Priming and temperature limits for germination of dispersal units of Urochloa brizantha (Stapf) Webster cv. basilisk

Abstract

The objective of this study was to evaluate the effect of priming treatments on the upper and lower thermal limits for germination of Urochloa brizantha cv. basilisk, and testing the hypothesis that pré-imbibition affect thermal parameters of the germination. Pre-imbibed seeds both in distilled water (0 MPa) and PEG 6000 solution (-0.5 MPa) were put to germinate in different temperatures. It is suggested that U. brizantha seeds have low response to priming when they were placed to germinate in medium where water is not limiting. The response of U. brizantha seeds to priming is dependent on the temperature and water potential conditions at which the seeds are pre-imbibed, as well as on the germination temperature. The optimum temperature for germination of U. brizantha shift toward warmer temperatures in primed seeds. Priming effect was more pronounced at temperatures closer to the upper and lower limit for germination, but probably that response cannot be accounted for changes in the thermal time constant (θT (g) ) and ceiling temperature (Tc (g) ). Otherwise, a decrease in the base temperature (Tb) was observed in primed seeds, suggesting that the Tb distribution in U. brizantha seeds is influenced by priming.Keywords: palisade grass, osmoconditioning, osmotic potential, thermal time. Priming e temperaturas limites de germinação de unidades de dispersão deUrochloa brizantha (Stapf) Webster cv. basilisk ResumoO objetivo deste estudo foi avaliar o efeito do tratamento pré-germinativo priming sobre os limites térmicos inferior e superior para a germinação de Urochloa brizantha cv. basilisk, e testar a hipótese de que a pré-embebição afeta os parâmetros térmicos da germinação. Sementes pré-embebidas, tanto em água destilada (0 MPa) quanto em solução de PEG 6000 (-0,5 MPa) foram colocadas para germinar em diferentes temperaturas. Os resultados sugerem que sementes de U. brizantha apresentam baixa resposta ao priming quando colocadas para germinar em meio onde a água não é limitante. A resposta de sementes de U. brizantha para o priming é dependente das condições de temperatura e potenciais hídricos em que as sementes são pré-embebidas, bem como para a temperatura de germinação. A temperatura ótima para germinação de sementes de U. brizantha altera-se para temperaturas mais altas em sementes pré-embebidas. O efeito de priming foi mais pronunciado em temperaturas mais próximas do limite superior e inferior para a germinação, mas, provavelmente essa resposta não foi responsável por mudanças na constante tempo térmico (θT (g) ) e temperatura teto (Tc (g)). Por outro lado, uma diminuição na temperatura base (Tb) foi observada em sementes pré-embebidas, sugerindo que a distribuição Tb em sementes de U. brizantha é influenciada pelo priming.Palavras-chave: grama paliçada, condicionamento osmótico, potencial osmótico, tempo térmico.

Hydropriming changes temperature thresholds for seed germination of tree species from the Caatinga, a Brazilian tropical dry forest

“…Similar results showed that Urochloa sp. (Poaceae) primed seeds had their optimum temperature changed to higher temperatures and that effect of priming was more intense at non-optimum temperatures, widening its germination temperature range (Nakao and Cardoso, 2015). In addition, the authors observed that there is generally a higher increase in T c than decrease in T b which may explain the increase in optimal and ceiling temperatures of the species in this study occurring in the Caatinga ecosystem, naturally characterized by high temperatures.…”

“…Seeking to predict the germinative behavior of some species, researchers have resorted to experiments by using controlled conditions and models based on population parameters, such as degree-days (thermal time), which allows estimating the time required for seed germination in a given thermal regime based on germinative parameters (Cardoso, 2011;Nakao and Cardoso, 2015). Such models allow quantifying the germinative response amid temperature changes in the environment.…”

Efficacy of S-metolachlor + glyphosate for Weed Control in Different Levels of Eucalyptus Straw

“…ha −1 there was no significant difference (Table 2). This occurred because the greater volume of straw reduces average daily soil temperature [37] and exposure to light, which are the main regulators of seed germination [38][39][40][41]. The unavailability of light also causes the emergence of abnormal grass seedlings, with the development of only the aerial or root part, which limits photosynthesis and nutrient absorption, leading to the death of the seedlings [42].…”

Effects of thermal pretreatment on the germination and growth of tomato (Solanum lycopersicum L.) under drought stress

“…Các stress nhẹ hay nhanh trước có thể giúp thực vật đáp ứng mạnh hơn hay kéo dài hơn với stress khác sau đó. Nghiên cứu ở Urochloa brizantha cho thấy việc tiền xử lý hột ở 40 ℃ giúp gia tăng khả năng nẩy mầm và tăng trưởng của cây trong điều kiện hạn [4]. Do đó, trong nghiên cứu này, chúng tôi tập trung tìm hiểu ảnh hưởng của tiền xử lý hột với nhiệt lên các biến đổi hình thái, sinh lý và sinh hóa trong quá trình tăng trưởng của cây cà chua trong điều kiện hạn nhằm gia tăng khả năng chịu hạn của cây cà chua.…”