Natalia Delbón

Although the relationship between adult plants and climate is well established, much less is known about whether closely related species from contrasting climatic environments differ in their regeneration responses. We evaluated the effects of water stress, temperature, and their interaction on germination and seedling traits in six species of Gymnocalycium occurring at three sites along a precipitation gradient in Catamarca, Argentina. Seeds were exposed to four water potentials (0, -0.2, -0.4, and -0.6 MPa, using PEG 6000) and two temperatures (25 and 32 °C). Germination percentage, mean germination time, seedling height, width, and shape index were recorded. Water stress strongly affected germination in all species, while temperature further reduced germination at 32 °C. At 25 °C, most species germinated across the water-potential gradient, although responses differed among species. At 32 °C, germination was largely restricted to the control treatment, indicating a strong temperature effect under water stress. Species from the driest site showed the highest tolerance to water deficit, whereas those from the intermediate-precipitation site exhibited the lowest tolerance. Overall, responses did not follow a linear pattern along the precipitation gradient, while species from the same site showed similar responses. These results suggest that local environmental conditions influence germination strategies.

Resource allocation in plants is a fundamental aspect of life history theory. In Cactaceae, the specific trade‐off between sexual reproduction and vegetative growth has still not been studied. The aim of this work was to assess if there is a trade‐off between growth and reproduction, and to analyse whether both growth and allocation to reproduction depend on size of the individual. In this study, we used Gymnocalycium monvillei, a globose cactus endemic to the mountains of central Argentina, as a model species. Specifically, we analysed the relationship of growth (percentage increase in diameter) and size of individuals (diameter) to seed production, seed mass, germination, and mean germination time. To relativize the effect of size on seed production, two variables were calculated: the ratio of seed production to plant size (RSPS), and the ratio of total seed mass to plant size (RSMS). We found that both seed production and total seed mass were significantly related to cactus size. However, growth was not related to seed mass or to seed production, even when they were relativized. Germination and mean germination time were not related to plant size or growth. In the studied species, a slow‐growing globose cactus, we did not find a trade‐off between growth and reproduction.

Key message Through a multidisciplinary study we found that Gymnocalycium bruchii, an endemic cactus from central Argentina, acts as a dioecious species, which is the first record in this genus. Abstract Cactaceae species are typically hermaphroditic; however, about 2% have other different reproductive systems. These non-hermaphroditic species may develop sexual dimorphism in flowers or other reproductive, vegetative or ecological traits, besides a specific breeding system and floral ontogeny. Therefore, multidisciplinary research is necessary to fully understand reproduction in those species. For this purpose, we studied Gymnocalicium bruchii, a globose cactus endemic to central Argentina that is presumably dioecious or gynodioecious. We made observations in two natural and two cultivated populations. We made morphological observations of plants and flowers, and performed quantitative analyses to determine the sex ratio, size of plants and flowers, flower production, fruiting, among other variables. We performed hand-pollination, self-fertilization and free-pollination tests to determine the breeding system. Finally, we studied the anatomy and ontogeny of the reproductive organs using permanent histological slides of flower morphs at different stages. Our results confirm that Gymnocalicium bruchii is a dioecious species. Female flowers have atrophied anthers and a functional gynoecium that produces fruits and seeds. Male flowers are bigger and have a functional androecium but a sterile gynoecium. In the cultivated population, the sex ratio was 1/1, whereas the number of male individuals was higher in both natural populations. Pollination tests corroborated dioecy. Ontogenetic studies revealed that in female flowers the anthers collapse before microspore maturation, while in male flowers the gynoecium shows normal development of the ovary, style, stigma, and ovules; however, the latter are never fertilized.

As a group, cacti are regarded as plants that tolerate water scarcity, since they present a number of adaptations. However, little is known about how species of the family varied their morphoanatomical characteristics along environmental gradients. The aim of this study was to analyze how six Gymnocalycium species occurring in three sites along a precipitation gradient (arid site: G. pugionacanthum, G. marianae; semiarid site: G. hybopleurum, G. stellatum; subhumid site: G. oenanthenum, G. baldianum) differ in their biomass partitioning and morphoanatomical characteristics. We collected mature individuals of each species and analyzed their biomass partitioning (to spines, aboveground stem, underground stem, main root, and lateral and thin roots), morphological characteristics (such as size ratios, spine length and width, and areole density) and anatomical characteristics (stoma number, and cuticle, epidermis, and hypodermis width). Species differed, both qualitatively and quantitatively, in most of the analyzed variables. For example, biomass allocated to spines was highest in G. pugionacanthum, lowest in G. baldianum, and intermediate in the remaining species. However, these variations were not clearly associated with aridity, but were related to the subgenus of the species. These patterns were clearly observed in the PCA. Phylogenetic relatedness is the main factor associated with morphoanatomical characteristics.

