Why are bees important to plants?

Chris Smith put this question to Beverley Glover from Cambridge University...

Beverley - So back to my same point that actually, most of the things that define how plants function compared to other organisms is that they can't move. They're rooted to the spot. But just like any animal, they need to find a mate and they need to get the male gametes from one plant to the sperm from one plant to the female gamete, to the eggs of another plant. And the way they do that, they have to find somebody else to carry the stuff around for them. And the most successful and most commonly used and most popular thing for a plant to recruit to carry its pollen grains – they contain the sperm – around is a bee. And the reason for that is that bees are pretty smart. They can learn things. They can manipulate complicated structures. They're quite big. They can manage heavy flowers. They’ve got good colour vision. They can read cues and signals in the flower. And so actually, they're really, really good pollen vectors for plants. And an enormous number of plants rely on bees to get the male gametes from one plant to the female side of another. And without the bees, there wouldn’t be an awful lot of plant reproduction going on.

Chris - I did read a paper where scientists were showing that plants lace their nectar with caffeine and this seems to reinforce the memory of the bee for that particular flower strain, and may also give the bee a bit more energy. Now, is this true?

Beverley - It’s a very – it’s a cunning strategy. It’s a lovely paper. Yeah, so the flowers are rewarding the bees for doing this work with pollen and nectar. So pollen is full of nitrogen and nectar is full of sugar. And different bees are collecting one or the other at different times in the colony’s life cycle. And you can put different things into your nectar and pollen to make them more attractive, less attractive or to attract specific insects. So the basics in nectar or sugar and water, there are sometimes other micronutrients in there, the concentration of sugar might vary, the specific type of sugar might vary. And yes, some plants – it’s not that common and the citrus family are quite good at it, put caffeine into their nectar. And the experiments people have done have shown that bees form a search image of those flowers with caffeine in the nectar better and remember them better than they do flowers that don’t have caffeine in their nectar.

Chris - Jess…

Jess - Can I ask a physics related bumble bee question? So bumble bees feel magnetic fields, right? Do other insects feel magnetic fields?

Beverley - We don’t really know yet. There's some work on that and on how that works in perception but insects, it’s an enormous group and there's a lot of different, a lot of variation in there. A lot of them have different visual systems, different sensory systems, and different cognitive systems. So we don’t really know yet who can do what.