Making grasses more digestible promises improved feed for ruminants and better biomass for biofuel production, with economic and environmental benefits for both.
Plant biomass contains considerable calorific value but most of it makes up robust cell walls, an unappetising evolutionary advantage that helped grasses to survive foragers and prosper for more than 60 million years.
The trouble is that this robustness still makes them less digestible in the rumen of cows and sheep and difficult to process in bioenergy refineries for ethanol fuel.
When they are attacked by herbivores, many plants call in reinforcements. To this end, they emit odours. These odours attract wasps, for example, that are parasites and in search for host animals. The wasps lay their eggs into the caterpillars, thereby killing them: this means fewer butterflies and voracious caterpillars in the next generation.
An international research team has tested the effects of twelve types of herbivores on field mustard (Brassica rapa). The researchers found that the plants consistently adapt the odours they emit upon attack to the characteristics of the respective herbivore. This helps the plant to specifically attract natural enemies that feed on the herbivores eating them. Most surprisingly, they emit different odour bouquets in response to exotic as opposed to native herbivores.