Abstract
ABSTRACT Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby (Fabaceae-Caesalpinoideae) is a tree of the Amazon region with pioneer characteristics and large seeds with physical dormancy. Using Accelerated Ageing (AA) methodology, seeds were exposed to Moist Heat (40 °C; >97% Relative Humidity; RH) or Dry Heat (40 °C; 22% RH). Furthermore, it was also investigated dormancy release and the primary site of water entrance into the seeds. Seeds tolerate these conditions for up to six days without any reduction in vigour, however, only Moist Heat could overcome seed dormancy, allowing germination. The lens is the water-gap for primary water entry (where the palisade layer is thinner), as seeds with blocked lens did not imbibe. An unusual multi-layered hypodermis of osteosclereids in the seed coat was observed. Our results suggest that the combination of high temperature with high RH is a key factor involved in overcoming dormancy in the natural habitat of this Amazonian species.
Highlights
Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby (Fabaceae-Caesalpinoideae), is a tropical deciduous tree in the Amazon basin, with rapid growth
Using Accelerated Ageing (AA) methodology, seeds were exposed to Moist Heat (40 °C; >97% Relative Humidity; RH) or Dry Heat (40 °C; 22% RH)
Our results suggest that the combination of high temperature with high RH is a key factor involved in overcoming dormancy in the natural habitat of this Amazonian species
Summary
Schizolobium parahyba var. amazonicum (Huber ex Ducke) Barneby (Fabaceae-Caesalpinoideae), (called paricá in Brazil), is a tropical deciduous tree in the Amazon basin, with rapid growth. The largest trees may reach 40 m in height and 100 cm in Diameter at Breast Height (DBH) (Carvalho, 2007). Due to its pioneer character, this tree is recommended for ecological restoration (Carvalho, 2007; Lopes et al, 2015; Schwartz et al 2017). Amazonicum are flattened, oval, with a hard, water-impermeable seed coat (Shimizu et al, 2011) and are classified as having physical dormancy according to Baskin & Baskin (2014). Amazonicum) are smaller, with individual seeds weighing between 0.7 g and 0.9 g (Cruz & Pereira, 2014), compared to seeds of the Atlantic Forest variety known as guapuruvu (S. parahyba (Vell.) Blake var. Seeds of the Amazonian variety (S. parahyba var. amazonicum) are smaller, with individual seeds weighing between 0.7 g and 0.9 g (Cruz & Pereira, 2014), compared to seeds of the Atlantic Forest variety known as guapuruvu (S. parahyba (Vell.) Blake var. parahyba), weighing about 1.9 g (Freire et al, 2015)
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