Stem fibre or Bast fibre (also known as phloem fibre or skin fibre) is a type of plant fibre obtained from the phloem (the "inner bark," also known as "skin") or bast surrounding the stem of certain dicotyledonous plants. It strengthens the stem and supports the conductive cells of the phloem. Some of the most economically important bast fibres are obtained from agricultural herbs, such as flax, hemp, or ramie, but bast fibres from wild plants, such as stinging nettle, and trees such as lime or linden, willow, oak, wisteria, and mulberry have also been used in the past. Bast fibres are soft and flexible. Fibres from monocotyledonous plants, known as "leaf fibre," are stiff and hard. In this article, we will discuss Stem Fibres which will be helpful for UPSC exam preparation.

What are Stem Fibres?

• Stem fibres or bast fibres are those derived from the outer cell layers of stems of various plants.
• Flax, jute, hemp, ramie, and kenaf are among the most commonly used plants for the production of bast fibres.
• Because these are annual crops, there is a plentiful supply of materials, and they are gaining popularity in a number of nonwood composite manufacturing processes.
• Fibers are found in bundles or aggregates. The bundles are made up of 10 to 25 elementary fibres with lengths ranging from 2 to 5 mm and diameters ranging from 10 to 50 m.
• The bundles are linked together by lateral ramification, resulting in a three-dimensional network.
• The elementary fibrils and bundles are held together by lignin and pectin intercellular substances, which must be removed during the extraction process.
• These fibres are made up of a network of tube-like cell walls. Each cell wall has primary, secondary, and tertiary (S1, S2, and S3) layers.
• The fibres can be much longer than wood fibres, with hemp, for example, having lengths of 20 mm.
• Because these fibres contain less lignin than wood fibres, their cellulose content is higher.
• The cellulose in bast fibres is also more crystalline (80-90%) than that in wood fibres (50-70%).

Examples of Stem Fibres

Flax

• Flax fibre is extracted from the stems of the plant Linum usitatissimum.
• Fibres run along the surface of the plant stem, which is about 1 m tall and 2-3 mm thick in diameter.
• Flax fibre is a cellulose fibre like cotton, but its structure is more crystalline, making it stronger, stiffer to handle, and more easily wrinkled.
• The molecular fine structure of flax fibre is controlled by the plant growing conditions and the retting procedure used.

Jute

• Jute is a natural fibre derived from the bark of the white jute plant Corchorus capsularis and, to a lesser extent, tossa jute (Corchorus olitorius).
• Jute is a long, soft, and shiny fibre that can be spun into coarse, strong threads and is one of the least expensive natural fibres.
• It is also the most versatile, eco-friendly, natural, long-lasting, and antistatic fibre available.
• The plants are retted in the same manner as flax. The resulting jute strands, which can be up to 3 m long, are made up of many very short fibres, elementary fibres (length 0.5-6.0 mm, diameter 26-30 m) held together by lignocelluloses.
• The fibres contain between 61% to 71% cellulose, a significant amount of hemicelluloses (14-20%), lignin (12-13%), and pectin (0.2%).

Hemp

• Hemp is a bast fibre derived from the stems of Cannabis sativa L plants.
• It grows quickly to a height of 4 m without the use of agrochemicals and captures a large amount of carbon.
• The most important components of fibres are cellulose (77%), pectin (1.4%), and waxes (1.4%).
• Pectin is found in the middle lamellae and binds the elementary fibres together to form bundles.
• The lignin (1.7%) is an incrusting component of the fibre. It is incrusting cellulose and contributes to the hardness and strength of fibres. It is found in the middle lamellae and primary cell wall of the fibre.
• Tannin, resins, fats, proteins, and other components of hemp fibres are also present. Hemp contains far more of these components than cotton.

Mesta

• Mesta is an annual herbaceous plant. It is the third most important commercial crop after cotton and jute. Its origins can be traced back to Afro-Asian countries.
• The plant's stem or bark is used to make fibre.
• Mesta refers to two species of Hibiscus, Hibiscus cannabinus and Hibiscus sabdariffa.
• Hibiscus Sabdariffa is a drought-resistant variety, whereas canabiscus grows well in areas with 50-90 mm of rainfall because it is a short-season variety.
• Major mesta growing states include Maharashtra, Andhra Pradesh, West Bengal, Bihar, Orissa, Meghalaya, Karnataka, and Tripura.
• Mesta can be grown in a variety of soil conditions. It produces the best results when grown in rich loamy soil.
• Acidic and wet soils are not suitable for mesta cultivation.
• The months of May and June are ideal for sowing mesta crops.

