Rice, with a side of weaponry: Swetha Sivakumar on the hidden talents of foodgrains
We tend to think of the plant kingdom as passive, and the animal kingdom as the aggressive one.
The truth is, plants are master strategists, chemists, engineers, survivalists and tricksters. Even the staples on our dinner plates, from rice and rye to barley, maize and quinoa, have a range of hidden skills.
Imagine, for instance, being locked underwater and needing to breathe. That’s the everyday challenge for certain varieties of rice. Most plants would suffocate in a flooded field. Paddy, particularly susceptible to weeds, evolved to flourish in such conditions instead, since the standing water suffocated weeds and left them with less competition for nutrients in the soil.
How the plant managed to do this is interesting. Paddy evolved a special tissue called the aerenchyma, which is made up of tiny air tunnels that run from its above-water leaves to its submerged roots. This pipeline keeps the plant oxygenated.
Some deepwater varieties even come with SNORKEL genes (that’s their real name). When floodwaters rise, these genes trigger a growth spurt, sending the stem shooting upward, this keeping the leaves and their air tunnels above water.
Other rice breeds take the opposite route, with a strategy called quiescence. Here, the SUB1A gene sends the plant into a kind of hibernation, conserving energy until the water around it drains away, at which point it revives itself. Both tactics are brilliantly effective.
Rye, meanwhile, isn’t a steely survivor so much as a stealthy assassin.
In its early stages, this plant leaks chemicals called benzoxazinoids into surrounding soil. These act as botanical herbicides, preventing rival seeds (pigweed, lamb’s quarters and a range of others) from sprouting. Rye is so effective at culling such weeds that some farmers mow the plant into their soil before planting their crop, thus reducing the need for synthetic herbicides.
Maize plays a different game. It now has a reputation for guzzling water and requiring vast stores of fertiliser, but some wild varieties in Mexico once carried their own fertilising gel: a sticky, sugary substance that oozed from their aerial roots.
The gel housed nitrogen-fixing bacteria that enriched soil. Sadly, these varieties have faded, as farmers selected instead the types of maize that grew fastest and yielded the largest cobs. Scientists are now trying to breed this capability into modern corn. If they succeed, it could eliminate the need for added fertiliser, reducing the carbon footprint of the crop dramatically as a result.
Quinoa has a secret weapon too: the saponins that form a bitter coating on its seed.
Birds hate it. Bugs hate it. Even humans can expect a mild stomach ache if they eat quinoa without first washing off these chemicals.
Supermarkets today tend to sell “sweet” quinoa (naturally low in these compounds) or pre-washed versions. But processing plants don’t just drain the saponins away. These chemicals are so potent, they can be preserved and used by farmers as natural insecticides. The cosmetics industry uses them as foaming agents too. In medicine, they are being studied for their antifungal and cholesterol-lowering properties.
Meanwhile, because of the saponin it contains, quinoa husk can help control golden apple snail populations, thus protecting rice fields across Asia from a voracious pest. In field trials, a quinoa-based natural pesticide decimated populations of the golden apple snail, without harming the fish in the water around the crop.
That’s something to think about, the next time one is standing before a green field. It may seem placid, as it rustles quietly in the breeze, but there’s plenty going on between the leaves.
(To reach Swetha Sivakumar with questions or feedback, email upgrademyfood@gmail.com. The views expressed are personal)
