QUESTION: Which tissue occupies the center of the dicot stem?
ANS:
- Pith occupies the center of a dicot stem.
- It is a type of ground tissue found in the center of the stem, surrounded by vascular tissues (xylem and phloem).
- It is primarily composed of parenchyma cells, which have thin cell walls and large central vacuoles.
- The pith provides support to the stem and may also store and transport nutrients within the plant.
- In young stems, the pith is often prominent and occupies a significant portion of the stem’s cross-sectional area.
- As the stem matures, the pith may become less prominent, and in some cases, it may even disintegrate or be replaced by secondary growth.
- It provides structural support to the stem or branch, helping to maintain rigidity and prevent collapse.
- Additionally, the pith aids in the transportation of water and nutrients throughout the plant, playing a role in the overall functioning of the vascular system.
- In some plants, especially those with woody stems, the pith may gradually decrease in size as the plant ages. This is due to the formation of secondary growth, which involves the development of new tissues like wood and bark. As a result, the pith may become less prominent or even disappear completely in older stems.
- The characteristics of pith can vary among different plant species. In some plants, the pith may be filled with air spaces, providing buoyancy and assisting in floatation. In others, the pith may contain specialized cells or structures that serve specific functions, such as storing starch or aiding in water storage.
| Characteristic | Description |
| Location | · Located in the center of stems and branches. |
| Composition |
· Parenchyma cells, which are loosely packed and have thin cell walls |
| Functions | · Provides structural support to stems and branches.
· Assists in water and nutrient transport within the plant. · May store starch, oils, or other substances. · Participates in wound healing and tissue regeneration. |
| Structure | · Parenchyma cells are generally isodiametric or slightly elongated.
· Cell walls are thin, allowing for easy transport of materials. · May contain air spaces (aerenchyma) in some plants for buoyancy or gas exchange. |
| Variation
|
· Characteristics may vary among plant species and plant parts.
· Pith size can change with age: It may be prominent in young stems but decrease or disappear in older woody stems. · Some plants have specialized pith structures, such as diaphragms or fibers for specific functions. |
| Examples
|
· Sunflower
· Elderberry · Grapevine · Corn stalks · Bamboo · Pith helmets |