Sinapyl alcohol

Transcription

Lignin Staining Lignin, a complex phenylpropanoid polymer, is primarily deposited in the walls of cells that have secondary wall thickening, such as tracheary elements and fibers. Lignin provides mechanical strength to the walls of these sclerenchyma cells. Lignin is derived from the de-hydrogenative polymerization of the monolignols p-coumaryl alcohol, coniferyl alcohol, and sinapyl alcohol. These monolignols are synthesized through a phenylpropanoid biosynthetic pathway. In the top part of the stem, where the only sclerenchyma cells present are the xylem vessel elements, lignin staining is only seen in the xylem. In the middle part of the stem, another type of sclerenchyma cells - the inter-fascicular fibers is present in addition to xylem cells. Here lignin is seen in both inter-fascicular fibers and xylem cells. In the lower part of the stem, more xylem cells and inter-fascicular fibers are formed. Consistently, intense lignin staining is seen in these sclerenchyma cells too. No lignin staining can be detected in the cortical cells or the pith parenchyma cells throughout the stems. Materials Required Potato Stem of the plant Double edged razor blade Water Dropper Brush Glass slide Blotting paper Phloroglucinol Stain (colorless liquid) Petri dish PROCEDURE Using a razor blade cut the potato into a block and make a slit in the middle of the potato block. Place the stem of the plant in the middle of the slit made in the potato block. Cut thin sections of the stem along with the potato block into a Petridish containing water. Using a brush transfer the cut sections of the stem into a Petridish containing water. Pour few drops of phloroglucinol-HCL stain into a watch glass using a dropper. Transfer the cut sections of the stem from the Petridish into the watch glass using a brush. Take a clean glass slide and pour few drops of water on to the slide. Using a wet brush transfer the sections from the watch glass onto the slide. Place a coverslip over the sections on the slide using a forceps. Remove the excess solution from the edges of the coverslip by touching the side with a blotting paper and observe the slide under microscope. RESULT The red colour seen in the sections indicate Lignin staining. Lignin staining is heavy in both xylem cells and inter-fascicular fibers.