The Caucasian Representatives of the Genus Paeonia L.

L.M. Kemularia-Nathadse, Trudy Tiflis. Botan. Sada 1961

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Chapter II

Morphological characters of the Genus Paeonia L. and their taxonomic meaning.

As a peculiar feature of any species of the genus Paeonia L., not only the structure of Genustive and vegetative systems comes to be essential, but also the peculiarities of its vital forms. The genus comprises large perennial plants mostly; less frequently shrubby species are available, and no annuals are availed at all.

The peonies rhizomes are branchy, with spindle-like or oblong, cone-shaped radical thickening, which are upon short or long pedicels. The shoots are solitary or united in groups, yellow or reddish in early terms, pulpy. The seedlings have entire or ternate first leaves. The stems are simple or branchy, cylindrical or slightly flattened, grooved, usually high, some of them reaching 2 m in height, although some of them are met with a height 20-25 cm.

Leaves are green or glaucescent, double-triple ternately or pinnately parted into broad and large or narrow and changing from linear-lance-shaped to nearly filiform leaflets, which are smooth-edged or toothed, lobed or dissected, and some of them having ternate or even entire upper leaves.

The leaves consistence is thin in most cases, but as fruits get ripe, it becomes nearly leather-like hard. but for some species, leaves are pulpy (e.g. the North American species).

The leaf-stalks are cylindrical usually, and only at their very base they are flat.

The blossoms are solitary, large, actinomorphic, with all their parts being free (loose). The perianth (floral envelope) is double. The calyxes are unequal, variating in form and size, all of them having the foliage origin, as it is corroborated by the fact that every calyx has proximal and distal parts differing from each other. The proximal part is related with a stalked sheath or a petiole of the cauline leaf and is broader than the distal part, laminate and concave; and the calyx is formed by the proximal part as a whole. As to the distale part, it is related with a leaf blade, forming a leaf-like, terminal appendage.

The petals are homogeneous in form, size and colour, in rare cases they are slightly variegated. Their form is obovate, oval with a wedge-shaped base, or nearly rounded. Their colour is yellow, cream, milky-white, red, purple, reddish-violet, pink, in rare cases reddish-brown or white. The stamens are numerous, loose (free) with long threads which are assumed by many to be united at the base, forming a circle, which is not quite correct. The peculiar formation, to which stamens are fastened and which is known in literature as the staminodal disk, is mistaken for the above-mentioned circle.

For some peonies species the inner edges of the staminodal disk are thin, membranous-or leather-like, and being intensively developed and overgrown, they get form of a pitcher, covering the gynecium nearly completely, so that only stigmas remain uncovered (P. suffruticosa Andrews, P. montana Sims). As to other species, the above-mentioned edges are more or less pulpy., lobed, short, reaching up to one third of a gynoecium's height (the North-American and some East-Asian species), and for some species lobes are tubercle-shaped (P. Mlokosewitschii Lomak. and some other yellow-blossomed peonies of Caucasus) or their disk is nearly unseen (for the European species). The gynoecium is always apocarpous, consisted of 2-5 fleshy carpels, and in less frequent cases, by reason of underdevelopment, a carpel is solitary (P. Emodi Wall.). The ovary is naked or tomentose-downy, simple, with many ovules, ovate, oblong-ovate, lengthened-ovate, with a short style or almost sessible stigma, in less frequent cases a style is rather long (P. macrophylla Lomak.). The stigmas are fleshy, laminate, unsymmetrical, and less frequently symmetrical, always being flesh-coloured, purple, reddish-violet or pink; and usually the edges are wavy.

The fruits are naked or tomentose-downy, large, follicle-shaped, with fleshy and, after having got ripe, leather-like robust walls of a pericarp and with flesh-coloured or yellow walls of an endocarp; the fruits are oblong-ovate or round, straight or slightly spreading. The seeds are fleshy, black or bluish-black, red, wrinkled or smooth, placed at both sides of the ventral suture. The ovules have a double envelope (integumentum); moreover, the outer envelope is massive, exceeding in size the inner envelope.

