When pollinators land on a flower, they have a mission: They search for sweet nectar to eat and nutritious pollen particles to bring to their young.
But how do insects know where to find pollen? In theory, the process is easy: A flower flaunts chunks of tasty, aromatic powder in plain sight, allowing pollinators to know where to go immediately. But the reality is quite different. “The plant is not interested in giving an honest signal,” he said. Casper van der Kooibiologist who studies the evolution of flower color at the University of Groningen, the Netherlands.
For plants, pollen is all about reproduction. The goal of creating this powder is to transfer the gametes or reproductive cells from one flower to another flower to create a seed. Plants often need pollinators for that job, but it takes a lot of energy and nutrients to produce pollen. So if insects end up eating the pollen, or if the wrong pollinators get to it first, the energy the plant has invested is wasted, van der Kooi explained.
So for most plants, the pollen is hidden, making an insect’s mission more difficult to accomplish. But a plant can’t be too dishonest, van der Kooi said; Otherwise, the insects will find out about this deception and will stop visiting the plant. So instead of communicating directly, plants often use subtle signals to transmit information, he said. Natalie Hempel de Ibarraprofessor who researches the behavior, senses and cognition of social insects at the University of Exeter in the United Kingdom. get up following certain signs to decide which flowers to visit.
Visual signals are one of the main forms of communication between plants and pollinators. Flowers are colorful and insects have this innate affinity for colorful objects, Hempel de Ibarra said. Some flowers have so-called nectar guides, which are patterns, visible only in the ultraviolet spectrum, that illuminate the path to nectar and/or pollen that an insect can follow. Various studies have documented that these nectar guides, as well as the hue of the flowers themselves, can change color as pollen and nectar supplies decrease. lantana camaraa popular garden plant, it is An example of this type of signage, going from yellow to red.
Smell can also indicate the amount of pollen. Flowers release all kinds of chemical compounds into the air and insects can pick up these so-called olfactory signals. Some plants can adjust the amounts of compounds they release as an additional signal. For example, blueberry flowers have evolved to emit fewer compounds after being pollinated, according to a 2011 study in the journal Annals of botany.
Pollinating insects can also detect other subtle signals. An interesting example is the electric field. Flowers have a weak electric field, Hempel de Ibarra said, and this field is affected by the shape of the flower. It can also be interrupted after an insect visits. Research has shown that bumblebees and some other insects You can detect this alteration using specialized hairs.
But ultimately, the way insects make their decisions to find pollen varies widely between species. Flowers can also develop highly specialized relationships with specific pollinators, thus influencing how insects make their decisions. Some flowers, like dandelions, have their pollen on display, which attracts a whole array of pollinators, Hempel de Ibarra said. But tomato flowers, which specifically rely on bees for buzz pollination, hide their pollen in special structures to attract this specific insect.
Additionally, different insects are attracted to specific colors, van der Kooi said. For example, flies tend to gravitate toward yellow, while bees prefer blue.
Decision making can even vary between individuals. Hempel de Ibarra, who studies bees, said individuals within a social colony can make different decisions in collecting pollen as they learn and experience the environment around them. “That makes it quite difficult for bees to decide what kind of pollen they should collect,” she said. “It’s such a complex relationship.”