The research presents the results of studying the dynamics of chlorophyll a and b accumulation over three growing seasons under varying weather conditions on the Southern Coast of Crimea in the leaves of three native deciduous and one introduced evergreen species of the genus Quercus L. It was found that the concentration of chlorophylls in leaf tissues depends on the hydrothermal conditions of the year. During periods of hot and dry weather, their content decreases. The highest pigment concentration was characteristic of Quercus robur, while the lowest was observed in Quercus ilex.

The study describes the state of the photosynthetic apparatus in the examined species under controlled wilting conditions at different combinations of temperature and air humidity. It was established that when the water deficit level in the tissues of deciduous Quercus species reaches 20–28%, exposure to high temperature and low air humidity leads to more significant changes in photosynthetic processes compared to lower temperature and higher humidity conditions.

Notably, the level of thermal dissipation of excitation energy increases substantially, the number of chlorophyll molecules associated with PSII reaction centers decreases, and the reoxidation processes of primary electron acceptors are disrupted. The most informative parameters of the photoinduction curve for diagnosing heat resistance and drought tolerance in Quercus species were identified.

The structure of the macrophytobenthos flora of the coastal marine area of the nature park "Cape Martyan" is characterised. Currently, the flora comprises 167 species, which is almost 40% of the total number of macrophytes known for the Black Sea. The species composition is represented by four divisions: Chlorophyta – 39 species (23.35%), Heterokontophyta – 35 (20.96%) Rhodophyta – 91 (54.49%), Tracheophyta – 2 (1.20%). The class Florideophyceae and order Ceramiales, is the most richly represented. The leading families include Rhodomelaceae, Ceramiaceae, Acrochaetiaceae, Corallinaceae, Cladophoraceae, Ulvaceae, and Chordariaceae. Together, the leading families account for half of the species composition. The average number of species per family is 3.15, and the average number of genera per family is 1.72. The most numerous genera, accounting for 21.56% of species list, are Ceramium, Cladophora, Ulva, Acrochaetium, and Polysiphonia. More than a third of the species composition includes monotypic genera. The genus coefficient is low, equal to 1.84. The flora has a pronounced marine warm-water oligosaprobic character, with short-vegetation species predominating. Its rare fraction (rare and protected species) includes 40 taxa. The systematic and ecological structures of the flora are characteristic of the hydrobotanical region of the Southern Coast of Crimea and the flora of the Black Sea. Research results indicate the significant role of the protected water area at Cape Martyan in preserving biodiversity in Crimea and the Azov-Black Sea region as a whole.

The Yalta Mountain-Forest State Nature Reserve is a specially protected natural area of federal significance, covering approximately 14,500 hectares and located on the southern macro-slope of the Crimean Mountains. The reserve spans a wide altitudinal range (from sea level to 1,320 m), includes diverse landscapesfrom coastal slopes to mountain plateaus - and is characterized by significant biological diversity. A total of 153 taxa of higher plants and 111 species of animals listed in the Red Data Books of the Russian Federation and the Republic of Crimea have been identified within its territory. Among them, 47 plant species and 44 animal species are included in the federal list, while 153 plant taxa and 106 animal taxa are included in the regional list. The presence of a significant number of red-listed species confirms the uniqueness of the area and emphasizes its key role in preserving the biodiversity of Crimea and Russia.

The paper examines and analyzes specific geobotanical descriptions of landslide relief forms 2 km north of the village of Mayak (Kerch Peninsula) formed as a result of intermittent exogenous geological processes: a beach composed of shell detritus, gravel and pebbles; a dead cliff in clayey-marly deposits; a ridge-andhummock surface of a landslide body with closed depressions; a deluvial-proluvial train that partially filled the rear depression at the head of the landslide body; an erosion trough that dissected the landslide failure wall; a fragment of a flattened old landslide failure wall preserved from erosion. Original data on the position of phytocenosis species on the gradients of environmental factors in landslide relief forms were obtained using the Pover program after processing the Ecodata database.

The prickly needle (Ruscus aculeatus) is an important element of the natural ecosystems of the Southern coast of Crimea. This species is not only well adapted to the diverse climatic, forest and soil conditions of the region, but also plays a significant role in maintaining the biological balance, diversity and aesthetic value of local natural landscapes.

