MORPHOLOGICAL AND ANATOMICAL STUDIES POPULATION OF EUPHORBIA PARALIAS L. ON A PSAMMOPHYTIC HABITAT IN THE SOUTH OF THE KERCH PENINSULA
Authors: Vakhrusheva L. P. , Petrishina N. N. , Pavshenko D. A. 
Published: August 2020

Euphorbia paralias L. is a poorly studied species that is protected by Red books at the Federal and regional levels, where its conservation status is assessed as «vulnerable» and «declining in number». Euphorbia paralias L has not been studied in terms of population structure, and anatomical studies of the species are not sufficient.The goal is to study the morphological criteria of age states, the spatial and age structure of the coenopulation, and the anatomical structure of vegetative organs.

We studied the cоenopopulation on the sandy coast in the South of the Kerch Peninsula (an embankment between the Black sea and Tobechik lake). The phytocoenosis in which Euphorbia paralias L. is few species it contains 11 species per 100 m2. The projective cover of the herbage varies from 40 to 50 %, with Euphorbia paralias L. accounting for 20 to 30 %. The average distance between generative individuals reaches 32.70±0.12 cm; between vegetative individuals – almost 3 times less than 11.40±0.26 cm. The Clark-Evans coefficients between plants were R=10.40; separately for generative plants R=24.25 and for pregenerative individuals R=0.26. Consequently, the spatial structure of the population is contagious, but in the pregenerative phase of development the species forms loci has regulary spaced distribution of individuals. Additionally, the calculated Odum index was equal to 3.03, which confirmed the contagious (clumped distribution) type of growth of individuals in the studied population.

In the laboratory, seedlings and juvenile individuals were studied, and the transition to the immature age phase was recorded. Immature, virginal, and generative plants were studied in the natural population. Morphological features for each age state are determined (Fig. 1, 2, 3). The features selected for differentiation of age states showed the reliability of differences at the level of significance p<0.05 and p<0.01 (Tab.1).

Their quantitative participation in the population was determined based on the identified morphological features characteristic of plants of different ages. In total 556 specimens of Euphorbia paralias L. were found on the studied area, including 56 juvenile specimens, 31 immature specimens, and 44 virginal specimens. 425 plants are generative (g1=75; g2=250; g3=100). The age spectrum, compiled in accordance with the classical approach (Uranov, 1975; Rabotnov, 1950), is incomplete: seedlings and plants of senile age were not found; the young part of the population is quite large and makes up 23.6 % of the total number of individuals. However, the spectrum is clearly dominated by individuals of Mature generative age, and most of all-a group of generative plants, so the spectrum is clearly monomodal (Fig. 4.). Additionally, this population was evaluated according to the «Delta-omega» classification [Zhukova, 1967; Zhivotovsky, 2001]. The following values were obtained during the calculations: ∆=0.35, ω=0.86. Thus, according to the «Delta-omega» classification, the studied population also belongs to the Mature group.

Anatomical study of vegetative organs was carried out. The obtained data on the anatomy of vegetative organs are shown in Fig. 5, 6, 7, 8, 9,10. For Euphorbia paralias, the presence of terpenoid – containing structures represented by one of the forms of receptacles with intracellular accumulation of secretions: non-segmented milkers (Fig. 9, Fig. 11). Non- segmented milkers found in the root and stem are confined to the primary cortex. In the leaf, non-segmented milkers are found in leaf mesophyll and in the subepidermal layer.

The new population of Euphorbia paralias L., found on the Kerch Peninsula in 2012, has a high number: 556 individuals grow on the studies area (100 m2), and 11.0±1.2 individuals per 1 m2.
The spatial structure of the population is contagious (clumped distribution), which is confirmed by coefficients of the Clark Evans (R=10.40) and Odum (3.03), but in the pregenerative phase the species forms loci with a regulary spaced distribution of individuals (R=0.26).
In the anatomical structure of the leaf can be traced: the appearance of a leaf blade similar to the erikoid type, in the process of its ontogenetic metamorphosis; developed cuticle, thickened outer walls of the epidermis, submerged stomata, a high index of the palisade coefficient (81 %,), the presence non-segmented milkers with latex.
Complex of xeromorphic features of the leaf, taking into account ecomorph to soil salinity (salt residue 0.1 %), in our opinion, can be attributed Euphorbia paralias to haloxerophytes ecological group.
The work was carried out within the framework of the PIT project «Development of a network educational program in the direction of training 06.06.01 Biological Sciences, orientation 03.02.08 Ecology» of the development Program of the Federal state educational INSTITUTION «KFU. V. I. Vernadsky».