My favorite gardener

I understand it’s gardening season, and in honor of that fact, (though I personally avoid gardening as being too much like work), I’d like to introduce you to my favorite gardener of all time: an Augustinian monk named Gregor Mendel.

Gregor Mendel was born Johann Mendel on July 22, 1822, in what is now the Czech Republic. His parish priest and the local teacher helped him get secondary schooling, unusual for the son of peasant farmers, but after his father was injured in 1838, he was chronically short of money and it looked like he’d have to drop out of college.

One of his professors suggested that instead he join the Augustinians, whose main work was teaching, because then the order would pay for his schooling. In 1843 Mendel joined the Abbey of St. Thomas in the town of Brünn (now Brno) and took Gregor as his new name.

St. Thomas boasted scientific instruments, an excellent botanical collection, an extensive library–and an abbot, C. F. Napp, who shared a love of plants with Mendel. Abbot Napp made it possible for Mendel to study at the University of Vienna from 1851 to 1853, where his courses ranged from plant physiology to experimental physics, and the importance of both solid scientific experimentation and mathematics were emphasized.

When Mendel returned to the Abbey, Abbot Napp allowed him to make use of a portion of the abbey’s garden and greenhouse as he liked. Mendel set out to apply the rigorous scientific methods of physics to the problem of heredity.

Mendel knew that when you crossed plants with different characteristics, the resultant hybrids sometimes showed the characteristics of both parents–but not always. Sometimes traits would seem to disappear, only to reappear in later generations. Mendel decided to search for a pattern.

He worked with common garden peas because they had large flowers and a wide range of variations he could map. As well, they are self-fertile and breed true: an individual plant’s offspring will closely resemble it unless the plant is fertilized with pollen from another plant.

Mendel focused on seven characteristics: seed shape and color, seed coat color, pod shape and color, flower position and stem length. Over eight years he grew and studied almost 30,000 pea plants, following some through seven generations. He mated plants that differed in particular characteristics, then counted the number of offspring that showed each form of the characteristic he was testing. Then he let the hybrids and their offspring fertilize themselves. Then he mathematically analyzed the results.

Patterns emerged. Crossing tall plants with short ones, for example, always produced tall plants. If the hybrid tall plants were allowed to self-fertilize, however, the next generation had about one short plant in every four. In the next generation after that–and in more generations after that–the short plants always produced more short plants, one-third of the tall plants produced only tall plants, and the remaining two-thirds of the plants produced both tall and short plants, in that same ratio of three to one.

This pattern held true with each of the seven traits. Based on his results, Mendel formulated four rules: 1) Traits were passed as unmodified “factors” to successive generations in set ratios. 2) Each plant contained two factors, one from the egg and one from the sperm, that specified the form of each trait. 3) Each parent’s pair of factors therefore had to separate during the forming of the sex cells, so that each sex cell only contained one factor. 4) Chance determined which combination of factors each offspring received.

Mendel called the more common trait dominant, and the other recessive. When both were present, an individual plant would take on the characteristic of the dominant factor–but the recessive factor wasn’t destroyed, and would still show up in later generations whenever chance produced a plant with two copies of it. Mendel also discovered that each trait he studied was independent of the others.

Mendel’s resulting paper, “Experiments in Plant Hybridization,” was published in 1865 in a minor journal–and went essentially unnoticed until 1900 when researchers, Hugo de Vries, Erich Tschermak von Seysenegg and Karl Correns independently rediscovered Mendel’s work and laws. Mendel, alas, didn’t live to see his work rediscovered. He died in 1884.

Today, Mendel’s “factors” are called genes, and the study of them is called genetics.

And that’s why he’s my favorite gardener. He didn’t just grow peas: he grew a whole new branch of science.

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