The taxonomic meaning of the above-mentioned characters of the Genus Paeonia L. is estimated differently by botanists systematizers. De Candolle ascribed significance to the vital form, structure of the staminoidal disk and pubescence of leaves. The first two characters were considered by him sectional, and the second character was regarded by him to be more important than the specific characters. As it is well-known, De Candolle divided his section Paeon DC into two groups of species in accordance with the lower side of leaves being or not being downy. Form and structure of the staminoidal disk were regarded by Lynch as the characters on which base dividing of the Genus into subgenuses might be carried out, and accordingly, he divided the Genus Paeonia L. into three subgenuses (see below the chapter "Classification of the Genus Paeonia L."). A number and form of sepals, presence or absence of the terminal appendage of sepals were considered by Stern as important taxonomic features. He ascribes to these features phylogenetic purport even. Just as the more number of sepals variating in form and presence of the terminal appendage are peculiar for primitive species, so the less number of sepals, between which transmitting is more abrupt than in the previous case, is characteristic for more advanced species.

A form of the apex of an ovary and stigma is regarded to be an important taxonomic character for identifying species, subspecies and varieties, and which was used by Finet and Gangnepain for describing the East Asian species. They suppose that, a number of blossoms has phylogenetic meaning and, as a result, the species having the maximal number of blossoms upon stems are considered by them most primitive.

N. A. Busch assumed the presence or absence of pubescence upon an ovary to be an important and constant feature for identifying species. Nevertheless Stern does not ascribe any significance to this character, supposing that in some rare cases only, it may be applied to varieties. Moreover, he does not consider the vital form a sectional character and unites shrubby and perennial peonies, having well-distinguished lobes of the staminodal disk into one section. However, a form of leaf-lobes is assumed by Stern to be a subsectional character, and Komarov and Schipczinsky consider this character serial.

As far as our point of view is concerned, we suppose that -every taxonomic unit is characterized by a complex of morphological characters and, being combined in various ways, me above-mentioned characters are taxonomic, also.

But also we would like to emphasize the importance of such a character as the corolla's colour, to which, as it has been indicated by M. G. Popov (1957), botanist-systemizers don't pay proper attention, considering it inessential.

M. G. Popov (1957) carried out his researches on poppies, using results of Lowrence, obtained through genetic analysis obtained on dahlias, Burkstone and Derbshuire who worked on anthocyans.

Working on genetics of dahlias, Lowrence has proved that the appearing of pigments of flavones (yellow) and anthocyans is occurring in sequence only; just as anthocyans may develop in the presence of flavones only, so if the latters are absent, a corolla remains white.

The explorations carried out by Buckstone and Derbshire revealed that the anthocyans exist of two kinds, which are "red" and "blue". Depending on the value PH of cellular sap their colour changes. For PH 3 both of them are red , for PH 5-6, the first of them is pink, another one is lilac, for PH 9-11, the first of them becomes violet, another one gets green.

On a base of the above-mentioned explorations, M. G. Popoy_has arrived at a quite correct and important conclusion, that the anthocyans are a phylogenetic product of transforming of flavones, and as a result, the corolla's colour should be considered a phylogengtic character.

We abide by the opinion expressed by M. G. Popov and assume that our section with yellow flowers is more ancient than others

The extent to which a flower opens may be regarded as a proper taxonomic character for identifying species and, according to our observations, it depends on a petals form; just as for obovate and sharply concave petals the peonies blossoms are half-patent.

Also, such characters, as a form of Peonies ovary and fruit, presence or absence of pubescence upon them, form and colour of petals and stigmas, presence or absence of grey blue bloom upon leaves, dissection of leaves lobes, are considered by us important a taxonomic features too.

From all above-mentioned characters of the Paeonia L. genus such the features as the yellow colour of petals (resulting from flavone pigments presence), presence of the staminoidal disk in form of a pitcher, a long conical pendent fruit, absence of pubescence upon ovaries, fruits and leaves, the green colour at both sides of a leaf-blade, broad, smooth-edged leaf-lobes and the shrubby vital form are regarded by us, as the most primitive and, at the same time, ancestral characters.

Also, for the genus Paeonia L. such characters as dissection of leaf-lobes (it's well-known, that dissection of leaf-lobes results from adaptation by plants to an arid climate, because it leads to diminishing of the evaporating surface of a leaf-blade), shortened ovate or oval fruits, tomentose pubescence upon ovaries and fruits and, at last, grey-blue bloom upon leaves Have been found out by us, as more advanced.