The jacaranda of Bahia (Dalbergia nigra (Vell.) Allemão ex Benth) is an endemic tree of a Brazilian neotropical biodiversity hotspot and is of great ecological and economic interest. Given the threat of extinction due to timber overexploitation and climate change, the present study aimed to analyze the physiological and biochemical quality of D. nigra seeds exposed to heat stress. The seeds were sown in a test tube containing woody plant culture medium, kept in a biochemical oxygen demand chamber at 45°C for 0, 24, 48, 72, and 96 hours, and then maintained in the same chamber at 25°C for 30 days. Physiological analyses of moisture, electrical conductivity, germination speed index, normal and abnormal seedlings, seedling length, root length, hypocotyl length, collar diameter, seedling and root dry mass, and Dickson quality index revealed a drop in germination and vigor with prolonged heat stress, dropping from 95% to 0% between 0 and 96 hours. This was accompanied by a reduction in the content of carbohydrates, lipids, and proteins. Therefore, the vigor and quality of seedlings is negatively influenced by exposure to heat stress at 45°C.
Study Implications: Dalbergia nigra is a species of high economic interest due to its high-quality wood. In the face of climate change, it is necessary to understand the behavior of seeds under temperature above the ideal. The quality and vigor of seedlings produced in vitro at a temperature of 45°C are negatively affected with the increase in hours of heat stress. In addition, the contents of lipids, carbohydrates, and proteins present in the seed reserves show a sharp drop with heat stress. Ultimately, heat stress significantly affects seed biochemistry and subsequent seedling physiology.
