Comparative Floral and Pollen Micromorphology of Leonurus japonicus and L. macranthus (Lamiaceae)

Min-Kyeong Oak,Sungyu Yang,Goya Choi,Jun-Ho Song

doi:10.3390/d13110533

Min-Kyeong Oak, Sungyu Yang + Show 2 more

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https://doi.org/10.3390/d13110533

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Abstract

Floral micromorphology and pollen morphology of two Leonurus (Lamiaceae) species were examined and compared using scanning electron microscopy to evaluate the diagnostic value of these features to facilitate future studies on floral biology and taxonomy. Floral epidermal patterns were similar in both species, with the conical to central-conical epidermal cells on the adaxial side of the lower lip (corolla). Capitate, peltate, scale-like glandular, and non-glandular trichomes were distributed on the surface of the floral organs. Notably, scale-like anther glands and floral stomata were found on the anthers and abaxial side of the calyx, respectively. Pollen grains had bi-reticulate exine with angular primary lumina and rounded secondary lumina. These characteristics provide indirect evidence of a close association between plant-pollinator interactions and effective pollination. In addition, quantitative traits of pollen grains and trichome types on the adaxial side of the lip differed between the two species. These characteristics may have diagnostic and taxonomic value for the genus Leonurus and family Lamiaceae.

Highlights

Flower micromorphological characteristics are closely associated with plant–pollinator interactions [1]
Floral stomata may act in the exudation of nectar [19,20] or emission of volatile organic compounds [21,22]
Floral samples of two natural populations of L. japonicus and L. macranthus were collected in Korea (Figure 1)

Summary

Introduction

Flower micromorphological characteristics are closely associated with plant–pollinator interactions [1]. Especially glandular trichomes, are connected with plant-insect interactions. Gland-secreted secondary metabolic compounds such as aromatic compounds, essential oils or floral volatile scents act directly on the attraction of pollinators or defense against herbivory [9,10,11,12,13]. Several functions of anther glands have been reported, such as containing adherent substances to aggregate pollen grains and attach them to the pollinator body [14,15,16,17,18], being rewarded as food to the pollinator, and containing substances for defense against phytophagous insects [15]. Floral stomata may act in the exudation of nectar [19,20] or emission of volatile organic compounds [21,22]

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