A new carnivorous plant – the Candelabra Saxifrage (Saxifraga candelabrum) Image Zhang et al

Dear Readers, when I think about carnivorous plants my mind goes to Venus Flytraps and Sundews and Pitcher Plants. What they share is that they live in low nutrient environments, such as bogs, or are epiphytes, so they grow on other plants without parasitising them. However, increasingly scientists are looking at alpine plants, particularly saxifrages,  to see if they get some of their food by trapping insects, a train of thought that has a history dating back to none other than Charles Darwin himself. The soil in alpine regions is often thin and lacking in nutrients, and so this is another area where ‘eating’ insects might be useful for the plants.

Darwin had long observed that some plants had sticky leaves which seemed to trap insects, and he wondered if the plants gained any benefit from this. He took  two species of Saxifrage which had those sticky leaves – Pyrenean Saxifrage (Saxifraga umbrosa ) and Round-leaved Saxifrage (Saxifraga rotundifolia,) and dipped their leaves into  infusions of raw meat and solutions of ammonia, to see if the leaves would absorb them. Darwin observed that the colour of the cells in the leaves changed and they became more turgid, showing that they’d taken up the fluids. From this, he deduced that some plants, without being completely carnivorous, were able to utilise insects as a source of nutrients, and that this was much more widespread throughout the plant kingdom than had previously been thought. However, the technology at the time wasn’t able to  prove Darwin’s hunch.

This week, experiments on the Candelabra Saxifrage (Saxifraga candelabrum), a close relative of the plants Darwin was studying,  have shown that the plant does indeed catch insects and digest them. Firstly, the team from the Chinese Academy of Sciences noticed that individual plants could have up to 70 small insects trapped on their leaves and stems (larger insects, more useful for pollination, don’t get stuck).

The scientists investigated the chemicals contained in the hairs that trapped the insects, to see if they were capable of digesting the insects – they were. Then, by infusing insect prey with a nitrogen isotope, it was found that the nutrients from the digested insect were taken up by the plant. Finally, genetic analysis showed that the Saxifrage shared genes with other carnivorous plants, which controlled nutrient uptake and digestion.

Research is going forward on other saxifrages. I wonder if scientists could also have a look at the Teasel? I’ve long suspected that this plant might be able to digest the insects that fall into the ‘baths’ at the base of the leaves. And there are probably plenty more plants that can utilise nutrients from insects without being completely reliant on them. Watch this space!

The New Scientist article is here

The research paper is here.