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Celebrating Marie Clark Taylor

Marie Clark Taylor (1911-1990)

Black History Month seems like the perfect opportunity to learn about a African American woman who contributed to our knowledge of plants, the natural world and education.

Marie Clark Taylor was the first African American woman to get a PHD in Botany and the first woman to get a PHD in science from Fordham University in New York City. It is difficult to find specifics on her research, but one thing is clear - she was fascinated by how light influences plant growth. Her dissertation, “The influence of definite photoperiods upon the growth and development of initiated floral primordia,” is a deep-dive into how light influences the cells in a plant that will develop into flowers, known as floral primordia. Primordia are present in all multi-cellular organisms and are the earliest recognizable sign of organ development. In plants, primordia are the simplest group of cells that trigger organ growth such as leaf primordia which lay the foundation for new leaf formation and floral primordia which give rise to flowers. Differing amounts of light can change when a plant will shift from stem and leaf growth to flower growth. This type of light-mediated plant development is known as photomorphogenesis and it can influence plants at several life stages including germination, seedling development and the switch from vegetative growth to flower production.


An excerpt from Marie Clark Taylor’s dissertation, The influence of definite photoperiods upon the growth and development of initiated floral primordia, showing the difference in flower development between plants exposed to a 6-hour, 10-hour or 16-hour day lengths. You will notice the largest flowers of both disc and ray flowers combined where those grown with 10 hours of daylight. (source:


Although Marie focused on the effect of uninterrupted day-length, today, botanists generally accept that it is actually the length of uninterrupted darkness that triggers some of these developmental changes in plants. Still, Marie’s studies are a part of a foundation of research into photoperiodism which gives all of us gardeners, farmers and other avid plant growers the information we need to understand short-day, long-day and day-neutral plants, and how different species respond to day-length... or night-length as is happens.

You might, for instance, be fond of growing vegetables. Perhaps you want a delicious harvest of turnips this year and you live in a northern part of the U.S.A. Turnips are a long-day plant, meaning that they require more than twelve hours of uninterrupted darkness to flower. You could plant your turnips in May and then harvest them in July, but by then the day length would be over 12 hours, meaning your turnips will have initiated flower development. The last thing you want is for your turnips to send all of that energy and sweetness from the root into flower production! You would end up with rather bitter turnips. Instead, as many of you probably know, you’ll want to plant turnips either earlier in the spring or late summer. We have Marie Taylor Clark and others to thank for some of the science behind sweet versus bitter root vegetables and greens!

Not only was Marie a gifted botanist and plant physiologist though, she was also a wonderful and inspired educator. After earning her PHD and then serving in the Army Red Cross during World War II, Marie joined the faculty in the Botany Department of Howard University and later became head of the Botany Department. She also put on summer science institutes for teachers where she encouraged them to use plant materials in the classroom. She also advocated for light-microscopes in classrooms to help improve the study of living cells for all students. Her efforts in education were recognized by the National Science Foundation, which funded an expansion of her summer science institute in the 1950s and 1960s.

Throughout my research on Marie, it really struck me how little information there is about her and how relatively unknown she is in the botany world. When I searched the web for more information about her, I came across variations of the same information I’ve outlined here, but I found very little detail about her life. I’ll admit, I am a little frustrated it is so difficult to learn about her! I can imagine that as a woman and as a person of color working professionally in the mid 1900s, Marie had to overcome strong societal barriers to become the successful scientist and powerhouse educational advocate that she was.

I’ll have to leave much of Marie’s life as a mystery, but as the student who really enjoyed peering through a microscope at the cells of a thinly sliced onion during her biology labs in college, I’m left with a sense of gratitude for Marie...gratitude for the prevalence of microscopes in classrooms yes... but also that women like her helped pave the way for a woman like me to study plant science.


Clark, Marie Beatrice, "The Influence of Definite Photoperiods Upon the Growth and Development of Initiated Floral Primoridia" (1941). Accessed on 2/2/2021 from:…

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