Glandular trichomes of Robinia viscosa Vent. var. hartwigii (Koehne) Ashe (Faboideae, Fabaceae)—morphology, histochemistry and ultrastructure

Abstract

Main Conclusion Permanent glandular trichomes of Robinia viscosa var. hartwigii produce viscous secretion containing several secondary metabolites, as lipids, mucilage, flavonoids, proteins and alkaloids. Abstract Robinia viscosa var. hartwigii (Hartweg’s locust) is an ornamental tree with high apicultural value. It can be planted in urban greenery and in degraded areas. The shoots, leaves, and inflorescences of this plant are equipped with numerous persistent glandular trichomes producing sticky secretion. The distribution, origin, development, morphology, anatomy, and ultrastructure of glandular trichomes of Hartweg's locust flowers as well as the localisation and composition of their secretory products were investigated for the first time. To this end, light, scanning, and transmission electron microscopy combined with histochemical and fluorescence techniques were used. The massive glandular trichomes differing in the distribution, length, and stage of development were built of a multicellular and multiseriate stalk and a multicellular head. The secretory cells in the stalk and head had large nuclei with nucleoli, numerous chloroplasts with thylakoids and starch grains, mitochondria, endoplasmic reticulum profiles, Golgi apparatus, vesicles, and multivesicular bodies. Many vacuoles contained phenolic compounds dissolved or forming various condensed deposits. The secretion components were transported through symplast elements, and the granulocrine and eccrine modes of nectar secretion were observed. The secretion was accumulated in the subcuticular space at the trichome apex and released through a pore in the cuticle. Histochemical and fluorescence assays showed that the trichomes and secretion contained lipophilic and polyphenol compounds, polysaccharides, proteins, and alkaloids. We suggest that these metabolites may serve an important function in protection of plants against biotic stress conditions and may also be a source of phytopharmaceuticals in the future.

Metabolic flux analysis of the non-transitory starch tradeoff for lipid production in mature tobacco leaves

“…Alternatively, the synthesis of secondary metabolites in glandular trichome cells, which can be quite significant in tobacco leaves (up to 30% DW; Wagner, 1991 ), releases CO 2 that could be fixed by trichome RuBisCO specialized to refix this released CO 2 rather than atmospheric CO 2 ( Laterre et al, 2017 ). This unlabeled CO 2 could provide a portion of the unlabeled primary metabolites that contribute to the M0 isotopologues remaining after 5 h of labeling ( Supplemental Dataset 8 ) or even lead to the production of unlabeled starch granules within the trichomes ( Konarska and Łotocka, 2020 ), reflecting the increased cellular heterogeneity and secondary metabolite production in older leaves; however, such explanations for the current analysis are speculative. These alternate sources of unlabeled carbon may nonetheless be insufficient to explain the large proportion of carbon flux for unlabeled starch production relative to photosynthetic carbon fixation and thus warrant further investigation.…”

Advances in the Regulation of Epidermal Cell Development by C2H2 Zinc Finger Proteins in Plants

“…Some multicellular trichomes are able to secrete various substances, such as I, IV, VI, and VII type trichomes of tomato and the trichomes of Artemisia annua and tobacco (Karabourniotis et al, 2020;Schuurink and Tissier, 2020), whereas some lack secretory ability, such as II, III, V, and VII type trichomes of tomato (Yuan et al, 2021). Some trichomes contain glands that secrete secondary metabolites, such as nicotine or toxic substances, to drive away herbivores (Werker, 2000;Schmidt et al, 2011;Konarska and Łotocka, 2020;Pan et al, 2021). The main function of trichomes is to act as a natural defense system to protect the plant from both pests and physical damage (Tian et al, 2012;Sato et al, 2019;Andama et al, 2020).…”

Molecular Mechanisms of Plant Trichome Development

“…For example, the trichomes of cucumber ( Cucumis sativus ), tobacco ( Nicotiana tabacum ), tomato and snapdragon ( Antirrhinum majus ) are multicellular ( Yang and Ye, 2013 ; Tan et al, 2020 ; Zhang et al, 2021f ). Some multicellular trichomes are secretory and some are not ( Koudounas et al, 2015 ; Xue et al, 2019 ; Konarska and Łotocka, 2020 ).…”