Viability, germination and in vitro growth of Caesalpinia spinosa from seeds at different phenological stages

Caesalpinia spinosa is a plant species present in South America, capable of adapting to different climatic and edaphic conditions. It is considered a multipurpose species due to its environmental benefits, contributing to the restoration of degraded soils and containing active compounds intended for various industries. Consequently, this study aimed to evaluate the viability, germination and in vitro growth of C. spinosa from seeds in different phenological stages. The development of this research was carried out in parts. First, for the viability study, seeds were classified as immature, mature and overripe, from which embryos were extracted and placed in a 1% tetrazolium salt aqueous solution for 5 hours. Second, the water content in the seeds was determined using thermogravimetric analysis to classify the seeds. Third, the seeds were disinfected with Tween 20 for 10 minutes, 70% EtOH for 1 minute and 1.5% NaClO for 10 minutes. Then, germination pre-treatment was performed with a cut in the distal region of the cotyledon (CT) and removal of the seed coat (ST) and they were cultivated in a basal MS medium supplemented with Gamborg vitamins. The highest viability was observed in immature seeds (SI) and mature seeds (SM), with values of 97.72% and 73.45% and corresponding water content of 52.23% and 7.60%, respectively. Regarding germination, the SI-ST treatment achieved a germination speed of 48.55% at 4 days, while in the interaction of phenological state and scarification, the SI-ST treatment achieved the highest percentage at 93.16%. In terms of growth, the treatments showed no statistically significant differences, with values between 52.26 mm and 64.79 mm. These results indicate that the phenological state of the seeds and the type of scarification are important for obtaining quality seedlings in vitro in a shorter time, which can be used in future reforestation and ecosystem restoration programmes.