Klement Timiryazev's contribution to plant nutrition theory and plant physiology

A special merit in the development of the theory of carbon plant nutrition belongs to the Russian scientist Kliment Arkadyevich Timiryazev (1843–1920). He studied the dependence of photosynthesis on the qualitative composition of light; he established that photosynthesis is carried out in strict accordance with the law of conservation of energy: sunlight energy is absorbed by chlorophyll and used for the formation of organic substances from carbon dioxide and water. "Plants," wrote the scientist, "are the mediator between heaven and earth. They are the true Prometheus who stole fire from heaven. The sunbeam stolen by them burns in the flickering splinter and in the blinding spark of electricity. A sunbeam sets in motion the monstrous mechanism of a giant steam engine, the artist's brush, and the poet's pen." K.A. Timiryazev was the first to show that the green color of chlorophyll is an adaptation for the absorption of solar energy, and that the maximum light absorption by chlorophyll occurs in the red region of the spectrum. By applying precise methods of physics and chemistry to the physiology of plant nutrition, he made a significant impact on the development of the fundamental principles of agronomic science through his work.

In 1867, K.A. Timiryazev took part in conducting the first agronomic experiments in Russia, organized by the Free Economic Society.

Chlorophyll (from Greek for green and leaf) is a green pigment of plants contained in chloroplasts. The name was proposed in 1818 by French scientists P. Pelletier and J. Caventou.

Under the guidance of Professor D.I. Mendeleev, he set up field experiments to clarify the influence of mineral fertilizers on rye and oats. On the basis of these and subsequent scientific experiments, the scientist formulated a number of theoretical propositions regarding water regime, mineral nutrition, and other issues of plant life. Kliment Arkadyevich considered the task of a botanist-physiologist to be not only describing and explaining the phenomena of plant life but also managing the processes of their vital activity. One of the main principles of K.A. Timiryazev's work was the study of plant physiology in relation to agriculture. He considered it expedient to breed cultivars with a powerfully developed root system or reduced transpiration; he substantiated the possibility of reducing unproductive water expenditure by plants through the use of fertilizers; he pointed out the need to use the vegetation method in agriculture and to build chemical plants for the production of saltpeter; he predicted the industrial significance of growing plants under artificial electric lighting. K.A. Timiryazev highly valued the scientific principles of one of the founders of agrochemistry, J. Liebig, especially regarding the return to the soil of nutrients removed with the harvest that are deficient in it. In his work "Agriculture and Plant Physiology," he wrote very vividly and accessibly about the theory of mineral nutrition of plants by J. Liebig. Speaking about ash elements, Kliment Arkadyevich emphasized: "Once extracted from the soil, they will not return by themselves; they can be returned only by the same force that extracted them, i.e., man. Hence, ash extracted by any plant – whether cereal or legume – is the soil's impaired capital, which must be reimbursed in one way or another if we wish to hand over the land to descendants as we received it from our ancestors. This is the famous 'law of return,' proclaimed by J. Liebig, and representing, no matter how much one tries to limit its significance, one of the greatest acquisitions of science." He considered the expansion of sowing grain legumes to be one of the most important ways to increase field productivity. K.A. Timiryazev highly appreciated the discovery of symbiotic nitrogen fixation by grain legumes, which he highlighted as "one of the brilliant recent acquisitions of the doctrine of plant nutrition." He was the first in Russia to begin research on the physiological role of trace elements in the life of plants. This is evidenced by the results of his experiments on studying the effect of iron, nickel, manganese, cobalt, and zinc on the conversion of phylloxanthin into chlorophyllin.

In 1872, Kliment Arkadyevich was the first to pay attention to the elimination of chlorosis in plants by spraying leaves with aqueous solutions of zinc. On behalf of the Ministry of Agriculture in 1896, K.A. Timiryazev set up an experimental station at the All-Russian Exhibition in Nizhny Novgorod. According to his plan, a greenhouse for vegetation experiments was built, equipped with the necessary apparatus and instruments. In addition, in a greenhouse, he set up small-plot field experiments, where he demonstrated experiments on plant nutrition accessible to the general public. All this served as a prerequisite for the development of agrochemistry in Russia. Here it is appropriate to quote the words of K.A. Timiryazev himself: "Looking back at the path traveled, I,... think I can say in good conscience that I did what I could to ensure success for them (scientific ideas. – Auth.). I investigated the issue from all available sides... improving the methods of research and using for its explanation every new success in related fields of chemistry and physics. Not leaving the soil of direct experience for a minute... I limited myself only to the role of a witness, stating facts and remembering the duty... to tell 'the truth, the whole truth, and nothing but the truth'."