Physiological aspects of germination and storage of Amburana cearensis (Allemão) A.C.Sm (Fabaceae) seeds

Abstract

Amburana cearensis (Allemão) A.C.Sm. is native tree of Brazil adapted at semi-arid habitats. It has ecological, commercial and medicinal importance. A. cearensis is listed in the red list of endangered species. It is threatened by habitat loss and exploitation for use in folk medicine. The bark is used, in the traditional medicine, to cure respiratory diseases while seeds are used to treat lung diseases. This work aims to study the physiological aspects of germination and storage of Amburana cearensis (Allemão) A.C.Sm. seeds. Four storage conditions were used and assessed during 27 months: airtight container in refrigerator; airtight container in laboratory, paper bags in laboratory and liquid nitrogen during 24 months. Germination test was performed at temperatures of 15, 20, 30, 35, 40 and 45 ºC with a photoperiod of 12 hours. Germination in salt solutions was used salt concentration of 100, 200, 300, 400 and 500 mM. A. cearensis seeds kept in refrigerated environment maintain the viability for at least two years. The ideal temperature in seed germination of A. cearensis is 38 ºC. Accessions differed in seed dry mass, in time until 50% imbibition (IMt50), and time until radicle protrusion (RP). The start of water uptake (TWU) was delayed by more than 4 d despite optimal contact between the seed surface and water, and this delay was stronger for smaller seeds and differed between accessions. Longer delay of imbibition was also correlated with higher optimum temperature for germination rate (To), and with longer time until radicle protrusion in water. The TWU, IMt50, and the RP differed between water and salt treatments for the accessions from the semi-arid habitat. These results suggest that it is not advisable to store A. cearensis seeds in laboratory environment without an airtight container and the delayed of the water uptake forms an adaptation to an environment with high temperature, low precipitation, and saline soils, most likely to spread the risk of completing germination at the start of the rainy season.