We will now look at parenchyma, collenchyma and sclerenchyma cells. Together these tissue types are referred to as ground tissues. Ground tissues are located in the region between epidermal and vascular tissue.
Table: Structure and Function of Parenchyma
|Thin-walled cells.||Thin walls allow for close packing and rapid diffusion between cells.|
|Intercellular spaces are present between cells.||Intercellular spaces allow diffusion of gases to occur.|
|Parenchyma cells have large central vacuoles.||This allows the cells to store and regulate ions, waste products and water. Also function in providing support.|
|Specialised parenchyma cells known as chlorenchyma found in plant leaves contain chloroplasts.||This allows them to perform a photosynthetic function and responsible for storage of starch.|
|Some parenchyma cells retain the ability to divide.||Allows replacement of damaged cells.|
Investigation: Observing Parenchyma Cells
To observe the structure of fresh parenchyma cells
- petri dishes or watch glasses
- dissection needles
- iodine solution
- microscopes, microscope slides and cover slips
- Use the dissecting needle to lift off a small piece of the soft banana tissue.
- Put the sample onto a petri dish or watch glass and mash it slightly using the dissecting needle (and a pencil if you want).
- Lift a small sample of the tissue onto a microscope slide on which you already have placed a drop of iodine solution. Put the cover slip on.
- Observe the cells under low power and find a section where the cells are lying separate, not all over each other.
- Enlarge this section and focus carefully to see if you can find nuclei in some of the cells (they will be bigger than the purple plastids and transparent).
- Draw 2 or 3 cells and label.
- Describe the shape of the cells and their wall thickness.
- What are the plastids called which appear purple and what is their function?