Self-repair of individual somatic cells
is an almost universal property of multicellular organisms, both plants and
animals. This ability is necessary to allow continuous replacement of cells
lost through senescence or damaged by wounding. In both lower animals and most
plants, the regeneration process can lead to the formation of new organs. In
plants particularly, various regeneration strategies have culminated in
mechanisms of vegetative propagation that either complement or even entirely
substitute sexual propagation.
Empirical knowledge of regeneration in
various plant species had accumulated over thousands of years of practical
gardening and agriculture. However, the knowledge of the cellular and
physiological mechanisms underlying these processes is relatively recent and
directly linked to the recognition of plant physiology as a new research
discipline in the mid-nineteenth century, in the development of which Central
European scientists played a prominent role.
From this group of scientists, at least
the name of Julius von Sachs (1832–1897) is probably familiar to most recent
plant physiologists. “At an early age he showed a taste for natural history,
becoming acquainted with the Breslau physiologist Jan Evangelista Purkyne ˇ...”
to quote the recent Wikipedia page. But the role of Jan Evangelista Purkyne ˇ
(1787–1869), both in the life and education of young Julius Sachs and in the
establishment of cellular physiology as a new science, was much more pronounced
(see Zˇ a ´rsky ´ 2012 for details). In general, Purkyne ˇ is best known
for his discovery of Purkinje cells in
1837, the large neurons with many branching dendrites found in the cerebellum;
for the discovery of Purkinje fibres, the fibrous tissue that conducts
electrical impulses from the atrioventricular node to all parts of the heart
ventricles in 1839; and for his discoveries of Purkinje images, reflections of
objects from structures of the eye, and the Purkinje shift, the change in the brightness
of red and blue colours as light intensity decreases gradually at dusk. He introduced
the scientific term plasma for the component of blood left when suspended cells
have been removed and protoplasma the substance found inside the cells. Purkyne
ˇ was the first to use a microtome to make wafer-thin slices of a tissue for
microscopic examination and was among the first to use an improved version of
the compound microscope.
Purkyne ˇ was born in Bohemia, then part
of the Austrian monarchy, now Czech Republic. In 1818, he graduated from the
Charles University in Prague with a degree in medicine and was appointed there
as professor of physiology. In 1839, he established the world’s first
department of physiology at the University of Breslau in Prussia (now Wrocław,
Poland) and in 1842 the world’s first official animal physiology laboratory.
He returned to Prague in 1849 to become
professor at the Charles-Ferdinand University, where he personally continued
mainly his animal studies. However, through hisstudents and assistants, he also
investigated the structure and function of both anthers and pollen grains and
strongly promoted plant physiology as a research discipline.
In 1851, Purkyne ˇ’s family living in
Prague took care of a 19-year-old student from Breslau, Julius von Sachs
(1832–1897), whose parents had recently died. Sachs entered the
Charles-Ferdinand University, became Purkyne ˇ’s assistant, and in 1856
received a degree of Doctor of Philosophy. He established himself as “Privatdozent”
of plant physiology at the same university, where he remained for 3 years,
carrying out research and lecturing to students. Here, and in the following years
in Germany at the Agricultural Academy at Poppelsdorf, now part of the University
of Bonn, he wrote the first world textbook of experimental plant physiology,
published in 1865.
Sachs played a leading role in the
development of plant physiology in the second half of the nineteenth century.
He was an extraordinary teacher and scientist and greatly influenced the
progress of botany and horticulture, not only in Central Europe but also in
Britain and America. Among other achievements, he is noted for laying the
foundation of microchemical methods. He proposed numerous methods for plant
culture and research, including hydroponics as a tool to study plant nutrition.
He described the morphological and physiological details of seed germination.
In connection with his photosynthetic studies, he described the appearance of
starch grains in plants as the first visible product of this process, and
during work on plant flowering, he indicated the role of plant growth
substances in its regulation – until then unknown. In this way, he further
elaborated the pioneering discovery of Charles Darwin (Darwin 1880) on the
“influences capable of regulating phototropic plant growth” (see also chapter
by Sku ˚pa et al., this volume).
The pioneering work of Sachs on the
study of plant growth and development was carried forward by two other well-known
Central European scientists: Gottlieb Haberlandt (1854–1945) and Bohumil Ne
ˇmec (1873–1966). To students of plant physiology, their names are mainly known
from basic textbooks which describe the starch-statolith hypothesis of gravity
perception by columella cells of plant root apices. The authorship of this
hypothesis can be assigned to either of them – or to both – since they
published it independently in two separate communications not only in the same
year (1900) but even in the same issue of Berichte der Deutschen Botanischen
Gesellschaft (Ne ˇmec 1900; Haberlandt 1900). With exception of this
coincidence, their earlier and later careers differed not only in their
research priorities but also in the methodology they applied to study the
processes of plant growth and development.
Haberlandt, later denominated worldwide
mainly as the “father of plant tissue culture” for his ideas summarised in his
publication “Kulturversuche mit isolierten Pflanzenzellen” (1902 – see also the
compendium published by Laimer and Rucker 2003), was better known in his time
as a plant physiological anatomist – the first edition of his “Physiologische
Pflanzenanatomie” appeared in 1884, followed by six further editions.
Ne ˇmec was 20 years younger than
Haberlandt and is generally less well known. Between 1892 and 1896, he studied
both zoology and botany at the Charles-Ferdinand University in Prague. In 1899,
he defended his habilitation thesis titled “Contributions to Plant Cell
Physiology and Morphology”. In 1901, Ne ˇmec laid the foundation for the new
university Institute of Plant Physiology which has, in various forms, under
different names and with only a small interruption during World War II, existed
till now. He was appointed its leader and later, in 1907, became full professor
in plant anatomy and physiology (1907).
Ne ˇmec is one of the founders of
experimental plant cytology. Much of his work was devoted to the influence of
various factors on cell division. He also studied polyploidy, plant
fertilisation, physiology of growth and irritability, tropisms, regeneration,
mycology, phytopathology, the role of trace elements and the history of botany.
Both his name and experimental work, characterised by his perfectionism,
enjoyed high esteem in the research community of the last century. After Jan
Evangelista Purkyne
ˇ, he was the only other Czech scientist to become an honorary member of the
Linnean Society of London.
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