetum**:
– Endomitosis is a process involved in tapetum function.
– Normal mitosis not followed by cytokinesis occurs in tapetal cells.
– Formation of restitution nuclei is part of tapetum processes.
– Endoreduplication is a process observed in tapetal cells.
Polyploidy and polyteny can sometimes be seen in tapetum cells.

– **Research and Studies**:
– Polowick and Sawhney (1993) studied the differentiation of tapetum during microsporogenesis in tomato.
– Furness & Rudall (2001) published research on the tapetal cell wall in plants.
– Further studies are needed to explore the detailed functions and mechanisms of tapetum.
– Understanding tapetum is essential for advancements in plant reproductive biology.
– Research on tapetum contributes to improving crop yields and plant breeding techniques.

– **Importance of Tapetum**:
– Tapetum provides nutrients and regulatory molecules to developing pollen grains.
– It plays a vital role in the reproductive process of flowering plants.
– The specialized functions of tapetum contribute to successful pollination and fertilization.
– Knowledge of tapetum is essential for plant genetic engineering and hybridization.
– Understanding tapetum can lead to innovations in agriculture and horticulture.

Tapetum (botany) (Wikipedia)

The tapetum is a specialised layer of nutritive cells found within the anther, of flowering plants, where it is located between the sporangenous tissue and the anther wall. Tapetum is important for the nutrition and development of pollen grains, as well as a source of precursors for the pollen coat. The cells are usually bigger and normally have more than one nucleus per cell. As the sporogenous cells undergo mitosis, the nuclei of tapetal cells also divide. Sometimes, this mitosis is not normal due to which many cells of mature tapetum become multinucleate. Sometimes polyploidy and polyteny can also be seen. The unusually large nuclear constitution of the tapetum helps it in providing nutrients and regulatory molecules to the forming pollen grains. The following processes are responsible for this:

  • Endomitosis
  • Normal mitosis not followed by cytokinesis
  • Formation of restitution nuclei
  • Endoreduplication
Schematic of anther ( 1: Filament 2: Theca 3: Connective 4: Pollen sac or Microsporangium)
Section of anther, showing dehiscence and release of pollen (1: Vascular bundle 2: Epidermis 3: Fibrous layer 4: Tapetum 5: Pollen

Tapetum helps in pollenwall formation, transportation of nutrients to inner side of anther, synthesis of callase enzyme for separation of microspore tetrads.

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