Taxonomic significance of achene morphology of selected Rosa taxa (Rosaceae) occurring in Poland

Andrzej M Jagodziński,Dorota Wrońska-Pilarek,Jan Bocianowski,Irmina Maciejewska-Rutkowska

doi:10.5586/asbp.3493

Abstract

Achenes of roses were rarely studied and the studies were focused on anatomical research, mainly on pericarp structure and its development. We investigated the achene morphology by light- and scanning electron microscopy (LM and SEM) of 17 Rosa taxa from three sections (R. gallica from Gallicanae section, R. pendulina and R. rugosa from Rosa section, and R. agrestis, R. canina, R. canina var. corymbifera, R. dumalis, R. dumalis var. caesia, R. inodora, R. jundzillii, R. micrantha, R. rubiginosa, R. sherardii, R. ×subcanina, R. tomentosa, R. villosa, R. zalana from Caninae section). Eight quantitative and eight qualitative features were examined based on 9181 achenes, in total. Average achene size ranged from 4.37 to 5.39 mm in length and from 2.57 to 3.32 mm in width. The lowest morphological variability among the examined taxa was found in R. canina var. corymbifera, and the highest in R. gallica, R. inodora, and R. sherardii. The most diagnostic features of the achenes studied were suture (visible or invisible), presence or absence of hairs, hairs distribution and density, the exocarp sculpture and cuticle pattern type (we have distinguished four exocarp sculpture and three cuticle pattern types), and length. Qualitative achene features have significantly higher diagnostic value than quantitative ones. Taxonomical value of these features is quite high on the species and section level. Our study has shown that the previously mentioned morphological features of achenes can be used as valuable, additional diagnostic features in delimitation of Rosa taxa at the species and section level. Based on the morphological features of achenes, a determination key for all Rosa taxa studied was created.

Highlights

Species of the Rosa L. genus are distributed throughout temperate and subtropical regions of the Northern Hemisphere, in Europe, Asia, Ethiopia, the Middle East, and North America [1]
The aim of the study is a morphological analysis of achenes of 17 Rosa taxa to estimate the usefulness of investigated features in the taxonomy of the genus
Individual achene sizes ranged from 1.90 mm (R. villosa) to 8.43 mm (R. dumalis) in length and from 0.70 mm (R. villosa) to 5.06 mm (R. canina) in width

Summary

Introduction

Species of the Rosa L. genus are distributed throughout temperate and subtropical regions of the Northern Hemisphere, in Europe, Asia, Ethiopia, the Middle East, and North America [1]. In Europe, depending on taxonomic treatment, 47 [9] or 30–60 [5] naturally growing rose species are recognized, with a majority from the Caninae section [5,9,10,11]. The structure of fruits has been the basis for traditional divisions of the family Rosaceae into subfamilies [2,12,13], these do not always correspond to the latest taxonomic descriptions of this family [14,15,16]. Division of the genus Rosa into subgenera has been based mainly on fruit features [3,5,9]. According to Spjut [17] this represents a multiple fruit called a “pometum”. We use, according to Zieliński et al [19], the more practical term “achenes”, instead of “nutlets” as proposed by some authors (e.g., [5,20,21,22])

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