IN THE SOIL, where plants’ roots meet fungal hyphae, there are trading posts of a type that came into being more than 200m years ago—long before people got around to engaging in similar activities. These meeting places are the exchanges where plants provide fungi with nutrient molecules, such as sugars and fats, that they make by photosynthesis, in exchange for raw materials like nitrates and phosphates, which fungi are adept at collecting from the surrounding area.
That much is well established. Botanists have long wondered, however, how the details change when resources become patchy, and thus scarce in some places and abundant in others. A study just published in Current Biology by Toby Kiers of the Free University of Amsterdam suggests that, like cunning merchants who know how to make a profit, fungi exploit resource scarcity by marking up their prices. They demand more nutrients from plants in return for their valuable mineral commodities.
Such canniness has long been suspected. But proving it means tracking the raw materials as they are collected and distributed. That has proved tricky. Dr Kiers, though, thought she could do it using structures called quantum dots.
A quantum dot is a mote of matter a few nanometres across. It is made of a semiconducting material capable of...