The role of catalase in resistance to boron toxicity after melatonin application (MEL) was investigated in Arabidopsis thaliana plants. Col-0 and cat2-2 plants were exposed to 50 μM MEL followed by boron toxicity (BT) in a medium containing 10 mM H ₃BO ₃. Pigment loss and accordingly chlorosis were reduced by melatonin under BT conditions, while they were more prominent in cat2-2 mutants. Moreover, TBARS and H ₂O ₂ contents, which increased due to BT, decreased as a result of melatonin application and the levels of these parameters in cat2-2 mutants were higher than the values in Col-0. Antioxidant enzyme activity of SOD and SOD1 gen transcript were induced by MEL under BT. Conversely, APX4, PER10 and CAT1 transcripts were down-regulated by MEL under BT. In addition, antioxidant enzyme activities and their transcript levels were lower than those of Col-0. Thus, we suggested that MEL scavenged ROS directly under BT. Melatonin also reduced the accumulation of boric acid in leaf tissues of Col-0, but not cat2-2. Finally, even though melatonin application provided a degree of endurance, the cat2 mutation resulted in increased sensitivity to BT.

Conifers are long-lived species that cope with multiple abiotic and biotic stresses. To defend themselves, they have evolved a wide array of morphological, anatomical and chemical traits. Morpho-anatomical traits of Juniperus seravschanica, particularly in male and female cones, have not been studied. Thus, in this survey, these structures were studied to investigate the adaptative traits. The species is frost- and drought-tolerant and grows at a 2200-3800 m altitude on normal, chalky, calcareous, rocky, and mountainous outcrops with other species or as pure patches. The seedlings and young plant leaves were small and needle-like, while the main leaves of adult plants were scale-like and overlapping; there was a conspicuous resin gland (duct) in the outer surface of scale-like leaves secreting a white and sticky resinous substance, particularly in damaged leaves. The epidermis was thick with thicker outer walls and sunken stomata; the hypodermis showed 1-3 layers of lignified cells with a narrow lumen. The palisade parenchyma was observed on both sides. Sclereids, phenolic- and starchy cells were observed in leaves, particularly scale-like ones. Male cones were small with overlapping and decussate scales, in which resin glands (ducts) and phenolic cells were also observed. Similarly, female cones had overlapping and decussate scales converting to fleshy, berry-like, and bluish appearance during development. They revealed the presence of several resin glands, a thick epidermis, phenolic cells in young cones, and numerous sclereid cells in mature cones. Tracheids were narrow in leaves and cones. The features such as high sclerophylly, resin glands, phenolic cells, narrow tracheids, sunken stomata, increasing thickness of the epidermis, cuticle, hypodermis, as well as the presence of palisade parenchyma on both sides enable the species to survive in hard conditions.

Pollen morphology of Polygala taxa from the family Polygalaceae in Turkey is presented in this study. Pollen features of 18 species along with one undescribed species in the section Polygala were examined with light and scanning electron microscopy, 11 of which were studied and defined for the first time. Cluster analysis and principal components analysis were conducted to determine informative palynological characters and to discover similarities among the studied taxa. Based on qualitative and quantitative variables in the phenogram, the studied taxa were divided into three major clusters. Multivariate analyses revealed that apocolpium characters, including a psilate apocolpium, the presence of apocolpial lumens with granules and small depressions with psilate or rugulate walls are the most distinct features for discriminating Polygala taxa. Intraspecific variations in some pollen characters, such as the exine pattern and aperture membrane features, are reported for several taxa. Pollen morphological data obtained in the present study are compared with those from previous studies for a number of species, and the results are evaluated. In addition, the aperture number and its probable significance in the Turkish Polygala are considered for some taxa, with emphasis on their known pollination strategies.