A single pollen grain failing inside a toor dal flower is why your dal gets costly. Climate change has made that failure routine across India's growing belt. (Photo: Getty)

Burnt flowers, empty bowls: How heat above 32°C makes your favourite dal costly

Climate on My Plate is India Today Science's new series on how the climate crisis is reshaping the everyday things you eat, drink, buy and own. This week, it is your favourite dal, and how heat is emptying your bowl.

by · India Today

In Short

  • Toor dal flowers abort when temperatures cross 32 degrees Celsius.
  • Pollens and pods in pigeon pea drop by 40 per cent under heat stress.
  • India's toor dal production fell short by over one million tonnes in 2024.

Every time you pressure-cook a handful of toor dal, you are holding the product of a delicate biological process that heat is quietly destroying.

India produces around 3 to 4.3 million tonnes of toor dal annually, while domestic consumption demand stands at 4.5 million tonnes, leaving a persistent shortfall that forces imports every year.

Dal feeds over a billion Indians every single day. And it is under serious threat.

This is the latest story in Climate on My Plate, India Today Science’s new series on how the climate crisis is reshaping the everyday things you eat, drink, buy and own. This week, it is the savoury toor dal you crave.

WHY IS HEAT KILLING TOOR DAL BEFORE IT REACHES YOUR PLATE?

Toor dal is a warm-season crop, but it has strict temperature limits. It grows best between 26 and 30 degrees Celsius.

Once temperatures cross 32 degrees Celsius during the flowering stage, something irreversible happens inside the plant: pollen grains fail.

Pollen failure is not a metaphor, but a measurable biological event. When temperatures cross the threshold, pollen loses viability, which means it can no longer fertilise the flower.

Rising temperatures during flowering are causing widespread pod loss in toor dal flowers, pushing retail prices past Rs 200 a kg. (Photo: Getty)

The flower then drops from the plant entirely, a process scientists call floral abortion. No flower means no pod. No pod means no dal.

India's average temperatures have already crossed that threshold across large parts of the toor-growing belt.

India's temperatures have been rising steadily across seasons.

According to data analysed by the India Meteorological Department and published in a Springer Nature chapter, annual mean, maximum and minimum temperatures across India showed a warming trend of 0.15 degrees Celsius per decade between 1986 and 2015, with pre-monsoon warming running even higher at 0.26 to 0.29 degrees Celsius per decade.

WHAT HAPPENS INSIDE A TOOR DAL FLOWER WHEN IT IS TOO HOT?

The damage begins long before the flower falls. Heat stress disrupts pollen tube growth, the biological mechanism through which a pollen grain travels to fertilise the ovule inside the flower.

Without successful fertilisation, the plant has no reason to sustain the flower and sheds it.

India's toor dal production fell short by over one million tonnes in 2024, forcing costly imports and driving up retail prices. (Photo: Getty)

Research confirms that heat stress during the reproductive stage directly affects pollen viability, fertilisation, and pod set in grain legumes.

The optimum temperature for cultivated pigeon pea is between 25 and 35 degrees Celsius.

Temperature-dependent decreases in the levels of auxins, a crucial plant hormone that regulates growth and environmental responses, under heat stress hamper normal cell wall development and contribute to male sterility in the crop, according to a study published in New Phytologist.

The effect compounds. Toor dal is a long-duration crop. It flowers across several weeks, and if each spell of heat causes another round of floral abortion, the cumulative pod loss can devastate an entire harvest.

WHY ARE ERRATIC RAINS MAKING THINGS WORSE?

Heat is not the only problem. Toor dal needs moisture during pod development but cannot tolerate waterlogging during flowering.

Climate change is delivering both extremes at the wrong times.

The Council on Energy, Environment and Water documented that 55 per cent of India’s agricultural districts experienced a shift in rainfall patterns between 2013 and 2022, with intense downpours replacing steady rain.

Once temperatures cross 32 degrees Celsius, toor dal's pollen grains lose viability and flowers fall before pods can form. (Photo: Getty)

When heavy rain arrives mid-flowering, it washes pollen off flowers before fertilisation can occur.

When the dry spell that follows is hotter than usual, the next flush of flowers aborts again.

Maharashtra, which accounts for nearly 28 per cent of India's toor dal production and ranks first in both area and output

WHY DOES A FAILED POLLEN GRAIN COST YOU RS 200 A KG?

The answer is simple arithmetic. Fewer pods per plant means less dal per hectare.

Less dal per hectare means tighter supply. Tighter supply means higher prices.

Retail toor dal prices in India crossed Rs 200 per kg in late 2024, the highest in over a decade, according to data from the Department of Consumer Affairs.

India's total annual requirement for toor dal is 4.5 million tonnes, while domestic production has consistently fallen short, forcing the government to permit large-scale duty-free imports from Mozambique, Tanzania and Myanmar to bridge the gap, according to the India Pulses and Grains Association.

Just 6 hours of heat above 33 degrees Celsius during flowering of toor dal can reduce pod set by up to 40 per cent. (Photo: Getty)

That import cost gets passed down the supply chain directly to your kitchen.

The dal bowl on your table is not just a staple.

It is a receipt for everything climate change is doing to a single pollen grain in a field you will never visit.

#ClimateOnMyPlate

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