Question

Select the correct option:
A transverse section of the stem is stained first with safranin and then with fast green following the usual schedule of double staining for the preparation of a permanent slide. What would be the colour of the stained xylem and phloem?
A. Red and green
B. Green and red
C. Orange and yellow
D. Purple and orange

Answer 1

Hint: Xylem tissue conducts water and mineral nutrients from the soil upward in plant roots and stems. phloem (tissue) transports products of photosynthesis from the leaves, where they are synthesized to other parts of the plant.

Complete Answer:
Staining can be defined as a technique that is used in microscopy to enhance contrast in a microscopic image. The stains and dyes are frequently used to highlight structures in microbes for viewing.
It is to be noted that a large number of natural and synthetic dyes are used as anatomical stains, such as hematoxylin, brazilin, haematein, Bismarck brown, eosin, fast green, safranin, etc.

The sidewalls of the xylem cells are composed of thick lignin. Lignin is a brittle crystalline material giving mechanical strength. Lignin picks up the red dye so the walls appear pinkish. The safranin appears a brilliant red in chromosomes nuclei and lignifies and cutinized cell walls.

The fast green gives a bright green colour to cellulose cells and cytoplasm. Both the colours are permanent and they persist for many years. Safranin stains are red for xylem and fast green stains green for phloem.

Thus, the correct option is A) Red and green.

Note: It is to be noted that on the basis of origin, there are two types of xylem cells:
i. Primary xylem: It originates from procambium and further divides into protoxylem and metaxylem
ii. Secondary xylems: It originates from the vascular cambium.