Enzyme activity in the micropylar region of Melanoxylon brauna Schott seeds during germination under heat stress conditions

Abstract: Recent studies indicate that global temperatures will rise substantially in the 21st century, leading to the extinction of several plant species, as plant metabolism and germination are greatly affected by temperature. Melanoxylon brauna, a tree species native to the Atlantic Forest that occurs from northeastern to southeastern Brazil, is one of the many species threatened by global warming. Despite the economic and ecological importance of M. brauna, studies investigating the influence of heat stress on seed germination and biochemical responses are still incipient. This study aimed to evaluate enzyme activity in the micropylar region of M. brauna seeds during germination under heat stress conditions. Endo-β-mannanase, α-galactosidase, polygalacturonase, pectin methylesterase, pectin lyase, total cellulase, 1,3-β-glucosidase, and 1,4-β-glucosidase activities were determined in micropyles of seeds imbibed for 24, 48 and 72 h at 25, 35 and 45 °C. Seed germination was highest at 25 °C. Endo-β-mannanase activity was not detected under any of the experimental conditions, but imbibition temperature had a significant effect on the activity of all other enzymes.

摘要：近期研究表明，21世纪全球气温将大幅上升，由于植物代谢与萌发过程极易受温度影响，多种植物物种将因此面临灭绝危机。Melanoxylon brauna是一种原产于巴西东北部至东南部大西洋森林的乔木树种，也是受全球变暖威胁的众多物种之一。尽管M. brauna具有重要的经济与生态价值，但针对热胁迫对其种子萌发及生化响应影响的研究仍较为匮乏。本研究旨在探究热胁迫条件下，M. brauna种子萌发过程中其珠孔端区域的酶活性变化。本研究在25℃、35℃及45℃条件下，对吸胀24、48及72小时的M. brauna种子珠孔区域的内切-β-甘露聚糖酶（Endo-β-mannanase）、α-半乳糖苷酶（α-galactosidase）、多聚半乳糖醛酸酶（polygalacturonase）、果胶甲酯酶（pectin methylesterase）、果胶裂解酶（pectin lyase）、总纤维素酶（total cellulase）、1,3-β-葡萄糖苷酶（1,3-β-glucosidase）及1,4-β-葡萄糖苷酶（1,4-β-glucosidase）活性进行了测定。结果显示，M. brauna种子的萌发率在25℃时达到最高；所有实验条件下均未检测到内切-β-甘露聚糖酶活性，但吸胀温度对其余所有酶的活性均存在显著影响。