Marcos Vinicius Meiado

Discontinuous hydration alters seed germination under stress of two populations of cactus that occur in different ecosystems in Northeast Brazil

The water uptake by the seed in arid and semi-arid ecosystems may not be continuous, but may occur in hydration and dehydration cycles (HD). In order to investigate the benefits of discontinuous hydration on seed germination of Pilosocereus catingicola subsp. salvadorensis subjected to environmental stresses, an imbibition curve was determined and times X , Y and Z selected, corresponding to 25, 50 and 75% of the first phase of imbibition, respectively. Seeds of two populations (Caatinga and Restinga) were subjected to 0, 1, 2 and 3 HD cycles, with 48 h of dehydration. Water and saline stress responses were tested at five osmotic potentials (0.0, –0.1, –0.3, –0.6 and –0.9 MPa). Discontinuous hydration provided greater tolerance to water and saline stress in the seeds from the Caatinga region. When the seeds were subjected to water stress, the reduction of the mean germination time (MGT) provided by HD cycles decreased with increasing concentration of the solution. In saline stress, the reduction of MGT was greater in the solutions with the highest concentrations. We conclude that the seeds of the same species collected from populations located in different ecosystems have different germination responses after passage through discontinuous hydration and HD cycles. This provides greater tolerance to environmental stresses but with different responses among populations.

Seed germination of Melocactus sergipensis N.P. Taylor & M.V. Meiado, the newest Brazilian cactus destined for extinction

Recently, a new cactus was discovered in an area of the Caatinga, a tropical dry forest of north‐eastern Brazil. Although this discovery is excellent news, Melocactus sergipensis is critically endangered because it is affected by deforestation of native vegetation and chemicals used in the maize crop, next to the holotype locality. The aim of this study was to evaluate the seed germination and seedling survival of the newest Brazilian cactus. All germination treatments were performed at room temperature and white light or continuous darkness. For the evaluation of establishment, 50 seedlings were examined at 30‐day intervals for 5 months. I did not observe seed germination of M. sergipensis in continuous darkness, which shows that the newly discovered species is positive photoblastic. However, a high germinability was observed under white light (80.0 ± 10.8%), indicating that the seeds of the newly discovered species are able to germinate and the light is needed for seed germination. After 5 months, seedling mortality was less than 5%. These results show that the seedlings of the newly discovered cactus can be produced in a glasshouse, providing support for studies on ex situ conservation of a species that could become extinct in the near future.

A new Melocactus from the Brazilian state of Sergipe

Summary: The dwarf Melocactus sergipensis, sp. nov., is described from a single lowland locality in the NE Brazilian state of Sergipe. It is compared with members of the M. VIOLACEUS species group, from which it may have been isolated on calcareous rocks within a former dense, high caatinga forest. Its longer term survival in the wild is in serious doubt, since the surrounding habitat has been converted for agriculture, and thus it is accorded the IUCN Red List status of Critically Endangered.

In situ or ex situ seed conservation: which is the more effective way to maintain seed longevity of an endangered cactus?

With restricted populations and a small number of individuals, Discocactus bahiensis Britton & Rose (Cactaceae) is an endangered species in Brazil and its capacity for the formation of seed banks in the soil and the maintenance of seed viability remains unknown. Thus, the aim of the present study was to determine the most efficient way to maintain viability during storage of seeds of D. bahiensis . Seeds were stored in paper bags and either kept in a cold chamber (7 ± 2°C) in the dark (ex situ conservation) or buried in the soil to a depth of 5 cm in an area of natural occurrence of the species (in situ conservation). Germinability of the seed banks was evaluated monthly for 20 months. During the first 10 months of storage, germinability of the seeds conserved in situ and ex situ was similar to that of recently collected seeds. After this period, a 70% reduction in germinability was found for the seeds maintained in situ and there was nearly complete loss of viability after 12 months of storage in the field (germinability < 10% in the last 8 months of the experiment), indicating the ability to form persistent soil seed banks. In contrast, the seeds stored in the cold chamber maintained greater than 70% germinability throughout the entire analysis period, demonstrating that ex situ conservation is the most efficient way to maintain the viability of the seeds of this endangered species.

Ex Situ Conservation of Cactaceae in the Brazilian Semiarid: Cactarium Guimarães Duque

ex situ conservation of Cactaceae in the Brazilian semiarid: Cactarium Guimarães Duque Cactaceae is one of the most diverse families in the neotropics and a key component of arid environments (Anderson 2001). In Brazil, Cactaceae are represented by 39 genera and about 260 species, distributed in three subfamilies (Cactoideae, Opuntioideae and Pereskioideae), with specimens in all phytogeographic domains of the country: Amazon, Caatinga, Cerrado, Atlantic Forest, Pampa and Pantanal (BFG 2015). The Eastern Brazil is considered the third largest diversity center for this group (Taylor and Zappi 2004). The cactus family is widely distributed in Caatinga, a Tropical Dry Forest that dominates a large portion of the northeastern areas of Brazil (Brazilian semiarid region) (Zappi et al. 2011). This makes it one of the top four species-rich plant families in the ecosystem (Rodal and Sampaio 2002). According to information from the Species List of Brazilian Flora, 95 species and 25 genera, including globose, epiphytes and columnar cacti, were reported in the Brazilian semiarid (BFG 2015). Cacti are recognized for their particular ecological role. Their broad and shallow root systems influence soil erosion processes, while their flowers and fruits are attractive and an important food source for birds, bats, reptiles and insects. In turn, these animals potentially act as effective pollinators and seed dispersers (Locatelli et al. 1997; Taylor and Zappi 2004; Leal et al. 2007; Rocha et al. 2007; Brito-Kateivas et al. 2012; Gomes et al. 2013; Gomes et al. 2014). Additionally,