What is Pollination?
At the most basic level, pollination is the way plants achieve fertilization and genetic diversity. Pollination occurs when pollen grains from the male part of one flower (anther) are transferred to the female part (stigma) of another flower. Once pollination occurs, the fertilized flowers produce seeds, which enable the associated plant to reproduce and/or form fruit.
You will notice that we didn’t specifically mention bees. Pollination can occur through many mechanisms, including some without the assistance of another living thing. Pollination through wind is an example.
However, living pollinators such as bees play a huge and valuable role in pollination across the globe. Let’s drill down on how.
Why is Pollination Important?
Benefits to Humans
Pollination provides many benefits to humans, with the most obvious being the abundance of food.
Corn is an example of a crop that needs wind pollination, which means it can thrive without the help of bees. By comparison, peppers and tomatoes are examples of plants that require pollination from insects.
In addition, the food farmers feed to their livestock requires pollination. A lack of pollination therefore even impacts, indirectly, the availability of meat and can result in a limited supply of vegetables, fruits, and nuts.
Because pollination is so critical to the food supply, the insects involved have significant socio-economic value. Many commercial beekeepers rent bees to crop farmers to increase pollination. In the U.S., the almond and blueberry industries are among the biggest renters of bees.
Beyond the renting and profiting from bees, pollination management is a growing career field. Professionals in the industry develop and research technologies that can potentially replace the role of bees and other insects in the pollination process. Over time this may increase in importance due to the alarming decline in pollinator numbers.
This growing field is appealing to engineering and science students who are also invested in the health of the planet. MIT has conducted a study looking at the costs of pollen dusting and hand pollination. They found that it’s more cost-effective to spend money saving bees and other pollinators than it is to use these mechanical methods.
Benefits to Flowers/Plants
Flowers would be nowhere without pollination! No matter the type of pollination involved, plants require pollination to reproduce. Just like every other living thing on the planet, plants are driven to propagate their species and ensure their genetics live on for many generations. Pollination is how plants begin this process.
Pollination allows plants to improve genetic diversity within their species and, in some cases, plants will cross-pollinate with other flower varieties. This creates a heartier, more genetically diverse plant population and sometimes drives a mutation that results in a new species or hybrid.
Benefits to Bees
Bees don’t engage in the pollination process merely because they love flowers and plants! They reap huge benefits from participating in the process. As they fly from flower-to-flower, they move pollen from plant-to-plant on their legs, which is how pollination occurs.
Bees store the pollen they collect in specific comb cells at the edge of the brood nest and use it as nutrition for nurse bees. Nurse bees perform a critical function in the hive – caring for new larvae until they’re able to spin their cocoon. They do this by secreting the nutrition from pollen into royal jelly and making “bee bread”, which is a combination of the pollen they’ve ingested, honey, and enzymes.
Because honey bees use pollen in their reproductive process, they collect it from all plants, even those not requiring cross-pollination via insects. There have been numerous reports that corn sprayed with pesticides results in bees dying because they visit the corn fields for pollen, even though corn relies on wind pollination.
How Bees Find Flowers
From Birth to Foraging
Foraging bees are always female (workers), but they don’t start off foraging right after being born. Instead they progress through several roles before achieving the rank of forager. Their first job begins at the tender age of one or two days old as cleaners.
- Cleaners. Cleaners are responsible for cleaning and polishing used brood cells.
- Undertakers. After successfully mastering the tasks of a cleaner, worker bees move on to be undertakers
- Nurses. Nurse bees are fully responsible for ensuring the health and future development of the hive.
- Builders. After about 12 days, the female bees begin to secrete and produce wax. At this point, they move on to become builders.
- Temperature Regulators. Upon mastering the builder role, the lady bees move on to temperature regulation (it should be noted that drones will occasionally help in temperature regulation too, which is pretty much the only useful thing they do within the hive!).
- Guards. Guard bees are the final role, before becoming a forager. They have a critical role in protecting the hive from robbers and other threats
Around 14 days old, female worker bees are old enough to venture out as foragers. This job means they start leaving the hive at sunrise and visit flowers up to five miles from the hive, in search of nectar and pollen. They may make up to 10 trips a day and will return to the hive at sunset.
Workers typically live around six weeks in the summer and will frequently die in the field while foraging.
Sense of Direction
A bee’s sense of direction is often driven by a sense of smell. Their odor receptors are so plentiful and precise they can detect pollen from several yards away and determine which type of flowers are nearby with exacting precision. The direction of the sun is also a factor.
The flight path to and from a foraging site is implanted in their brain visually and communicated to other inhabitants of the hive in an equally visual manner. Through the waggle dance…
The waggle dance is one of the most unusual methods of animal communication. When a female bee returns from foraging and needs to share the location with her coworkers, she performs a highly complex series of steps. This is called the waggle dance.
Each step of the dance communicates an element of information about the location being described. The length of the waggle indicates the distance from the hive. Every 75 milliseconds of the dance indicate approximately an additional 330 feet to the location.