Human action has led to an increase in aridification, making water a progressively scarcer resource. In angiosperms, different species resolve this challenge in diverse ways, mainly through modifications of the xylem network, which is responsible for water efficiency and safety. Xerophytes generally show similar characteristics, but exceptions are rather frequent. One possible explanation for this lack of similarity among cohabiting species is that trade-offs and/or functional coordination between their organs occur and shape alternative survival strategies. Studying species that inhabit a common area can help to identify key traits that determine those diverse strategies and to predict which species might tolerate further environmental change. We here examined the morpho-anatomical wood and bark traits of a group of species that live in a seasonally dry environment in Argentina. In a previous study, we described the leaf traits of these species and we thus aim to complement our findings and outline their strategies to manage water deficits. Our results show that there are different degrees of xeromorphism within this group. Clear xeromorphic traits, such as high vessel frequency and small diameter, were found in most species. However, some presented traits that were appropriate for mesic environments. An overview of leaf and wood traits indicates that the absence of a typical xeric characteristic in the wood might be compensated by the presence of a xeric leaf trait, and vice versa. Collectively, these trait combinations allow these species to survive in dry conditions and could influence their tolerance to increasing aridity.

Background and aims: Sierras de Famatina are an important area of ​​endemism, where two representatives of Trichocereus coexist, whose taxonomic identity is discussed. Trichocereus. pseudocandicans is endemic, with colorful, diurnal flowers; while, T. candicans has a wider distribution, with white and nocturnal flowers. Taking these differences into account, we carried out a morpho-anatomical study of perigonium, gynoecium and fruit, making qualitative and quantitative comparisons. The objective is to generate new information for the genus, provide reliable taxonomic traits, and make inferences about its reproductive biology. M&M: We made temporary and permanent histological preparations of flowers and fruits, using classical techniques. In addition, we analyzed 43 morpho-anatomical variables, which were statistically compared. Results: The entities present similar morpho-anatomical traits but are differentiated by the color of the perigonium and the total size of the flowers. The following characters stand out: the style presents a stilar canal and transmitter tissue, the receptacle and the ovary wall are notoriously different but intimately fused, even after fertilization, circinate ovules, among others. Only 27.9% of the variables analyzed resulted in statistically significant differences, the flowers of T. candicans being slightly larger than those of T. pseudocandicans. Conclusions: The similarity found between the taxa reaffirms their high degree of kinship, and it is possible that T. pseudocandicans is a subspecies or hybrid of T. candicans. On the other hand, the different floral traits could be due to a high phenotypic variability, influenced by the particular characteristics of the Famatina Sierras. Introducción y objetivos: Las Sierras de Famatina son un área importante de endemismo, allí conviven dos representantes de Trichocereus, de los que se discute su identidad taxonómica. Trichocereus pseudocandicans es endémica, con flores coloridas y diurnas; mientras que, T. candicans presenta distribución más amplia, con flores blancas y nocturnas. Teniendo en cuenta estas diferencias, llevamos a cabo un estudio morfo-anatómico del perigonio, gineceo y fruto, realizando comparaciones cualitativas y cuantitativas. El objetivo es generar información novedosa para el género, aportar caracteres taxonómicos confiables y realizar inferencias sobre su biología reproductiva. M&M: Se realizaron preparados histológicos temporarios y permanentes de flores y frutos, utilizando técnicas clásicas. Se analizaron y compararon estadísticamente 43 variables morfo-anatómicas. Resultados: Las entidades presentan características morfo-anatómicas similares, pero se diferencian por el color del perigonio y el tamaño de las flores. Se destacan los siguientes caracteres: el estilo presenta canal estilar y tejido transmisor, el receptáculo y la pared del ovario son notoriamente diferentes pero íntimamente fusionados, incluso luego de la fecundación, óvulos circinótropos, entre otros. Solo el 27,9% de las variables analizadas resultaron con diferencias estadísticamente significativas, siendo las flores de T. candicans levemente mayores que las de T. pseudocandicans. Conclusiones: La similitud encontrada entre los taxones reafirma su alto grado de parentesco, siendo posible que T. pseudocandicans sea una subespecie o híbrido de T. candicans. Por otro lado, los rasgos florales diferentes podrían deberse a una alta variabilidad fenotípica, influenciada por las características particulares que presentan las Sierras de Famatina.

Our objective was to study reproductive biology, seed germination and regeneration, through morphoanatomical and field observations and controlled experiments, to assess reproductive strategies in six rare Flourensia endemic to Central Argentina (F. campestris, F. hirta, F. leptopoda, F. niederleinii, F. oolepis, F. tortuosa). Structure of capitula, flowers, and achenes was described. Capitula were visited by a variety of insects. Achenes required 30–45 days to mature. Fruit set varied significantly among species. Flourensia campestris and F. oolepis were self-incompatible. Seed viability decreased after 19 months and was lost after 32 months. Flourensia oolepis and F. campestris had the highest germination percentages (>60%); the addition of gibberellic acid in 2-months old seeds did not influence germination. The remaining species had lower germination percentages ( 6...