We investigated the thermal thresholds to seed germination and the variations in abscisic acid (ABA) levels and oxidative metabolism during seed dormancy-breaking and germination in two palm species with differences in desiccation tolerance. We used Mauritia flexuosa (buriti palm, desiccation-sensitive seeds) from swampy habitats (Veredas) and Attalea speciosa (babassu, desiccation-tolerant seeds) from the transition zone between the forest and semi-arid region (drained soils). Germination was evaluated at 15–40°C after dormancy-breaking (operculum removal). At optimal temperature for both species (30°C), embryos were sampled in distinct germination phases – dry, imbibed, after operculum removal and at early germination – and used for quantifying ABA and hydrogen peroxide (H2O2) content, antioxidant enzyme activities and for histolocalization of superoxide anion (O2−). Seeds of M. flexuosa germinated only in a narrow temperature range (25–35°C), while A. speciosa seeds germinated between 15 and 40°C. After operculum removal, reduced ABA levels in embryos of M. flexuosa were accompanied by constant H2O2 levels, while in A. speciosa, similar levels of ABA and H2O2 were maintained throughout all germination phases. The presence of O2− was restricted to the haustorium, and an increase in O2− accumulation was observed in both species after operculum removal. Similarities were noted between both species regarding enzyme activities; however, the activities were higher in embryos from M. flexuosa. The presence of O2− only in the haustorium indicates that this region of the embryo is an active structure following imbibition and is involved in germination itself, not just functioning in reserve mobilization.

我们研究了种子萌发的热阈值以及种子休眠打破和萌发过程中脱落酸 (ABA) 水平和氧化代谢的变化，这两种棕榈树种具有不同的耐干燥性。我们使用来自沼泽栖息地 ( Veredas ) 和Attalea speciosa的Mauritia flexuosa（buriti 棕榈，对干燥敏感的种子）（babassu，耐干燥种子）来自森林和半干旱地区（排水土壤）之间的过渡带。在打破休眠（去除鳃盖）后，在 15–40°C 下评估发芽情况。在两个物种的最佳温度 (30°C) 下，在不同的发芽阶段——干燥、吸水、去除鳃盖后和发芽早期——对胚胎进行取样，并用于量化 ABA 和过氧化氢 (H 2 O 2 ) 含量、抗氧化酶活性和超氧阴离子 (O 2 - ) 的组织定位。M. flexuosa的种子仅在狭窄的温度范围（25-35°C）内发芽，而A. speciosa种子在 15 至 40°C 之间发芽。去除鳃盖后，M. flexuosa胚胎中 ABA 水平降低，同时 H 2 O 2水平恒定，而在A. speciosa中，ABA 和 H 2 O 2的水平在整个发芽阶段保持不变。O 2 -的存在仅限于吸器，在去除鳃盖后两个物种中都观察到O 2 -积累增加。两个物种在酶活性方面有相似之处；然而，来自M. flexuosa的胚胎的活性更高。O 2的存在-只有在吸器中表明胚胎的这个区域是吸收后的活跃结构并且参与发芽本身，而不仅仅是在储备动员中发挥作用。