Question

Canada balsam, a mounting agent used to make permanent slides, is obtained from the species of
A. Abies
B. Cedrus
C. Pinus
D. Juniperus

Answer 1

Hint: Abies is the genus to which fir trees belong. Canada balsam is a resin obtained from Balsam fir trees.

Complete answer:
1.Mounting medium is the chemical in which biological samples are placed when used for imaging under a microscope.
2.Canada Balsam is collected from bark of Balsam first found in forests of North America. Firs belong to the genus Abies. Scientific name of the Balsam fir tree is Abies balsamea.
3.The natural exudate (obtained from fir trees) when heated leaves behind a resin with a refractive index in the range of 1.52-1.55. This is close to the refractive index of crown glass and other glass material used for making lenses in microscopes. Due to its high refractive index Canada Balsam is used as a mounting medium and was previously employed to glue lenses together.
4.In addition to the uses due to its refractive index Canada Balsam was used by indigenous communities for medicinal purposes.
5.The genus Cedrus includes trees such as Cedars. These are native to Mediterranean regions and Western Himalayan mountains. Cedarwood has a distinct smell and cedarwood oil can act as moth repellent.
6.The genus Pinus includes trees such as pine. This genus is currently represented by 11 extant species of shrubs and trees.
7.The genus Juniperus includes Juniper trees.

Hence the correct answer is OPTION(A)

Note: All the above-mentioned genera are conifers. However, Canada Balsam is produced only from specific firs and not from other conifers. After the discovery of different epoxy resins, Canada balsam as a glue for lenses has been replaced with these resins.