Plants case study: Muriel Wheldale Onslow and the snapdragon
This plant biochemist worked with botanists, geneticists and biochemists to research patterns of inheritance and plant pigmentation
In 1900, Muriel Wheldale achieved first-class honours in natural sciences at the University of Cambridge. It would be nearly 50 years before she was granted formal degree status, as the university withheld bachelor’s degrees from women until a policy change in the late 1940s. By then, though, she had died.
But in the meantime, she made major breakthroughs in the fields of botany, genetics and biochemistry with her studies of plant inheritance and plant pigments.
Botany and genetics
Wheldale’s original specialisation was in botany, which she applied from 1903 in the genetic research team of William Bateson, the man who devised the term “genetics”. He was more open-minded about the place of female scientists, allocating almost half of his highly competitive research positions to women.
Bateson was an expert on the work of founding geneticist Gregor Mendel, which was consequently of great relevance to Wheldale’s early research. When Mendel’s research on pea plants was rediscovered in 1900, a global wave of investigations was sparked into his hypotheses on dominant–recessive inheritance patterns and segregation and assortment of alleles at meiosis. One of the first phenomena to be analysed using these principles was the hereditary pigmentation of flowers.
Wheldale’s specific focus was colour inheritance in Antirrhinum (a genus of plants commonly known as snapdragons), on which she published a highly complex account of her independent research in 1907.
She worked out that there was a pattern to which snapdragons exhibited which colours – white, yellow, ivory, crimson or magenta. She based the calculation on a Mendelian approach, assuming that there were four genetic “factors” for colourisation – Y, I, L and T. In her 1907 paper, she described their roles as such: ‘‘The factor I modifies yellow, giving ivory. The factor L, superposed upon ivory, gives magenta; with yellow it blends, giving crimson; finally the third factor T is not manifested unless L in addition is present.” She also hypothesised that the original, undomesticated Antirrhinum had been magenta, as crosses of crimson, ivory or yellow with white often resulted in a “reversion” to magenta.
Furthermore, her analysis revealed and identified epistatic relationships (when one gene locus masks or modifies the phenotype of a second gene locus) in her sample cells. She termed a gene that had undergone an epistasis event a hypostatic gene. Despite this being a significant new discovery, she decided not to introduce the terms ‘epistatic’ and ‘hypostatic’ in her 1907 paper due to conflict over the precise terminology. Bateman later presented them in his work, which meant at the time he was credited with the breakthrough.
In her 1916 monograph The Anthocyanin Pigments of Plants, Wheldale aptly described her work as “On one hand… methods for the isolation, analyses and determination of the constitutional formula of [snapdragon] pigments. On the other hand… Mendelian methods for determining the laws of their inheritance”.
It was this innovative combination of techniques that allowed her to apply mechanistic approaches to the Mendelian mathematical models, as she studied the link between specific genes and the biochemical processes they initiated. She advocated this interdisciplinary approach as she believed cooperation between fields would increase the speed at which progress could be made.
Wheldale favoured the biochemistry aspect to her research over the genetics, so she departed Bateson’s team and joined the Cambridge research group of biochemist Frederick Gowland Hopkins in 1915. Like Bateson, Hopkins was unusually welcoming to female scientists given the prevailing sexism in academia; there were practically no other female researchers in any other Cambridge department at the time.
It was also observed by historian Margaret Rossiter that women seemed to be often particularly drawn to newly emerging scientific fields (such as biochemistry in Wheldale’s time), perhaps because it was seen as a fresh opportunity to establish equal representation between the sexes.
Wheldale and Hopkins studied the same pigments biochemically as she had done genetically with Bateson. A successful outflow of biochemical research was produced, resulting in a complete revision of The Anthocyanin Pigments of Plants.
In 1916, she was introduced to Huia Onslow, a fellow chemical geneticist, who was conducting independent research in a homemade lab even though he was paralysed from the waist down. For their first meeting, they shared tea and discussed the work of Mendel. In the next few years, they worked together on research into topics such as the iridescence of insects (though she was not always credited). Their professional relationship developed into a marital one, which lasted from 1919 to Onslow’s death in 1922.
In her later life, Wheldale Onslow devoted more time to education, both in teaching and writing. In 1926, she became a university lecturer, being one of the first women to hold this position at Cambridge. She published further material on plant biochemistry, but she died in 1932 before completing the second volume of Principles of Plant Biochemistry.Lead image:
Forest and Kim Starr/Flickr CC BY