Question

Longest cells in the plant kingdom are the sclerenchyma fibres 55 cms. long, they belong to
(a)Linum usitatissimum
(b)Figs
(c)Musa textilis
(d)Boehmeria nivea

Answer 1

Hint: These plants have cellulose cell walls and they are extremely soft and elastic. Therefore this plant is well suited for the processing of textiles while others are highly thicked-walled of lignin or cellulose-lignin.

Complete answer:
The longest cells in the plant kingdom are the sclerenchyma fibres of Boehmeria nivea. This plant is the oldest one and is named as Ramie. Ramie is one of the oldest fibre crops, and has been principally used for fabric production. It is a bast fibres, and the part used is the bark (phloem) of the vegetative stalks.

Additional Information: -Sclerenchymatous tissues are highly thickened walled made up of cellulose, lignin or both. A few to numerous pits occur in the walled.
-This tissue is of two types-sclerenchyma fibres and sclereids
-Fibres are highly elongated, narrow and spindle-shaped. On maturity they become dead.
-This tissues majorly provide mechanical strength to leaves, petiole, etc. Also these are commercial in nature. Example - jute, flex, hemp.
-Sclereids are highly thickened dead sclerenchyma cells, with narrow cavities. These are bordered cells and vary in shape from polyhedral to cylindrical.
-This provides stiffness to the parts of the plants. For example- guava, apple, sapota.
-Musa textilis has hard fibres due to presence of a high proportion of lignin in the cell wall.
-Figs have sclereids in their fruits, which impart hardness and strength.
So, the correct answer is ‘Boehmeria nivea’.

Note: -Living fibres occur in Tamarix aphylla as they possess nucleated protoplasts.
-Sclereids form stony endocarps of many fruits called stone fruits. E.g.- almond, coconut.