STUDY OF DISTRIBUTION OF TISSUE SYSTEM IN DICOT STEM
A young slender stem of a dicot plant is to be collected from surroundings. Any plant such as Ban Sharisha (Rorippa indiea Muktajhuri (Acalypha indica) may be chosen. Ricinus (Verenda) stem is wider in breath. It may not be possible for the student to cut a transvers section of it. In such case this type of broader stem may be splitted.
longitudinally before cutting transverse section at this stage. It is sufficient to show the cuticle on the epidermis, circular arrangement of vascular bundles. and in each vascular bundle xylem and phloem tissues are present.]
Materials required: A piece of stem of any dicot plant, microscope, watchglass. water, sharp blade, safranin solution (red dye), brush, slide and cover slip etc.
Procedure: Holding the young stem with the left hand, very thin section(transverse section) is to be taken by a sharp blade holding in the right hand. Water should be placed at the edge of the blade and on the cutting end of the stem so that air does not enter into the section. Sections are to be kept in water taken in a watch glass. A drop of water is to be placed on the slide and then a uniformly thin section should be taken by a brush and placed in the water drop on the slide. A little amount of safranin solution is to be added in the water drop on the slide. Then a cover slip is to be placed over the section and the section would be observed under a compound microscope.
Observation: In cross section the stem will appear more or less circular inshape. In observation the following tissue system will be seen: A single layered parenchymatous cells present at the outermost position of the section; this is epidermal tissue, it is called epidermis. Outside the epidermis there is a layerof cuticle. In some plant unicellular or multicellular hairs may develop here and there from epidermal cells. Inside the circular layer towards the middle of the section there is another circular layer. Vascular bundles are encircled by this layer and are arranged in a ring. Each vascular bundle consisting of phloem tissue towards the periphery, a thin cambium layer (not easily visible) in the middle and xylem tissue towards the center. The vascular bundles together form the vascular tissue system. The zone in between epidermis and vascular region is called the cortex. It is the ground tissue system. The region surrounded by the vascular tissue is known as pith, which is also ground tissue.
Conclusion: Cuticle present on the epidermis, xylem and phloem tissues arepresent in each vascular bundle. So the section is of a young stem. Vascular bundles are arranged in a ring, cambium present in between xylem and phloem, so the section is of a stem of Dicot plant.