Cereus jamacaru is a widespread Cactaceae of northeast Brazil, largely used as cattle food, and as ornamental and medicinal plant. Despite its distinguished importance, until now, there has been little information about the physiological aspects involved on its germination. The objective of this study was to evaluate the effect of light and temperature interaction on the seed germination and seedling establishment of this plant. The evaluated variables were germination percentage at 7 (% G7) and at 14 days after imbibition (% G14), germination average time index (GSI), germination average time (GAT), germination accumulated frequency (GAF), seedling dry mass and height. The highest % G14 and GSI were at 25 ºC in white light, whereas the highest GAT values were in darkness for all evaluated temperatures. On the other hand, % G14, GSI and GAF had the lowest values in darkness. Seeds germinated even in darkness, being however stimulated by the presence of light. The combination of white light and temperature of 25 or 30 °C is the most appropriate condition for seed germination tests.

Although it has been known that the seed's physiological potential affects its response to osmoconditioning and abiotic stresses, researches involving seed aging and priming associated to abiotic stresses are scarce. The aim of this work was to evaluate the role of seed priming on salt tolerance in sorghum seedlings from seeds with two vigor levels (aged or non-aged) and to verify the organic and inorganic solute contributions as osmoregulators in NaCl-stressed seedlings from aged and primed seeds. The combinations of two seed vigor levels (aged or not), two seed types (primed or not) and two salinity levels (exposed to NaCl at 100 mM or not) were evaluated. In low physiological quality seeds (aged seeds), priming provided an attenuation of salinity's negative effects (0 or NaCl at 100 mM) on seedling growth. The accumulation of Na+ and Cl- ions in NaCl-stressed sorghum seedling shoot from primed seeds indicate a plant osmotic adjustment induced by seed priming, which was efficient in reducing the osmotic stress caused by salinity. Proline was the main organic solute that contributed to osmoregulation in NaCl-stressed sorghum seedling shoot and its levels increased due to seed priming. Changes in inorganic and organic solute contents, in both shoot and roots, could have been induced by seed priming and as a function of salt stress tolerance, although the changes in these organs were poorly related to each other.

O objetivo desse trabalho foi avaliar as alterações citoquímicas em sementes envelhecidas e osmocondicionadas de sorgo durante a germinação na ausência ou presença de NaCl a 100 mM. O lote inicial de sementes de sorgo cv. IPA-1011 foi subdividido em dois sublotes de diferentes níveis de vigor, através do envelhecimento acelerado da metade das sementes, sendo a metade de cada sublote também submetida ao condicionamento osmótico em polietileno glicol 6000 a -0,86 MPa por 48 horas. Posteriormente, quatro subamostras de 50 sementes de cada um desses grupos de sementes foram postas sobre duas folhas de papel de filtro, saturadas com água destilada ou NaCl a 100 mM e colocadas em caixas gerbox (11 x 11 x 3,5 cm) tampadas, as quais foram mantidas em câmara de germinação, sob escuro contínuo e temperatura de 25 ºC, durante 72 horas. As análises citoquímicas foram feitas em sementes embebidas por 0; 24; 48 e 72 horas. As células das sementes de sorgo apresentaram formatos irregulares, variando de elíptico ao arredondado, sendo que a coloração com o azul de toluidina também revelou a presença de núcleos, principalmente em sementes osmocondicionadas, indicando que algumas células apresentaram intensa atividade celular. A presença de proteína foi detectada, principalmente em corpos protéicos no citoplasma das células cotiledonares, enquanto o amido foi identificado na forma de grânulos, principalmente no endosperma. Os tratamentos de envelhecimento acelerado e de osmocondicionamento das sementes, associados ao estresse salino, resultaram em pequenas alterações morfológicas e citoquímicas visíveis durante o período experimental.

The aim of this study was to evaluate the rate of water absorption and cytochemical changes in primed and aged seeds of sorghum during germination under absence or presence of 100 mM NaCl. The initial batch of seeds of sorghum cv. IPA-1011, was divided into two batches of different levels of vigor, by the accelerated aging of half seeds, with half of each batch also referred to the priming of polyethylene glycol 6000 at -0.86 MPa for 48 hours. Four replicates of 50 seeds from each batch were placed on two sheets of filter paper, blotting paper saturated with distilled water and placed inside gerboxes (11 x 11 x 3.5 cm) transparent lids, which were kept in a germination chamber under continuous darkness and 25 ºC for 72 hours. The cytochemical analysis characterization was measured in the soaking times of 0; 24; 48 and 72 hours. The sorghum seeds cells showed irregular shapes, ranging from elliptical to rounded, and the staining with the toluidine blue also revealed the presence of nuclei, especially in primed seeds, indicating that some cells showed high cellular activity. The presence of protein was detected mainly in protein bodies on cytoplasm of cotyledon cells, while the starch was identified in the form of granules at endosperm. The accelerated aging treatments and seed priming, associated to salt stress resulted in little morphological and cytochemical visible changes during the experimental period analyzed.