The Morphological and Anatomical Traits of the Leaf in Representative Vinca Species Observed on Indoor- and Outdoor-Grown Plants

Alexandra Ciorîță,Dorina Podar,Marcel Pârvu,Ioan Gabriel Mircea,Septimiu Cassian Tripon,Cristina Mircea,Lucian Barbu-Tudoran

doi:10.3390/plants10040622

Abstract

Morphological and anatomical traits of the Vinca leaf were examined using microscopy techniques. Outdoor Vinca minor and V. herbacea plants and greenhouse cultivated V. major and V. major var. variegata plants had interspecific variations. All Vinca species leaves are hypostomatic. However, except for V. minor leaf, few stomata were also present on the upper epidermis. V. minor leaf had the highest stomatal index and V. major had the lowest, while the distribution of trichomes on the upper epidermis was species-specific. Differentiated palisade and spongy parenchyma tissues were present in all Vinca species’ leaves. However, V. minor and V. herbacea leaves had a more organized anatomical aspect, compared to V. major and V. major var. variegata leaves. Additionally, as a novelty, the cellular to intercellular space ratio of the Vinca leaf’s mesophyll was revealed herein with the help of computational analysis. Lipid droplets of different sizes and aspects were localized in the spongy parenchyma cells. Ultrastructural characteristics of the cuticle and its epicuticular waxes were described for the first time. Moreover, thick layers of cutin seemed to be characteristic of the outdoor plants only. This could be an adaptation to the unpredictable environmental conditions, but nevertheless, it might influence the chemical composition of plants.

Highlights

The Vinca genus belongs to the Apocynaceae family and comprises three species and one variety: V. major L., V. minor L., V. herbacea Walds. & Kit., and V. major L. var. variegata ‘Louden’ [1]
The epidermises of leaves were studied by scanning electron microscopy (SEM) and details such as the presence or absence, type, shape, and distribution of trichomes and stomata were observed
The stomatal index is related to trichome density, cuticle, spongy and palisade parenchyma thickness, and probably to the lipid and alkaloid content as well

Summary

Introduction

The Vinca genus belongs to the Apocynaceae family and comprises three species and one variety: V. major L. (bigleaf periwinkle), V. minor L. (lesser periwinkle), V. herbacea Walds. & Kit., (herbaceous periwinkle), and V. major L. var. variegata ‘Louden’ (greater periwinkle with white margins) [1]. Vinca plants are intensely studied for their medical properties [3,4,5] due to the rich alkaloid content [6,7,8,9]. These natural products are produced and stored in the aerial parts of Vinca plants [6,10,11], serving as protection against herbivores and pathogens. V. minor is one of the most important medicinal species [14] and the sole source of vincamine in nature, one of the few alkaloids with beneficial effects on cells [3,15]. Quantitative and qualitative differences of the chemical composition in Vinca extracts are dependent on species and the high content of alkaloids, flavonoids, and phenolic compounds, are in correlation with different pharmacological effects [3,16,17,18,19]

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