PLANT MORPHOLOGY - T. A. Sautkina - 2012

CHAPTER 7. THE FLOWER AS A SPECIAL REPRODUCTIVE ORGAN OF ANGIOSPERMS

7.1. Evolution of Concepts Regarding the Flower

The flower (from Lat. flos, Gr. anthos) is the reproductive organ of flowering, or angiosperm, plants. The Development of METABOLISM/2.html">THE CONCEPT OF the flower as a reproductive organ in angiosperms is generally associated with the name of J. W. Goethe, who published his work "Metamorphosis of Plants" (Versuch die Metamorphose der Pflanzen zu erklären, 1790). It was in this work that J. W. Goethe first suggested that all floral elements are nothing other than metamorphosed leaves of a vegetative SHOOT. This hypothesis should be regarded as the first attempt to elucidate the morphological nature of floral parts. Goethe's idea concerning the foliar Water/144.html">Origin of the flower (from Lat. folium – leaf) was supported by A. P. de Candolle, and for many years botanists viewed the flower as a vegetative shoot with a heavily shortened axis.

In the second half of the 19th and early 20th centuries, under The Influence of C. Darwin's ideas, many botanists (Ph. Van Tieghem, 1891; A. N. Beketov, 1897; A. Kerner, 1902; N. A. Bush, 1924; N. I. Kuznetsov, 1936; V. L. Komarov, 1941) reinterpreted the initial understanding of the flower's nature to some extent. Expanding upon Goethe's foliar theory, they began to consider the flower as a modified (metamorphosed) vegetative shoot. This view was supported by similarities that botanists discovered in the Ontogenetic development of the flower and the vegetative shoot, as well as between sporophylls and leaves.

This concept regarding the morphological nature of floral elements took shape gradually and remained predominant until the 1940s. The Scope of the term "flower" was also not defined immediately. The term Anthophyta (from Gr. anthos – flower, phyton – plant) – "flowering plants" – was first introduced by the Director of the Berlin Botanical Garden, Professor A. Braun (1805–1877), to designate both gymnosperms and angiosperms. A. Braun referred to the reproductive Organs of both groups as flowers. The prominent Austrian botanist R. Wettstein held a similar view regarding the scope of the Concept of the "flower." Meanwhile, many other botanists interpreted this concept much more broadly.

For instance, the German botanists G. Hallier (1868–1932) and A. Engler (1844–1930) believed that one could also speak of a flower in ferns if their fertile fronds were grouped together like those of the ostrich fern (Matteuccia struthiopteris). It was only from 1907 onwards, following a proposal by the English palaeobotanists E. Arber and J. Parkin, that the term "flowering plants" began to be applied exclusively to angiosperms, and the flower came to be regarded as a specialized reproductive organ of angiosperm plants.

The flower is the site of all processes associated with the reproduction of angiosperm plants: The formation of microspores and megaspores, spore "germination" and the Development of the male (pollen) and female (embryo sac) gametophytes, the formation of male (sperm Cells) and female (egg cells) Gametes, double Fertilization, the Formation of the zygote and endosperm, the development of the seed containing the embryo—the rudiment of the new sporophyte—and nutrient reserves, as well as fruit formation.

Thanks to thorough investigations of all the aforementioned processes conducted by botanists from various countries, since the 1940s plant Morphology has firmly established the view that one part of the floral elements results from the metamorphosis of vegetative leaves, while another part is formed through the metamorphosis of sporophylls (spore-bearing leaves).

Thus, taking into account the morphological nature of floral elements and their functional characteristics, the concept of the "flower" can be defined as follows: "A flower is a shortened, determinate, metamorphosed, spore-bearing shoot adapted for reproduction."