A scientific approach to solving the question of ‘what is inherited and how’. Experiments with peas

When Mendel planned his experiments with peas, he first studied the conclusions of his predecessors, who had undertaken similar experiments with plant crosses. He was aware that this would be a difficult task; as he wrote in the introduction to his work however, it seems to be the only right way that can finally lead us to address an issue that is of great importance for the development of organic forms”.

20 Jun 2022 Jiřina Relichová Kateřina Radová Zuzana Jayasundera Leoš Verner

He prepared carefully for the planned experiment, and it was no coincidence that he chose peas as he was well aware of their advantages. He then spent two years preparing, checking and selecting suitable varieties. Mendel had set himself a great task and systematically proceeded to solve it; he posed hypotheses and then verified them with extensive experiments and he recorded everything carefully without missing a detail. The results confirmed his assumptions. Nevertheless, he made further trials and, as he himself wrote there was almost no doubt about the favourable result, the next generation would confirm the final decision…even with this experiment, the presumed opinion is sufficiently confirmed”. His experiments with peas were extensive and, with preparation of material, lasted 10 years. It has been estimated that he evaluated more than 27 thousand plants in all. In 1865, he presented the results of his experiments at two meetings of the Natural Science Association in Brno, and published them in the association’s yearbook.

Mendel was not satisfied with the experiments on peas, however, and went on to verify the results on other plants. In his work, he elaborates and honestly describes the results of his experiments on bean crossing; for one species he writes that the success of this experiment was negligible and that remarkable changes in the colours of flowers and seeds of hybrids occurred, but he immediately offered a hypothesis that would clarify the results (among others, ‘multigene determinations’ appears very likely from today’s point of view). Again, however, he adds honestly that the explanation is based on mere conjecture”. Nevertheless, he did not doubt the validity of his experiments, as can be seen when he wrote: No one will want to seriously claim that the development of a plant in the wild is governed by laws other than the garden bed”. Mendel was a brilliant researcher and his work Experiments with Plant Hybrids’ still stands as a good example of a scientific treatise today. To draw general conclusions from his extensive experiments was both ingenious and admirable, and it is clear that he worked intensively over a long period in solving the essence of heredity, constantly thinking about it and continuing to prove partial hypotheses. In doing so, he used all his knowledge, whether of botany, mathematics or physics.

In his book on G. J. Mendel, V. Orel literally states we can hardly imagine a researcher who, six days a week, teaches up to a hundred students in one class, performs the duties of a priest and, at the same time, conducts demanding experiments. Behind the monastery walls, he focused on researching a scientific problem that he knew was of extraordinary importance to science and practice. That was the driving force behind his great workload”.

Though no one understood the nature and significance of his cross-breeding experiments, and his work remained relatively unnoticed, Mendel carried on addressing the problem of fertilisation until his death, despite having little time to do so in his later years. He was convinced that the results of his work on heredity were correct, that they were of general application and would be recognised. At the end of his work, he writes only experiments must decide whether variable hybrids of other plant species behave exactly the same; for the time being, perhaps we can assume that no fundamental difference can be made on important points, because the plan for the development of organic life is beyond discussion”.

Consequently, we can say that the great task Mendel set as his mission was clarification of the laws of inheritance, and that he did everything in his power (or even more) to complete this mission. A year before his death, he said my scientific work has given me a great deal of satisfaction and I am convinced that it will soon be recognised by the whole world”. His passion for scientific work lasted a lifetime. Even when he had to take on the demanding functions of abbot, he continued to devote himself to his love – learning about nature. In a letter to the renowned botanist Professor Nägeli, he confided shortly after his election as abbot in 1868: there has been an unexpected change in my circumstances in recent times, as, on March 30, the chapter of the monastery elected my humble self as abbot, a position I will hold for life. From my humble position as a teacher of experimental physics, I am suddenly transferred to an area where many seem foreign to me and it will still take some time and effort before I can feel at home here. However, this does not deter me from continuing the cross-breeding attempts that have become so dear to me, and I even hope that I will be able to devote more time and attention to them as soon as I become more confident in my new position”.

He also devoted himself to his meteorological observations, the breeding and crossing of bees and the breeding of fruit tree just as thoroughly as he did crossing plants, with the intention of introducing the latest knowledge in these subjects too. He carefully and tirelessly collected all sorts of data and drew general conclusions from them. Here, too, he applied an analytical way of thinking and a sense of detail and precision in his work.


Translation: Kevin F. Roche
Editor: Zuzana Jayasundera


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