The French chemist Prof. Pierre Baranger (1900 - 1971), who carried out experiments with plants (e.g. vetches), reported on this in 1959 and explained:
"My results look impossible, but they are available. I have taken every precaution. I have repeated my experiments x times. I have done thousands of analyses over the years. I have had the results verified by third parties who did not know what I was getting at. I've approached the matter in a variety of ways. I changed my experimenters. But there is nothing to shake about; we have to bow to the fact: plants know the ancient secret of the alchemists. Before our eyes they transform elements day by day." 
After having taken notice of the above quoted statements by Planck, Steiner and Dürr on the nature of atoms, such hitherto unexplainable phenomena as described by Baranger, which are in clear contradiction to the prevailing atomic theory, should no longer meet with fundamental rejection according to Palmström's motto "that what must not be cannot be”. But the prerequisite for the acceptance of these statements is a new awareness, an entry into the world of living being:
There is no dead matter – all material phenomena are made of spirit. The atoms are concentrations of the original efficacy of the divine idea in the universe: wisdom, love, fulfilment.
The transformation of atoms
Biological transmutation means no more and no less than the transformation of certain atoms into others. However, this transformation does not happen arbitrarily, but within a certain regularity, which can well be explained by the concepts and the model of conventional atomic theory, as Baranger points out. The transformation takes place through the exchange of protons. Just as atoms join together to form molecules through the exchange of electrons, biological transmutation aims to create another element through the exchange of protons. The total number of protons, neutrons and electrons always remains the same, so that the atomic energy is (largely) preserved.
An example: If you consider the amount of calcium in the shells of chicken eggs, you cannot explain with conventional chemistry the sudden appearance of calcium in the bones of chick embryos if the chickens only get small amounts of calcium from their feed, but instead a lot of mica, i.e. a silicic acid compound.
Especially the French natural scientist (engineer and government official) C.L. Kervran (1901 - 1983) devoted himself to these and other phenomena and found the transformation of atoms as the only conclusive explanation. His explanation is that silicon from the silicic acid Si(OH)4 in combination with carbon is converted into calcium :
28Si + 12C := 40Ca.
The numbers in front of the element symbol mean the rounded atomic weight. For the conversion by transmutation Kervran uses the symbol :=. This symbol for transformation does not automatically mean that an energetic equilibrium exists. The transformation can therefore be endothermic (through supplying energy) or exothermic (by a release of energy).
There have been research and discoveries in this direction already in the 19th century. In the middle of the 19th century, the German baron Albrecht von Herzeele already formulated: "It is not the soil that produces the plant, but the plant that produces the soil." Baranger also referred to Herzeele's pioneering work.
Rudolf Hauschka (1891 - 1969) also referred to Herzeele in his research and in the appendix of his own book Substanzlehre (Theory of Substances) he reproduces several of Herzeele's writings in their original wording, among others the text Zur Entstehung der unorganischen Stoffe (The Origin of Inorganic Substances) from 1876 , , 
The listed research work has been carried out by serious scientists and must not, under any circumstances, be associated with the medieval pseudoscience of the gold-makers, who also used the term transmutation. The element with the highest atomic number found so far in biological transmutation is iron (56Fe). Therefore, any thought of "biological gold-making" that may be budding must be let go immediately.
However, the conversion of carbon and fluorine into phosphorus can also be important and helpful for the agricultural sector, as it has so far been assumed that phosphorus, which is necessary for feeding mankind, is a limited resource.
With an increasing understanding of the nature of matter, we can also understand a natural way of transforming elements, as is obviously practiced by plants.
The nature of matter can be understood through:
In the beginning, there is the spirit, which emits the idea of life.
Life is the result of the spiritual impulse.
Matter is the result of life.
Rudolf Steiner puts it this way:
Matter is coagulated cosmic activity.
The key to the concrete understanding of Biological Transmutation could lie in finding access to understanding and realising the values
Unity, Wisdom and Love,
or it could be the consequence of an awakening which is formulated by the Rosicrucians as early as 1615 in their Confessio Fraternitatis R.C with the words:
“... after the world has slept off the intoxication from its poisoned and anaesthetic cup and, early in the morning, will approach the rising sun with an open heart, bared head and barefoot, happy and rejoicing.” 
 Pierre Baranger: Interview with the journal Science et Vie, 1959
 C.L. Kervran: Biologische Transmutation (Biological transmutation). Edition Fahrenheit, Volume 1. Archive Publisher Agraffe, Basel 2016
 Rudolf Hauschka: Heilmittellehre. Ein Beitrag zu einer zeitgemäßen Heilmittelerkenntnis (Remedial Science. A contribution to a contemporary understanding of remedies). Vittorio Klostermann, Ffm 2004 (86.ed., p.76)
 Albrecht von Herzeele: Vegetabilische Entstehung des Phosphor und des Schwefels (Vegetable origin of phosphorus and sulphur). Berlin, Peters 1880.
 A selection of observed phenomena which obviously can only be explained by a biological transmutation:
40Ca := 28Si + 12C 23Na := 7Li + 16O
31P := 24Mg + 7Li 31P := 12C + 19F
32S := 16O + 16O 35Cl := 16O + 19F
19F := 12C + 7Li 14N2 := 12C + 16O
56Fe := 55Mn + 1H
 J. van Rijckenborgh: The Confession of the Rosicrucian Brotherhood. Haarlem 1980, Chap. VIII
Kervran was posthumously awarded the Ig Nobel Prize in 1993.
Bernhardt P. J. O'Mara Bockris (1923-2013) was also awarded the Ig Nobel Prize in 1997 for his research on cold fusion [i.e. biological transmutation].
Bockris was a professor of chemistry who was mainly concerned with physical chemistry and especially electrochemistry. He has co-authored more than 700 scientific publications, including over 20 books. Bockris is best known for his textbooks on modern electrochemistry and as an early advocate of a hydrogen economy. He is one of the co-founders of CITCE, the forerunner of the International Society of Electrochemistry (ISE). In later years he supported work on cold fusion, for which he was heavily criticized. (wiki)
The Ig Nobel Prize ("ignoble"), sometimes referred to as the Anti-Nobel Prize, is a satirical award to honour scientific achievements that "first make people laugh, then make them think" (Wiki)