Secretory duct distribution and leaf venation patterns of Aldama species (Asteraceae) and their application in taxonomy

Abstract

Features of leaf morphology such as secretory duct distribution and venation patterns are important taxonomical tools; however, some species can have variation in these traits. This study evaluates whether the secretory duct distribution in the midrib and venation is similar across different leaves of 17 Aldama species. Six fully expanded leaves (three each of the largest and smallest size) from five distinct plants were selected to analyze the duct distribution. The samples were histologically examined, and the quantitative data were statistically analyzed. The venation pattern was analyzed in five fully expanded leaves of different plants. In all, 23 secretory duct distribution patterns were identified; they showed intra- and inter-species variations except in Aldama anchusifolia (DC.) E.E.Schill. & Panero and A. trichophylla (Dusén) Magenta. The largest number of ducts was not correlated with leaf and midrib dimensions (width and length). Further, Aldama venation could be divided into two groups: (1) pinnate camptodromous brochidodromous type (four species), and (2) acrodromous venation type and its basal and suprabasal variations (13 species). Thus, distinct secretory duct arrangements of the midrib might assist in the discrimination of Aldama species. The venation patterns were also important for distinguishing the majority of species selected.

Can climate and soil conditions change the morpho-anatomy among individuals from different localities? A case study in Aldama grandiflora (Asteraceae)

“…This correlation was not observed by Filartiga et al (2016), who reported such a tendency only in the leaves of Aldama corumbensis, among the 17 species analyzed. However, the position of secretory ducts has been associated with the presence of vascular bundles (Gregio and Moscheta, 2006;Bombo et al, 2012) and, in the case of A. grandiflora, the midrib can present 3 to 5 collateral vascular bundles , which certainly influences the midrib width and the number of secretory ducts in the ground parenchyma.…”

“…The patterns varied within the same population and even within the same individual, depending on the section analyzed. Furthermore, two of the patterns found in A. grandiflora from populations 5 and 6 were not described before in any other Aldama species, even by Filartiga et al (2016), who conducted a detailed study about secretory ducts in Brazilian Aldama species.…”

“…Secretory duct arrangements: The duct arrangements found in the ground parenchyma of the midrib were based on Filartiga et al (2016) who described 23 different types of duct distributions. Different duct arrangements were found in A. grandiflora (Table 4), and the distribution in the different populations is shown in Table 5.…”

“…However, some studies (Kakrani et al, 1991;Sheue et al, 2003;Filartiga et al, 2016) showed that the number and position of secretory ducts can vary, rendering it difficult to use this character as the only parameter of differentiation among species. As previously reported for other Brazilian Aldama species (Filartiga et al, 2016), in A. grandiflora, variation The morphometrical parameters evaluated in this study were not correlated to the altitude of the sites from where the populations were collected, likely because the difference between the amplitude of altitude among the sites was less pronounced than that of sites investigated by in the number and position of secretory ducts was found in the midrib ground parenchyma, and also was observed among individuals from different populations, individuals of the same population, and within the same individual.…”

“…In relation to the duct distribution, Filartiga et al (2016) identified 23 different patterns, based on the number and position of ducts in the ground parenchyma of the midrib. Of the 23 already reported distributions in Aldama species , 12 types, as well as two new patterns, were identified in A. grandiflora in this study.…”