The Necrohormone theory explains how dying cells can trigger the development of new embryos in certain plants.
Understanding the Necrohormone Theory
This theory, proposed by Haberlandt, focuses on the role of degenerating cells in initiating the formation of adventive embryos. Here's a breakdown:
- Degenerating Cells: The theory starts with cells that are in the process of dying, specifically those in the nucellus, a tissue within the ovule of a plant.
- Stimulus for Division: According to the theory, as these nucellus cells degenerate, they release a stimulus (the "necrohormone").
- Adventive Embryo Formation: This stimulus then prompts the adjacent living cells to divide and develop into adventive embryos. These are embryos that develop outside the usual path of fertilization.
Key Points
| Feature | Description |
|---|---|
| Proponent | Haberlandt |
| Subject | The role of degenerating nucellus cells in adventive embryogenesis. |
| Mechanism | Dying cells release a stimulus (necrohormone) that triggers adjacent cells to form embryos. |
| Embryo Type | Adventive embryos - those that do not arise from the usual sexual reproduction pathway. |
| Cell Location | Degenerating cells within the nucellus. |
Examples
While the theory is generally discussed in the context of plant reproduction, here are some practical points to consider:
- Citrus Fruit: This kind of adventive embryogenesis is seen in certain species of Citrus, where many embryos develop in a seed from nucellar tissue alongside a zygotic embryo.
- Mango and Other Fruits: Similar patterns can be observed in certain other fruit types where multiple seedlings can develop from one seed, due to this type of asexual reproduction.
Summary
In essence, the Necrohormone theory suggests that the death of certain cells isn’t just an endpoint but a trigger for new life, particularly in the form of adventive embryos. The dying cells release substances that stimulate surrounding cells to develop into new embryos, bypassing the usual method of fertilization. This interesting mechanism expands our understanding of plant reproduction and development.
