Sesame: does the color matter?

Spring is such an anticipated season: the weather starts getting nice, we can enjoy more daylight, the sounds from birds become notorious, and life becomes more colorful in general. Other than pollen allergies, Nature provides us with flowers and animals in an outstanding range of colors. No wonder spring has served as inspiration for many artists.

Not all plant species are suitable for honey bee pollination. Some plants have flowers that have evolved to attract a specific group of pollinators. Many of the pollinators are insects: bees, flies, beetles, butterflies, moths, etc., but bats and birds, like hummingbirds, also do a great job pollinating.

Sesame is an oil seed crop that attracts different insect pollinators. However, it can self-pollinate. In other words, pollen can get from the flower’s male structures to the flower’s female structures of the same plant without the need of a pollinator. So, why do sesame flowers attract pollinators if they can self-pollinate?

Even though sesame and other plants can self-pollinate, self-pollination doesn’t yield the same results as cross-pollination. With cross-pollination, plants can have better seed production and seed quality. The fact that self-pollination happens with flowers of the same plant has a very limiting effect on genetic variation. Cross-pollination is what ultimately allows for the processes of evolution to happen and for new varieties to appear. Cross-pollination can also lead to an earlier harvesting time.

Do pollinators have a preference in terms of what plants they pollinate? They might. Nectar and pollen from different flowers can vary in nutrient content, and there could be other environmental factors that affect which plants get pollinated. A study in Egypt, in the region of Fayoum, looked at pollen collection by honey bees for 2 years, and found that the pollen came from 24 different plant species, most of it coming from sesame and maize.  

Both sesame and honey bees get great benefits from their mutualistic relationship. And as consumers, we get to enjoy the end result. Time to have some tahini!

Interesting fact: Sesame flowers are visited by insect pollinators most frequently between 11am and 1pm, and then between 1pm and 3pm. That’s when the flow of nectar is at its highest in sesame plants.

References:

Agidew, M. G., Dubale, A. A., Atlabachew, M., & Abebe, W. (2021). Fatty acid composition, total phenolic contents and antioxidant activity of white and black sesame seed varieties from different localities of Ethiopia. Chemical and Biological Technologies in Agriculture, 8, 1-10.

Andargie, M.; Vinas, M.; Rathgeb, A.; Möller, E.; Karlovsky, P. Lignans of Sesame (Sesamum indicum L.): A Comprehensive Review. Molecules 2021, 26, 883.

Degefa, F. T. (2019). Review on sesame (Sesamum indicum L.) breeding in Ethiopia. J Biol Agric Health, 9(17), 39-45.

Zhou, L., Lin, X., Abbasi, A. M., & Zheng, B. (2016). Phytochemical contents and antioxidant and antiproliferative activities of selected black and white sesame seeds. BioMed research international.