Carpological features of Lonicera L. (Caprifoliaceae Juss.) of the flora of Ukraine

Abstract

Objective – to carry out macro- and micromorphological studies of fruits and seeds of representatives of the genus Lonicera of the flora of Ukraine (both natural and introduced), to clarify their features, to provide additional characteristics and to evaluate the possibility of using carpological features for the diagnosis of taxa of the genus.
 Material and methods. Materials of the National Herbarium of the M.G. Kholodny Institute of Botany National Academy of Sciences of Ukraine (KW) and Herbarium of the M.M. Gryshko National Botanical Garden of the National Academy of Sciences of Ukraine (KWHA) were used, as well as samples from living plants of the collections of the M.M. Gryshko National Botanical Garden and O.V. Fomin Botanical Garden. The citations are given by the original text of the labels. The fruits and seeds of seven species of the genus (four are introduced and the other are species of natural flora), listed in “Vascular plants of Ukraine. A nomenclatural checklist”, have been studied. Morphological features of fruits and seeds were studied under light microscope (LM, MBS-9) and scanning electron microscope (SEM, JSM-6060 LA). Samples were sprayed with a layer of gold according to the standard method. The study was conducted at magnification from ×30 to ×3000. Descriptions of fruits and seeds were performed using terminology, summarized in specialized papers. Fruit and seed sizes were measured using Axio Vision Rel. 4.8.
 Results. The fruits of Lonicera species are free or adnate at the base, surrounded by, for the most part, free bracteoles. A pseudocarp of L. caerulea is formed of the bracteoles of paired flowers concrescent in a tubular cupule, which completely and tightly wraps free paired fruits. The L. nigra has an uneven concrescent of the bracteoles that freely surround the paired fruits, which have concrescent only at the base. The fruits of the species Lonicera are black and dark blue, or red and yellow. The fruits of subgenus Periclymenum (L. caprifolium, L. etrusca, L. periclymenum) are free and spherical . The subgenus Chamaecerasus species’ fruits are mainly spherical, but in some species the fruits are also hemispherical, elliptical and elongated (L. caerulea, L. tatarica). Fruits in this subgenus are free (L. caerulea, L. tatarica) or coalescent at the base (L. nigra, L. xylosteum). All the studied species are characterized by glabrous fruits, except fruits of L. xylosteum that are pubescent with glandular and simple hairs. The seeds are elliptical, ovoid, nearly spherical, flat, concave on one side and convex on the other side, with recess on the periphery and a crest in the center, at the base they mainly narrow-rounded. All species of the section Eucaprifolium and one species of the section Coeloxylosteum have truncated seeds. The surface of the seeds is almost similar and pitted; in L. xylosteum it is shallow-pitted, in L. nigra it is tubercular-pitted. In some species the seed surface is pitted and also flat cells are present.
 Conclusions. Based on the results of a critical review of literature materials and analysis of own data, the detailed characteristics of fruits and seeds of the representatives of the genus Lonicera L. within the flora of Ukraine have been compiled. These characteristics can be useful for more accurate identification of fruiting Lonicera plants. The species of the subgenus Periclymenum have exclusively free fruits, while the fruits in the subgenus Chamaecerasus are free or coalescent at the base. The features of color and shape of the fruits and seeds, the peculiarities of pubescence of the fruits are suggested to be used to distinguish L. caerulea, L. caprifolium, L. etrusca, L. nigra, L. periclymenum, L. tatarica and L. xylosteum. Analysis of the microstructure of the seeds surface revealed that there no features that can be used as diagnostic at the level of subsections, sections and subgenera. However, seeds microstructure showed some differences at the species level.