Physiology of milletsMinistry of Agriculture and Farmers Welfare
What are millets?
Millets are a group of small-seeded grasses grown as crops for their edible grains. Millets have been cultivated across Africa and Asia for thousands of years, and exhibit significant genetic diversity based on where they're growing, adapting to a range of climatic and soil conditions. They can also withstand drought and temperatures as high as 50°C. So what makes them adaptable?
Millets go deep, making them water-prudent
Millets have specialized root systems that can penetrate deep into the soil, allowing them to access water and nutrients from lower soil layers. This deep root system helps them withstand drought conditions and utilize water sources that may not be available to other crops with shallower roots.
Millets know how to keep things cool
Millets are able to cope with high temperatures thanks to a couple of factors, including smaller and narrower leaves compared to other cereal crops. This leaf structure reduces the surface area exposed to the sun, minimizing water loss through transpiration.
Stomatal regulation is another way to deal with heat stress. Stomata are small openings on the surface of leaves that control gas exchange, including the release of water vapour. Millets have the ability to regulate their stomata to minimize water loss - they can partially close their stomata during the day, reducing the transpiration rate and conserving water, without compromising photosynthesis.
Millets have another defense mechanism against blazing temperatures: They produce specific proteins known as heat shock proteins (HSPs) in response to high temperatures.
Heat shock proteins help protect plant cells from heat-induced damage and maintain their normal functions. These proteins act as molecular chaperones, ensuring proper functioning of plant cells under heat stress.
Millets have a photosynthesis hack
Millets exhibit C4 photosynthesis, a type of synthesis that’s more efficient in hot and dry climates than C3 photosynthesis. This physiological pathway enables them to efficiently use carbon dioxide, and minimize water loss through their leaf stomata.
C4 photosynthesis also contributes to millets’ higher biomass, which in turn helps to regenerate the soil they grow in.
Millets know how to escape drought
Millets have a relatively short life cycle (60-120 days), meaning they complete their growth and reproduction quickly. They also exhibit an amazing characteristic called drought escape or avoidance - by which they mature even more rapidly, completing their life cycle and producing grains before the onset of severe drought conditions.
Some millet varieties can also adjust their growth patterns in response to limited water availability.
Millets are resistant to pests
Millets have a tough outer hull that pests find difficult to penetrate. They also contain tannins (which can cause insects to dehydrate and die), flavonoids (a plant-based chemical that can act as an anti-oxidant and protect plants from pest damage) and saponins, which make them unattractive to pests and insects.
This, in turn, reduces farmer reliance on synthetic pesticides.
Millets are less dependent on fertilisers, therefore making them superior to other grains.
Millets adapt to the soils they grow in
Millets can grow well in a variety of soil types, including those with low fertility or high salinity. Millets exhibit salt exclusion and tolerance - ie they can exclude salt from their roots or tolerate it within their tissues.
Some millet varieties have specialized root structures and transporters that actively block the uptake of excessive salt from the soil, whereas others possess the ability to accumulate salt in their older or senescent tissues, effectively sequestering it away from actively growing and essential parts of the plant.
Text and images courtesy Ministry of Agriculture & Farmers Welfare, Government of India
