Sunflower slants

It has long been known that plants grow directionally, curving and following sunlight to maximise rates of photosynthesis: twelve year olds across the country have demonstrated this in classroom experiments. Now, however, it seems that some plants might not just follow sunlight individually, but whole groups seem to organise into patterns of bending.

Scientists in Argentina have discovered that sunflower plants in crowded fields grow in opposite directions in order to maximise the amount of sunlight each plant receives. This behaviour starts with a ground zero “pioneer” plant that leans at an angle to avoid the shade from nearby sunflowers. This triggers a cascade as neighbouring plants slant in the other direction for the same reason. The chain of events repeats itself until the entire field of sunflowers resembles a zig-zag pattern. As a result, not only does the initial pioneer benefit, but the whole field of leaning plants shows an increased yield of seeds compared to fields where plants are fixed to stand vertically.

Normally, this phenomenon is very hard to spot, as the leaves disguise the slant. Antonio Hall noticed it by chance when he stumbled across an unusually dense field of sunflowers – and being a professor of plant physiology, he had both the inclination and means to explore the pattern further. With further experimentation, he and his team found that different species of sunflowers appear to have different propensities to lean. This implies that the phenomenon has a genetic basis.

It is currently unknown whether any other plants exhibit similar tendencies – the likelihood is that it will soon become apparent in other single-stemmed crops. The findings could eventually have significance in commercial agriculture techniques, but growers must first find a way to sustainably plant crops sufficiently close together before any engineered slant patterns become useful. For now, the discovery is simply another interesting fact for teachers to add to their Key Stage 3 curriculum.