Kono Yasui

How did Dr. Yasui's work make a difference?

Kono Yasui (back, second from right) with some of her students at the Tokyo Women's Higher Normal School (1949).

Kono Yasui's studies contributed substantially to our understanding of plant evolution. She herself was conscious of this connection and coupled her study of coal with investigations into plants' genetic mechanism and mutations.

Plants can be divided broadly into those with flowers, which propagate by seeds, and those without flowers, which propagate by spores. Seed-forming plants can be further divided into angiosperms, whose seeds are encased in ovaries with tough walls (most flowering plants and deciduous trees), and gymnosperms, whose seeds are not thus enclosed (pines, cypress, and other conifers, as well as ginkgo trees). Non-seed-forming plants can be classified as ferns, mosses, or algae (including various seaweeds).

These different plant groups did not all appear at the same time. Terrestrial ferns branched off from primitive algae in the Carboniferous Period (367 million to 289 million years ago), and the plant-eating dinosaurs of the Cretaceous Period (143 million to 65 million years ago) are thought to have lived on ferns and such gymnosperms as ginkgoes and cycads. The fossils of angiosperms have been found in strata from the late Triassic Period (247 million to 212 million years ago) and are thought to have divided into two lineages around the middle of that period, but they did not come to dominate terrestrial plant life until around the end of the Cretaceous.

By observing plants in each group and categorizing them, we can learn a great deal about how they evolved. Even while continuing with her research on coal, Kono Yasui carefully observed such present-day plants as morning glories, poppies, corn, and moss rose under the microscope to see how their cells divided and determine the number and shape in an effort to trace their lineages. She also studied the mechanism of heredity, whereby each plant passes its traits to the next generation, and she carefully studied apparent changes in the chromosomes of mutated spiderwort growing in Hiroshima in the wake of the atomic bombing at the end of World War II.

Today, researchers from all over the world are involved in sequencing and analyzing the genomes of such plant species as rice and Arabidopsis thaliana. In this way they are better able to compare the genes of various plants to determine their evolutionary relationship to one another. Kono Yasui's work, however, was done before anyone even knew of the existence of genes. Nonetheless, she was able to make a significant contribution to our knowledge of the mechanism of genetics and the process of evolution by her meticulous observation and analysis of changes in plant chromosomes.