While farmers have been cross-pollinating plants to produce hybrid varieties since 5,000 B.C., the question regarding the origin of plant sex cells has never been answered. However, Stanford researchers have solved the mystery of plant sex cells, according to a University report.

Through a series of simple experiments, Stanford biology professor Virginia Walbot and graduate student Timothy Kelliher showed that plants only require low oxygen levels to begin sex cell formation.

The two researchers first tested their theory by probing into the immature anther tissue of corn, where they found unusually low oxygen levels right when cells within began turning into sex cells. To see if low oxygen levels were indeed responsible for sex cell formation, Walbot and Kelliher introduced various gases of different concentrations and observed the results.

A high concentration of oxygen led to a drastic decrease in sex cells, while a high concentration of nitrogen gas, which provided an environment without oxidation, led to increased sex cell formation.

This is because once oxygen levels drop under a certain point, an enzyme called MSCA1, which is necessary for cells to grow into sex cells, increases its activity, leading to sex cell formation. Further experiments even demonstrated that low oxygen levels could cause cells that don’t normally develop into sex cells to do so.

— Klaire Tan