Q.Micropropagation can be achieved by (A) Self-pollination (B) Asexual reproduction (C) Tissue culture (D) Vegetative propagation
Concept understanding — Meristem Culture
Let’s start with something you already know. When you prune a rose bush or cut the tip off a mint plant, it doesn’t die — it grows back, often bushier. That happens because plants keep a reserve of “baby cells” at their growing tips. These cells are called meristematic cells, and they are the plant’s version of stem cells: undifferentiated, ever-dividing, and capable of turning into any part of the plant.
Now, Meristem Culture is a laboratory technique where you take a tiny piece of that growing tip (the meristem) and grow it in a sterile, nutrient-rich medium. The goal is to produce a whole new plant from that tiny piece — a clone of the original. It’s a form of micropropagation, but with a special twist: the meristem is usually free of viruses, so the new plant is also virus-free.
Meristem culture is the only reliable method to produce virus-free plants from an infected parent plant. This is because viruses cannot reach the actively dividing meristem cells — they travel through the plant’s vascular tissue, which the meristem lacks.
Here’s why this matters in agriculture and horticulture:
- Disease elimination: Many cash crops (potato, sugarcane, banana, cassava) accumulate viruses over generations. Meristem culture lets farmers start with clean stock.
- Rapid multiplication: A single meristem can yield thousands of identical plants in a year — far faster than traditional cuttings or seeds.
- Conservation: Rare or endangered plant species can be multiplied without harming the parent plant.
- Uniformity: All plants are genetically identical (clones), so they flower, fruit, and respond to fertilisers at the same time — ideal for commercial farming.
The NCERT textbook (Class 12 Biology, Chapter 9 — Strategies for Enhancement in Food Production) mentions meristem culture under tissue culture and specifically highlights its use in producing virus-free plants. The textbook example: sugarcane and banana are routinely cleaned of viruses using this method.
Meristem culture is not the same as ordinary tissue culture. In ordinary tissue culture, you can use any part of the plant (leaf, stem, root). In meristem culture, you specifically use the shoot apical meristem — the dome of cells at the very tip of a growing shoot. That’s what makes it virus-free.
To visualise it: imagine a plant that has a viral infection in its leaves and stems. If you take a cutting from that plant, the new plant will also be infected. But if you carefully dissect out the tiny, white, dome-shaped meristem (about 0.1–0.5 mm in size) and place it on a sterile gel with nutrients and hormones, it will grow into a healthy, virus-free plantlet. That plantlet can then be multiplied further.
In short: Meristem culture = taking the plant’s “clean” growth engine and using it to mass-produce healthy, identical plants. It’s a cornerstone of modern agriculture, especially for crops that are propagated vegetatively (by cuttings, tubers, or suckers) rather than by seeds.
Meristem culture is part of the NCERT Class 12 Biology chapter on Strategies for Enhancement in Food Production, often searched as "meristem culture virus free plants class 12" or "micropropagation important questions." It regularly features in CBSE board exams and is a useful applied-biology example for NEET's plant biotechnology questions.
Part (a): Micropropagation — mass clonal multiplication of plants from small explants in vitro — is achieved by tissue culture, so the answer is (C). Part (b): The everyday kitchen microbes are Lactobacillus and yeast, so the answer is (A).
Micropropagation means growing many plants from a very small piece of tissue (an explant). Because plant cells are totipotent, an explant placed on a sterile nutrient medium containing the right growth regulators can grow into a callus and then regenerate into thousands of genetically identical plantlets — all done in the laboratory (in vitro).
Checking the options: self-pollination (A) is sexual reproduction and gives variable seed progeny; asexual reproduction (B) is too broad; vegetative propagation (D) is done in vivo on whole plants and yields only a few plants. Only tissue culture (C) provides the sterile, rapid, mass multiplication that defines micropropagation (and can also give virus-free plants via meristem culture).
Micropropagation is achieved by tissue culture — option (C).
Concept understanding — Microbial Fermentation Foods
Let’s begin with something you already know. Think of a pot of milk left out in warm weather. After a few hours, it turns sour and thickens into curd. That change is not spoilage in the usual sense — it is a controlled transformation caused by tiny living organisms called microbes. This is the heart of microbial fermentation.
