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Anatomical and ultrastructural investigations of the glandular trichomes of aboveground organs of the white horehound ( Marrubium vulgare L.) were carried out. Additionally, identification of the main components of the secreted products was conducted. The following types of glandular structures were found: peltate with a stalk cell and a large eight-celled head and capitate trichomes, which were divided into three types: I. long-stalked with a 1-celled head, II. short-stalked with a 2-celled head, III. short-stalked capitate with a 4-celled head. Histochemical tests showed that the glands contained various substances such as lipids, polysaccharides, phenolic compounds, terpenes, tannins, and flavonoids. During the secretory stage, the ultrastructure of the bicellular head of the capitate trichome was characterized by a highly developed rough endoplasmic reticulum, numerous plastids, and mitochondria. After exocytosis, the secretion was temporarily stored in the periplasmic space and passed through the cell wall to the subcuticular space. [ABSTRACT FROM AUTHOR]

• Aesculus hippocastanum is a valuable ornamental tree present in urban greenery. • Defense strategies of Aesculus leaves against Cameraria ohridella were studied. • Increased polyphenol content was observed in infested Aesculus hippocastanum leaves. • New details of the morphology and behaviour of C. ohridella larvae were provided. • Histochemical tests, fluorescence assays, and scanning electron microscopy were used. Although Cameraria ohridella is a pest mining Aesculus hippocastanum leaves, has been known in Europe for 30 years, there is still no completely efficient method for control of this insect. The defence strategies of A. hippocastanum leaves against infestations by this pest have not been fully elucidated yet. The aim of the present study was to identify the defence strategy adopted by A. hippocastanum against the pest based on anatomical and histochemical analyses of leaves as well as to provide details of the morphology and behaviour of the developmental forms of C. ohridella. The study was carried out using a scanning, light, and fluorescence microscope. It was demonstrated that the response of the A. hippocastanum to C. ohridella larval infestations consisted in enhanced accumulation of phenolic compounds in tissues located at the border of mines and in the thickened layer of the leaf supporting the cocoon. Thorough analyses of the consecutive developmental stages of C. ohridella revealed new previously unknown features of larva L 1 and some details of the mandible structures of feeding larvae L 1 -L 4 and the characteristics of the cocoon structure, which is produced by larvae L 5 and L 6. We have found six stages in the developmental cycle of this pest in the present study. [ABSTRACT FROM AUTHOR]

• Tilia pollen can cause pollen allergy in sensitive people. • In Poland, the risk of allergy to Tilia pollen occurs in June, July, and also in May. • The highest counts of Tilia pollen occur during the T. cordata flowering period. • The acceleration in the pollen season onset was almost 14 days during 18 years. • In 2018, the annual pollen sum increased by more than three times. Lindens belong to valued trees that are frequently planted in urban green areas. Nevertheless, during their flowering they can pose a risk to sensitive people in cities due to their allergenic pollen. This paper presents the results of a 3-year phenological study (2016–2018) and an 18-year aerobiological study (2001–2018) conducted in Lublin (Poland). The flowering phenology data for the following five species: T. americana , T. cordata , T. × euchlora , T. platyphyllos , and T. tomentosa , were compared with the data regarding Tilia pollen seasons. It was shown that the largest amounts of airborne Tilia pollen grains occur during the full flowering period of T. cordata and that the flowering sequence of the linden species studied is constant during the growing season: T. platyphyllos , T. americana , T. cordata , T. × euchlora , and T. tomentosa. We found pollen seasons to start earlier by 14 days and to be extended by 15 days. Throughout the study period, the annual Tilia pollen sum did not change significantly. However, in 2018 in which there was a significant increase in temperature above the average for the previous 17 years, flowering and pollen release distinctly accelerated, and the annual pollen sum increased more than three times compared to the average for the previous 17 years. In central-eastern Poland, the risk of pollen allergy due to the presence of Tilia pollen occurs in May, June, and July. We recorded the highest linden pollen concentrations in June. Due to the acceleration of flowering and pollen release in linden trees as a result of global warming, the incidence of pollen allergy in central Europe can be expected to become more intense already in the second half of May. Therefore, linden plantings in new urban green areas should be planned to be established at some distance from residential estates. [ABSTRACT FROM AUTHOR]