Ramie

• Ramie is a herbaceous perennial plant native to eastern Asia in the nettle family Urticaceae.
• Ramie fibres are extracted from the stem of the nettle plant Boehmeria nivea.
• Individual fibre cells in stems are held together in fibre bundles by waxes, hemicelluloses, lignin, and pectins that are difficult to remove.
• As a result, the efficiency of the retting process commonly used for extracting hemp fibres, for example, is insufficient for extracting ramie fibres from stems.

Kenaf

• Hibiscus cannabinus is used to make kenaf fibres.
• Kenaf has two types of fibres: long bundles in the cortical layer and short bundles in the ligneous zone.
• The lumen varies greatly in thickness along the cell's length and is interrupted several times.
• Kenaf fibres are composed of 45-57% cellulose, 21.5% hemicelluloses, 8-13% lignin, and 3-5% pectin.
• Kenaf fibres are coarse, brittle, and challenging to process.
• Their breaking strength is comparable to that of low-grade jute and is only slightly reduced when wet.
• There are numerous potential specific applications for kenaf whole stalk and outer bast fibres, such as paper products, textiles, composites, building materials, absorbents, and so on.

Conclusion

Bast fibres have a long history of use. They have been in use for over 8000 years. Bast fibres are now used as raw materials not only in the textile industry, but also in modern environmentally friendly composites used in a variety of applications such as building materials, particle boards, insulation boards, food, cosmetics, medicine, and so on.

FAQs

MCQs

1. What is the main characteristic of bast fibres?

A) They come from the leaves of plants
B) They are derived from the outer bark
C) They are obtained from the inner bark or stem
D) They are primarily synthetic fibres

2. Which of the following is a common use of bast fibres?

A) Building materials
B) Packaging and textiles
C) Agricultural machinery
D) Electrical insulation

3. What is one environmental advantage of using bast fibres?

A) They are biodegradable
B) They require a lot of pesticides
C) They are non-renewable
D) They contribute to deforestation

4. Which of the following is an example of a bast fibre?

A) Sisal
B) Jute
C) Cotton
D) Wool

5. Which of the following challenges affect the cultivation of bast fibre crops?

A) Limited irrigation and specialized machinery
B) High labor costs
C) Excessive water requirements
D) High susceptibility to pests

GS Mains Questions and Model Answers

Q1: Discuss the role of bast fibres in promoting sustainable agricultural practices and their impact on the economy.

Answer: Bast fibres, like jute, hemp, and flax, contribute to sustainable agriculture by reducing dependence on synthetic fibres and plastic materials. They require fewer pesticides and fertilizers, supporting organic farming practices. The cultivation of bast fibre crops generates employment, particularly in rural areas, contributing significantly to the agricultural economy. These crops also provide raw materials for industries such as textiles and packaging, promoting economic growth and environmental sustainability.

Q2: How can the cultivation of bast fibres be promoted to enhance rural development in India? Discuss the challenges and potential solutions.

Answer: The cultivation of bast fibres can enhance rural development by providing sustainable livelihoods in farming communities. To promote bast fibres, government incentives such as subsidies for cultivation and investment in processing technologies are needed. Challenges such as limited irrigation, poor market access, and low awareness about bast fibres can be addressed through improved infrastructure, training programs, and better market linkages. Support for small-scale farmers and cooperative models can help them access global markets for bast fibre products.

Q3: Evaluate the economic, environmental, and social benefits of increasing the production of bast fibre crops in India.

Answer: Increasing the production of bast fibre crops in India can provide several benefits. Economically, it supports the textile, packaging, and paper industries, creating jobs and fostering rural entrepreneurship. Environmentally, bast fibres are biodegradable, reducing plastic waste and promoting sustainable farming practices. Socially, the cultivation of these crops provides stable livelihoods for rural populations, particularly in underserved areas, improving rural income and socio-economic development.

Previous Year Questions on Bast Fibres in Agriculture

UPSC CSE 2019

Question: “Examine the importance of bast fibres in the agricultural and industrial sectors. How can the cultivation of these fibres contribute to sustainable agricultural practices?”

Answer: This question explores the significance of bast fibres like jute and flax in both agriculture and industry. The answer should discuss their uses in textiles, packaging, and eco-friendly products. It should also highlight the role of these fibres in promoting organic farming and reducing environmental impact.

UPSC CSE 2020

Question: “What are the challenges and benefits of cultivating bast fibre crops in India? How can the government enhance their production?”

Answer: The challenges include poor irrigation infrastructure, limited market access, and lack of modern processing technology. Benefits include environmental sustainability, job creation, and rural economic development. The government can enhance production by providing subsidies, improving irrigation systems, and promoting research in better farming practices and market access.