Fermentation is a process in which microorganisms — bacteria, yeast, or moulds — break down organic substances (like sugars) in the absence of oxygen, producing energy for themselves and, as a by‑product, substances that change the food. When we deliberately use this process to make food, we call the result microbial fermented foods.
You have eaten many of them without thinking twice: curd (yogurt), idli and dosa batter, bread, cheese, pickles, vinegar, and even the dark chocolate you might enjoy. Each of these relies on specific microbes doing their work.
The NCERT textbook (Class XII, Biology, Chapter 10: Microbes in Human Welfare) introduces fermented foods under the topic “Microbes in Household Products.” It lists curd, cheese, idli, dosa, and bread as common examples. The key point is that these are not modern inventions — they have been part of Indian and global diets for centuries.
Why does this matter? Because fermentation does three things that are valuable for us:
- Preserves food — The acids or alcohol produced by microbes prevent spoilage by harmful bacteria. Pickles stay edible for months because of lactic acid from fermentation.
- Improves digestibility — Microbes break down complex molecules. Lactose in milk becomes easier to digest in curd; the proteins in soy become more digestible in tempeh.
- Enhances flavour and texture — The tang of yogurt, the airy holes in bread, the umami of soy sauce — all come from fermentation.
Let’s look at a few examples from your daily life, as the NCERT would describe them:
- Curd (yogurt): Milk is boiled and cooled, then a small amount of previous curd (containing Lactobacillus bacteria) is added. The bacteria convert lactose into lactic acid, which thickens the milk and gives it a sour taste.
- Idli and dosa batter: Rice and urad dal are soaked, ground, and left to ferment overnight. Naturally occurring Leuconostoc and other bacteria produce carbon dioxide gas, which makes the batter rise and gives idlis their spongy texture.
- Bread: Baker’s yeast (Saccharomyces cerevisiae) ferments the sugars in dough, releasing carbon dioxide that makes the dough rise. The alcohol produced evaporates during baking.
- Cheese: Milk is curdled using rennet (an enzyme) or acid, then specific bacteria and moulds are added to ripen it. Different microbes give different cheeses their distinct flavours — for example, Penicillium roqueforti gives blue cheese its veins and sharp taste.
The NCERT emphasises that these processes are not random. They require specific conditions — temperature, pH, moisture, and the right starter culture. If the conditions go wrong, harmful microbes can grow instead. That is why traditional methods (like adding a spoonful of previous curd) are actually precise microbial techniques passed down through generations.
For a commerce or humanities student, the relevance goes beyond the kitchen. Fermented foods are a multi‑billion‑dollar industry. They involve supply chains (milk, grains, fruits), processing technology, quality control, and marketing. Understanding the basic science helps you see why a product like yogurt has a “use by” date, why some cheeses are expensive, and why traditional foods like kimchi or kombucha have become global trends.
In short: microbial fermentation is nature’s way of transforming food using invisible helpers. It is a bridge between biology and everyday life — and it has been feeding humanity long before anyone knew what a microbe was.
Microbial fermentation is a well-established topic in the NCERT Class 12 Biology curriculum, commonly explored through searches like "Microbial Fermentation Foods: definition, examples and applications" and "list microbes used in food production" ahead of CBSE board exams. Students preparing for NEET and other competitive exams often revise this alongside "Microbes in Human Welfare important questions," since it links directly to biotechnology and industrial microbiology.
Part (a): Micropropagation — mass clonal multiplication of plants from small explants in vitro — is achieved by tissue culture, so the answer is (C). Part (b): The everyday kitchen microbes are Lactobacillus and yeast, so the answer is (A).
Humans have long used microbes to prepare food. In the kitchen, the two most common are:
- Lactobacillus — lactic-acid bacteria that ferment the lactose of milk into lactic acid, converting milk into curd/yoghurt (and also used in pickling).
- Yeast (Saccharomyces cerevisiae) — ferments sugars to produce CO₂ that makes dough rise for bread, and is used with bacteria in fermenting idli/dosa batter.
The other options are wrong: Penicillium is used industrially (antibiotics, cheese ripening) not routinely at home; Microsporum and E. coli are not food microbes; Rhizopus is far less commonly used in everyday kitchens than yeast.
The microbes commonly used in kitchens are Lactobacillus and Yeast — option (A).
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