Alterações fisiológicas e bioquímicas em sementes de arroz submetidas ao estresse térmico

Abstract

Alterações fisiológicas e bioquímicas em sementes de arroz submetidas ao estresse térmico 1 Physiological and biochemistry changes in seeds of rice subjected to heat stress para a malato desidrogenase e de 0,25 a 0,57 µmol de NADPH g -1 MF min -1 para a glicose-6-fosfato desidrogenase). Portanto, pode-se concluir que os testes bioquímicos avaliados podem ser utilizados para identificar o início do processo deteriorativo das sementes de arroz e que temperaturas superiores a 25 ºC depreciam a qualidade destas sementes. Palavras-chave:Oryza sativa. Temperatura. Respiração. Malato-desidrogenase. Glicose-6-fosfato-desidrogenase.ABSTRACT -The purpose of this research was to analyze the effect of different temperatures on the respiratory activity, enzymatic and in process related to the physiological quality of rice seeds, and use the relationship between these parameters to characterize the beginning of the deterioration process of seeds. The seeds were exposed during 24 h and conducted tests for germination, first count germination, index the germination speed, length and dry weight of shoot and roots, electrical conductivity, respiratory activity and activity of the enzymes. The experiment was completely randomized with four replicates and the averages compared by Tukey test (p 0.05) with subsequent analysis of regression. Rice seeds showed that the germination and vigor were reduced above 25 ºC temperatures. Respiratory activity increased with increasing temperature, the same occurred with study enzymes activity in at five days after sowing (ranging from 14.55 at 59.86 µmol of NAD + g -1 MF min -1 for at malate dehydrogenase and 0.25 at 0.57 µmol of at NADPH g -1 MF min -1 for glucose-6-phosphate dehydrogenase). Therefore, it can be concluded that the evaluated biochemical tests can be used to identify the beginning of the deteriorating process of rice seeds and that temperatures above 25 ºC can depreciate the quality of these seeds.

Antioxidant activity of corn seeds after thermal stress

“…However, this answer does not mean that these seedlings would growth efficiently with high vigor, considering exposure to adverse environmental conditions. Similar results were reported in a study performed with rice seedlings subjected to different temperature stress (15, 25, 30 and 35°C) for 24h, where the more vigorous seedlings were those subjected to lower temperatures, between 15 and 25°C (MARINI et al, 2012). However, in the same experiment, higher temperatures (>25°C) did not affect early seedling growth, since growth and dry mass of shoots and roots decreased.…”

“…Climatic conditions in different regions of Brazil are quite diverse and responsible for the most conspicuous environmental stresses, and can influence the natural distribution of plant populations, altering the biochemical and physiological processes in seeds, which can significantly decrease the physiological quality of seeds and, consequently the crop productivity (MARINI et al, 2012). Evidences suggest that the sudden and frequent variations in the climate of Brazilian tropical regions can cause the production of reactive oxygen species (ROS) in seedlings, such as the superoxide radical (O 2 -), hydroxyl radical (OH -), hydrogen peroxide (H 2 O 2 ) and singlet oxygen ( 1 O 2 ) (STANISAVLJEVIĆ et al, 2011).…”

“…However, the production and removal of these ROS are highly controlled (APEL & HIRT, 2004), and this balance can be changed if there is uncontrolled increase of some kind of stress. Temperature is one of the most important factors that influence seed viability and seedling growth (MARINI et al, 2012). It determines the capacity and rate of germination (MEI & SONG, 2010).…”

Balanço Hídrico Mensal Para Dois Municípios Do Estado Da Paraíba

“…A variação destes fatores tem influência direta na duração do ciclo das culturas e no desenvolvimento de seus subperíodos e, conhecê-los é um importante passo para o alcance de maiores produtividades (Fenner et al, 2014). Conforme mostram os estudos de Marini et al, (2012) e Heinemann e Stone (2009), as irregularidades na distribuição das chuvas resultam no aumento do risco para o cultivo, pois a distribuição das chuvas durante o ciclo das culturas são limitantes a produção. De forma que há necessidade de planejamento e técnicas que permitam conhecer o regime hídrico e definir estratégias agrícolas.…”

Effect of carbon dioxide on quality of rice seeds

“…Thus, various alternatives aimed at conserving seed quality have been proposed, such as the use of controlled temperature, airtight storage, and modifications that can facilitate the maintenance of seed viability (MARINI et al, 2012;.This study aimed to evaluate the effect of carbon dioxide on preserving the quality of rice seed.…”