We investigated the presence and orientation of peripheral vascular bundles in leaves of 81 species representing 72 genera of Aizoaceae. Our study included a wide range of morphological shapes of leaves sampled from all four subfamilies of Aizoaceae, with an emphasis on succulent leaves found in Mesembryanthemoideae and Ruschioideae. Our anatomical studies revealed that only three of the four subfamilies in Aizoaceae have peripheral vascular bundles in their leaves, i.e., Sesuvioideae, Mesembryanthemoideae and Ruschioideae. Apart from Sesuvium (Sesuvioideae), all other species with peripheral vascular bundles have an endoscopic orientation, i.e., the phloem is positioned closer to the epidermis, whereas the xylem is pointing towards the interior of the leaf. This contrasts the situation in other Caryophyllales, where, with the exception of Borszczowia (Amaranthaceae), two different types of three‐dimensional venations were observed. The distinct types of three‐dimensional venation may in turn provide clues to the different pathways by which the similar leaves evolved. Endoscopic peripheral vascular bundles in Aizoaceae were only found in species with an expanded leaf base and (sub‐)cylindrical to trigonous leaves. Although flat‐bladed species of Aizoaceae generally have no peripheral vascular bundles, they were present in Delosperma tradescantioides (Ruschioideae: Ruschieae). Persistent, flat leaves are very rare within the hyperdiverse Ruschieae, which typically have (sub‐)cylindrical to trigonous leaves. Thus, the presence of peripheral vascular bundles in leaves of D. tradescantioides indicates that flat‐bladed, persistent leaves constitute a reversal within tribe Ruschieae. The additional presence of lateral bundles in the outer lamina of leaves of D. tradescantioides can be interpreted as a regain of planate venation. Mapping the evolution of peripheral vascular bundles onto a phylogeny of the Aizoaceae suggests that this character evolved repeatedly within subfamilies Mesembryanthemoideae and Ruschioideae.
AbstrAct:The main goal of this study was to evaluate the performance of two palm species under semi-arid conditions during the rainy and dry periods: the semi-arid native Syagrus coronata and a native to tropical America, Acrocomia aculeata. The leaf water potential, gas exchange, leaf soluble sugars, starch, free amino acids, total soluble protein content and morphological traits were measured.The highest leaf water potential and CO 2 assimilation values in both species were achieved during the rainy period. In response to the low soil moisture content during the dry period, gas exchange when compared with values from rainy period. As evergreen plants, both species maintained intact leaf photosynthetic pigment contents during the rainy and dry periods. Other important traits for drought tolerance are larger adaxial surface hypoderm and cuticle found in both species with higher stomatal density on the abaxial leaf surface.When comparing the species, S. coronata exhibited lower sensitivity to low water availability, showing higher CO 2 assimilation and water use efficiency.
-(Anatomy of the vegetative organs of Cactaceae of the caatinga from Pernambuco). Root and cladode transections of five species of Cactaceae from a "caatinga" of Pernambuco (Harrisia adscendens (Gürke) Britton & Rose; Melocactus × horridus Wedermann; M. zenhtneri (Britton & Rose) Luetzelb.; Tacinga inamoena (Schumann) Taylor & Stuppy, and T. palmadora (Britton & Rose) Taylor & Stuppy), were analyzed to verify diagnostic and adaptative features. The sections were stained with safranin and astrablue and mounted in glycerine. The surveys did not show great differences in the roots inner structure among studied species. In the secondary xylem of the roots broad pericyclic rays occur, representing an important adaptative character in xerophytes. The cladodes present the following diagnostic and adaptative features: type of spines; type and position of stomata; hypodermis structure; presence of crystals in epidermis and hypodermis; type and position of mucilaginous structures; general aspects of the vascular system; occurrence of cortical and medular vascular bundles; and presence of storage parenchyma. The results of this work show that the studied species are typical cacti presenting anatomical features, which can be responsible for the success of these plants in adverse environments as the "caatinga".Key words -anatomy, caatinga, Cactaceae, taxonomy , foram analisadas para verificação de caracteres diagnósticos e adaptativos. As secções foram coradas com safranina e azul de astra e montadas em glicerina. As observações feitas mostraram que a estrutura interna das raízes é bastante similar não sendo observados caracteres diagnósticos. No xilema secundário das raízes ocorrem amplos raios pericíclicos representando um importante caracter adaptativo. O cladódio apresenta os seguintes caracteres diagnósticos e adaptativos: tipos de espinho; tipo e posição dos estômatos; estrutura da hipoderme; tipo e posição das estruturas mucilaginosas; aspecto geral do sistema vascular; ocorrência de feixes corticais e medulares; presença de cristais na epiderme e hipoderme e presença de parênquima aqüífero. Os resultados deste trabalho mostram que as espécies estudadas são cactos típicos apresentando caracteres, que podem ser responsáveis pelo sucesso destas plantas em ambientes adversos como a caatinga. RESUMO -(Anatomia dos órgãos vegetativos de Cactaceae da caatinga pernambucana). Secções de raízes e cladódios de cinco espécies de Cactaceae ocorrentes em uma região de caatinga de Pernambuco (Harrisia adscendens(
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