Myracrodruon urundeuva, a native species from the Brazilian Caatinga, is widely distributed across its endemic region, where it also plays an essential socioeconomic role. The objective of this study was to evaluate the influence of environmental stress on the germination of M. urundeuva seeds harvested in different years (2010 to 2013). Seeds were germinated at constant temperatures between 10 to 40 °C, osmotic potentials from 0 to -0.8 MPa (in polyethylene glycol 6000 solutions), and from 0 to -0.5 MPa (in NaCl solutions). The experiment was conducted according to a completely randomized design, with three replicates of 50 seeds, in a factorial scheme (harvest year x stress intensity) for each environmental stress. Germination data were then analysed using thermal, hydro and halo time models, and future germination responses projected according to climate change scenarios. The germination thermal thresholds ranged from 7.4 to 53.3 oC. The germination base osmotic threshold (using polyethylene glycol) was -0.6 MPa and the base osmotic threshold in NaCl was -0.43MPa. Seeds from different harvest years showed distinct tolerance to environmental stresses. The thermal, hydro and halo-time models were efficient to describe the germinative response of seeds, and the climate models allowed to identify the germination responses of M. urundeuva in future climate. According to the models for future climate (RCP 8.5), the reduction of rainfall by 2100 will directly affect seed germination and seedling recruitment of M. urundeuva.

Seasonally tropical dry forests are among the most threatened environments by climate change. However, these forests, which are at risk of desertification, are still poorly studied and conserved. Seeds of several species endemic to the Caatinga, a Brazilian dry forest, are also understudied, mainly regarding their ability to cope with a hotter and drier climate predicted for the future. For the first time in seeds of Cenostigma microphyllum (Leguminosae), we aimed to study the presence of physical dormancy, temperature and salt tolerance to ascertain the effects of current and future climate on seed germination. Intact and scarified seeds were investigated by incubating at constant temperatures (15 to 40°C) or in NaCl solutions (−0.2 to −1.0 MPa) at 25 and 30°C. Thermal and osmotic thresholds, as well as thermal time and hydrotime constants, were calculated using linear regressions between the germination conditions and germination rate. To predict germination in the future, a heat sum model based on thermal time and hydrotime was applied to current and future climate scenarios. Seeds of C. microphyllum were permeable to water and did not have physical dormancy. The results indicated that increases in temperature are unlikely to affect germination, despite greater sensitivity to salinity presented at higher temperatures. In a future climate, the reduction in the number of weeks with at least 15 mm rainfall will affect the germination timing for the seeds. Thus, we can conclude that under the most pessimistic climate scenario predicted for the future, the seed germination of C. microphyllum may be restricted, likely leading to low seedling recruitment and establishment.Keywords temperature . salt stress . climate change . thermal time model . hydrotime model

-Angico is a species found in several environments in Brazil, with several applications. It is used in the timber industry and mainly in folk medicine. In order to verify a variation in the biometric characteristics and the quality of seeds from different mother-plants in different harvesting years, the following variables were studied: moisture content, diameter, density, electrical conductivity, fresh and dry matter of seedlings, germination percentage and kinetics, in a completely randomized design with a 2x3 factorial arrangement (lots x size). The obtained results showed that angico seeds from different lots showed different physiological quality, possibly due to the climate variations to which mother-plants were submitted in the different years. Seed size directly interferes with seedling growth under both controlled and greenhouse conditions, and it can be used as a vigor indicator for angico seeds.Index terms: physiological quality, biometrics, Fabaceae, angico.Tamanho e vigor de sementes de Anadenanthera colubrina (Vell.)Brenan colhidas em área de Caatinga RESUMO -O angico é uma espécie encontrada em diversos ambientes no Brasil, e apresenta diversas aplicações, sendo utilizado pela indústria madeireira e principalmente na medicina popular. Buscando-se verificar a variação quanto a caracteres biométricos e qualidade de sementes provenientes de diferentes matrizes em diferentes anos de coleta, desenvolveram-se ensaios após o beneficiamento das sementes, em que foram avaliados: teor de água, diâmetro, densidade, condutividade elétrica, matéria fresca e seca de plântulas, porcentagem e cinética de germinação, em delineamento inteiramente casualizado com esquema fatorial 2x3 (lotes x tamanho). Os resultados obtidos demostraram que sementes de angico de diferentes lotes apresentam qualidade fisiológica distinta, possivelmente pelas variações do clima as quais as árvores matrizes foram submetidas nos diferentes anos de coleta. O tamanho das sementes interfere diretamente no crescimento de plântulas tanto em condições controladas, quanto em casa de vegetação, podendo ser utilizado como indicativo de vigor para sementes de angico.Termos para indexação: qualidade fisiológica, biometria, Fabaceae, angico.

O objetivo nesse trabalho foi avaliar o efeito de diferentes embalagens e ambientes de armazenamento para manutenção da qualidade fisiológica das sementes de Erythrina velutina Willd. (mulungu). As sementes de E. velutina foram coletadas, beneficiadas e acondicionadas em embalagens de papel Kraft ou plástico transparente e armazenadas a temperatura ambiente (30±5 ºC, 56±6% UR) e em câmara fria (10±2 ºC, 74±4% UR), por um período de até 420 dias. As sementes recém colhidas e as armazenadas por 90, 210, 300 e 420 dias foram avaliadas quanto a teor de água, germinação e de vigor de plântulas. Observou-se que o teor de água das sementes de mulungu foi alterado com o tempo de armazenamento e o tipo de embalagem utilizada. A germinação não foi afetada durante o período de armazenamento para todos os ambientes e embalagens, no entanto, não significou com isto o sucesso no vigor das plântulas ou seja, maior crescimento e acúmulo de biomassa seca. Mesmo ocorrendo a diminuição no vigor das plântulas, com o tempo de armazenamento, em temperatura ambiente, sacos de papel e plásticos até 420 dias, proporcionou uma melhor manutenção da qualidade das sementes de mulungu.

Seed production, quality and germination are likely to be affected by a drastic climate change in semi-arid areas predicted for the end of the century. We evaluated Anadenanthera colubrina var. cebil (Griseb.) Altschu (Fabaceae) seeds of different sizes, populations and harvest years for germination and tolerance to environmental stresses aiming to predict impacts of future climate. Seeds were accessed for germination temperature, salinity and osmotic limits and requirements. Germination of large and small seeds harvested in different populations was evaluated in optimum and stressful temperature, salinity and water deficit. A glasshouse pot assay tested weekly irrigation regimes and seedlings emergence and growth. Optimal temperature for seeds germination was 34.8 oC and limits were 5.6 oC and 50.9 oC. Large and small-sized seeds do not differ in germination, however small seeds are more efficient in stressful conditions. Seedlings can emerge and grow under small weekly irrigation for four months. The predicted increase in temperature will not impair germination, however, the time available for seedling establishment will decrease due to lacking rainfall. The increase in the amount of small-sized seeds produced in drought years is a strategy for coping with harsh environments, rather than a decrease in seed quality.