Carnivorous plants prefer to kill in broad daylight

I owe thanks to Dr Andrej Pavlovič for being a patient guinea pig with my first press-release (you can find it on Science Daily) and to Lizzie Shannon-Little at OUP for help­ing put it out. It’s good tim­ing because another paper by Pavlovič on car­ni­vor­ous plants and pho­to­syn­thesis is now a year old — which makes it free to access.

Feeding enhances pho­to­syn­thetic effi­ciency in the car­ni­vor­ous pitcher plant Nepenthes talan­gen­sis is a good part­ner paper to Trap clos­ure and prey reten­tion in Venus flytrap (Dionaea mus­cip­ula) tem­por­ar­ily reduces pho­to­syn­thesis and stim­u­lates res­pir­a­tion. They both cover the costs of car­ni­vory. I can see why a Venus Flytrap has a cost, there’s move­ment as the lobes shut on the prey, but I had expec­ted pitcher plants to be much more pass­ive. They just sit there don’t they?

Poisonous Pitcher plant — The Private Life of Plants — David Attenborough — BBC wildlife

It’s a fant­ast­ic­ally sin­is­ter exhal­a­tion on the video when the traps open. It’s gra­tu­it­ous mon­ster­i­fic­a­tion of a plant, but there’s some key points in there. The trap is formed from some­thing that you’d expect to be pho­to­syn­thes­ising. It’s also a com­plex trap it requires main­ten­ance and upkeep. That’s a cost that has to be paid for with increased res­pir­a­tion. It’s obvi­ously a cost that can be paid, else plants wouldn’t eat meat, but it’s still rare for them to do so. That sug­gests that the costs are non-trivial so a cost-benefit ana­lysis of pitcher plants could tell us some­thing really use­ful about what the plants are doing.

Nepenthes talangensis - Pitcher plant
Nepenthes talan­gen­sis. Source: Wikipedia.

The idea for examin­ing this, like a lot of the best ideas, was very simple. You con­trol the light intens­ity, feed one sample set of pitcher plants with insect lar­vae and see what hap­pens. In this case see­ing what hap­pens involved meas­ur­ing the gas exchange and chloro­phyll fluor­es­cence of the plants and cor­rel­at­ing that with nitro­gen, car­bon and chloro­phyll con­cen­tra­tions, but the basic idea was eleg­antly simple.

The res­ults were also very straight for­ward. The fed lam­inae showed an increase in pho­to­syn­thesis com­pared to the unfed lam­inae. However, for the pitch­ers there was no dif­fer­ence in their pho­to­syn­thesis regard­less of whether or not they were fed. Pavlovič found that bene­fits of feed­ing greatly increased when light intens­ity increased too. The con­clu­sion is that car­ni­vory is a big advant­age when in nitrogen-poor soils and sunny climes. It’s there­fore no sur­prise to find that Nepenthes talan­gen­sis lives in nitrogen-poor soils in Sumatra.

Another find­ing was that only the fed plants flowered. It emphas­ises the import­ance of the pitch­ers in gain­ing nutri­ents for the plant.

Alas for people who like their car­ni­vor­ous plants to be mon­sters Pavlovič’s work is bad news. You’re unlikely to wander through a dark forest fall prey to man-eating plant. There wouldn’t be enough light to make it work. Indeed any­where dark, which is where the best mon­sters lurk, would be bad news for a car­ni­vor­ous plant. Therefore if you want a mon­ster plant you’d need a well-lit shop of horrors.

Alun Salt. ORCID 0000-0002-1261-4283

When he's not the web developer for AoB Blog, Alun Salt researches something that could be mistaken for the archaeology of science. His current research is about whether there's such a thing as scientific heritage and if there is how would you recognise it?