The vigor of the forager’s dance tells her coworkers how rich the food supply is at the location she’s describing. Additionally, by angling her body in the appropriate direction, she tells her coworkers the exact way to fly to reach the food source. This angle is based upon an imaginary straight line across the bottom of the hive matching the direction of the sun at the time of the dance.
Each time she changes the angle of her body she is indicating where other bees must change direction. Used in conjunction with the length of the dance between these changes, the bees are provided an exact map.
Finally, as she ends her waggle dance, the bee shares the scent of the flowers to be found at the location with her coworkers. They will sniff her with their antennae and add this data to the information they received during the dance.
To continue finding new food supply locations, bees will leave the hive at different points during the waggle dance. Some will stay and learn the exact location of that specific source, while others will fly off as far as they know and then search for and locate their own sites, which they will bring back to the hive – and dance.
See a waggle dance for yourself in this cool video.
What Attracts Bees to Flowers
Flowers have evolved to attract bees because bees assist in their pollination efforts. The shape, smell and color of the flowers all play a role in attracting bees to them.
Bees are attracted to flowers that are open and easy to access. A single row of petals and a wide open “mouth”, such as with Hosta flowers, make it easy for bees to access the nectar and pollen inside the flower. Flat flowers such as daisies or Queen Anne’s Lace are easy for bees to land on and provide easy access to the goodies bees seek.
Bees are attracted to sweet smells. This indicates a high nectar content, meaning resources to make honey. Flowers with rotten or bitter smells are less likely to attract honeybees, but they will attract other insects.
Bright-colored flowers, like clover and salvia, are also very attractive to bees. In general bees seem most attracted to blue, purple and yellow flowers, possibly because flowers of these colors also happen to smell sweet.
On each foraging trip, bees will only visit one type of flower. They’ll visit many of individual flowers, but only of one type. For the flowers, this provides pollination without crossing species. For the bees, this provides a dedicated mission and consistent food source.
Unfortunately, it also makes the bees single-minded and may mean they skip a better nectar source on a foraging trip, because it’s not what they’ve been visiting up to that point.
Number of Flowers Visited on a Foraging Trip
During one foraging trip a single honeybee will visit between 50 to 100 flowers, all the same species (unless there is a dearth and they’re unable to do so). To create one pound of honey, the bees must visit two million flowers.
A single hive can often produce between 60 to 100 pounds of honey per year and, depending on their location and the winter weather, the bees may need 40 to 60 pounds of honey to survive the winter. In extremely cold climates, up to 100 pounds may be eaten during the winter.
Bees and Flowers
Flowers and honey bees have evolved to need each other to survive. This relationship is perfectly coordinated by nature to ensure each entity gets what it needs to survive. This relationship, known as mutualism, exists in other places in nature as well.
Examples include the relationship between bovines and their intestinal bacteria or the fungi on tree roots, which interconnect a large family of trees and manage the nutritional needs of the group.
Bees and plants evolved together to need each other. During this process, bees developed specific adaptations to extract the pollen and nectar from flowers.
The fine hairs on bee’s legs help them pick up pollen. The tiny pollen particles cling to the hairs, making them easy to extract from flowers and preventing them from falling off during flight. The hairs also hold the pollen loosely enough that a few bits are dislodged when the bee lands on the next flower, which is the manner through which pollination occurs.
Plants “know” that nectar is a precious commodity to pollinators, but it’s also expensive for plants to make and requires a lot of energy. To protect this resource, plants hide nectar deep down inside the flower. Bees evolved to have a long proboscis which they can unfurl and reach down inside even the longest/tallest flower shapes, to extract the nectar.
Honeybees have an additional adaptation that many other pollinators do not have – pollen baskets. These pouches help honeybees carry pollen back to the hive. It is the joy of every beekeeper see see honeybees returning to the hive with large yellow orbs on their legs, bringing pollen back to the hive.
Although some pollen will be shaken off at each flower they visit and more will be picked up, these pouches help honeybees gather more pollen than their pouchless counterparts.
Each part of a flower has evolved to be appealing to pollinators like honeybees. The type of pollinator they wish to attract directly relates to the size, shape and placement of flower components.
The anther contains pollen. Bees seek this out and, to attract them, flowers place the anthers near the top. They’re usually round or oblong in shape and located on the top of the stamen. In conjunction with the filament, which produces the pollen, the anther is considered the male part of the flower.
The stigma is a portion of the female part of the flower. It’s also near the top and where pollen germinates. It works as one part of the pistil to create a mature and fertilized ovary, known as a fruit. By this definition a tomato is a fruit, even though we tend to think of it as a vegetable.
The petals are the most easily recognizable part of the flower. They are what our eyes see and often identifiable by the color. The shape and color of flower petals serve to attract bees and aid or hinder their efforts to extract pollen and nectar.
The benefits of pollination extend up and down the entire food chain and impact every species on the planet. The co-evolution of plants and bees has created a balanced and perfectly orchestrated pollination process that, when allowed to continue without interference, provides sustenance for every living thing on earth.