The paper analyzes the range and conditions for the distribution of the needle in the South Caucasus and beyond the region. Its presence in vast geographical areas of Europe, Asia, and North Africa testifies to its great ecological plasticity and ability to develop in the thermal conditions of subtropical and temperate marine climates. This is especially important in the context of climate transformations, when many species face environmental challenges. This species exhibits a high level of stability due to its ability to develop on various types of soils: highly carbonate (up to 24%) with a heavy granulometric composition (up to 59% physical clay) and an alkaline reaction of the soil medium (pH=7.8).

Studies were conducted in the Upper and Lower Parks of the Arboretum of Nikitsky Botanical Gardens due to the accumulation of wet snow on the plantations, which fell in the period from February 16 to 17, 2025. The weather report is given according to the observations of the Nikitsky agrometeorological station.

Based on the results of the route survey of the Upper and Lower Parks curtins of the NBG’s Arboretum, a visual assessment of plantings for mechanical damage: deformation of shoots, cracks on trunks and shoots, breaking of branches and trunks. Special attention was paid to the aesthetic characteristic of plantings both individually and in landscape compositions. An assessment of restoration of damaged specimens after snow breakage was carried out.

As a result of wet snow buildup, 85 specimens of woody and shrub plants were damaged, including 72 trees and 13 shrubs. Three groves of Phyllostachys viridiglaucescens (Carrière) Rivière & C.Rivière were also damaged. Thirty-two specimens were damaged in the Upper Park and 53 in the Lower Park, not including P. viridiglaucescen groves.

The vast majority of specimens are viable, with the exception of 3 specimens affected by rot.

The damage mostly affected shoots of 2-4 orders. Shoot failures were mainly in the middle and upper third of the crown, exceptions – Cedrus deodara (Roxb. ex D.Don) G.Don, Rhaphiolepis bibas (Lour.) Galasso & Banfi and Pinus pinea L.

Considering that the quantitative composition of woody and shrubby plants of the Upper and Lower Parks of the Arboretum according to the 2015 inventory was 9202 specimens, less than 1% of the collection was affected. However, it should be taken into account that in park plantings of botanical gardens each specimen is of historical and aesthetic value.

A study of the genetic similarity of cultivars of a popular flower-ornamental object – garden chrysanthemum (Chrysanthemum × morifolium (Ramat.) Hemsl.) from the Nikitsky Botanical Gardens’ collection was conducted using microsatellite analysis. The exceptional economic importance and large number of cultivars of this crop make their identification problematic, which leads to a less effective breeding process. In the case of chrysanthemums, genotypes are almost impossible to distinguish using phenotypic methods due to the high variability of morphological characteristics, even if they belong to the same group. Considering the significant advantages of molecular genetic analysis for solving the issue of assessing the genetic similarity of cultivars, the purpose of this study was genotyping and establishing the genetic proximity of chrysanthemum cultivars, as well as conducting genetic certification of cultivars included in the register of breeding achievements of the Russian Federation. The study included 2 species (C. zawadzkii subsp. zawadzkii and C. сhanetii H.Lev.) and 23 cultivars. Genetic analysis was performed on 6 SSR loci. 42 allelic variants were identified in the studied sample. A high level of similarity in allelic composition was revealed between pairs of cultivars: 'Medea' and 'Puma White' (0.95), 'Elen' and 'Cascad’ de Orleans' (0.89), 'Admiral Alferyev' and 'Puma White' (0.88), 'Kira' and 'Medea' (0.88), 'Kira' and 'Puma White' (0.88), 'Admiral Alferyev' and 'Golden Spider' (0.86), 'Admiral Alferyev' and 'Orpheus' (0.86), 'Admiral Alferyev' and 'Kira' (0.86), 'Orpheus' and 'Puma White' (0.86). It was established that the studied cultivars of small-flowered chrysanthemums are genetically close to the species C. zawadzkii subsp. zawadzkii and C. chanetii, which are among the probable ancestral species of garden chrysanthemum. Our results demonstrated high reproducibility and informativeness of the selected SSR markers, which can be used to assess the genetic diversity and relationships between C. × morifolium cultivars.