Kinetics of Imbibition and Light Quality in Echinocactus Platyacanthus LK & O Germination

Abstract

Given that germination is a crucial stage in the development of plants, it is essential to carry out studies on the factors that affect this phase. The optimal conditions for each species should also be defined, especially those that, by their nature, present such problems in their propagation and conservation that render them vulnerable. Many species of the cacti family belong to this group, so this research aims to contribute to the knowledge of some factors that impact the germination of Echinocactus platyacanthus. The first purpose of this work was to describe the kinetics of scarified seeds imbibition at 25, 30, and 35°C and their impact on the germination response. The evaluation of the effects of red light on the germinative response was established as a second purpose. The results showed that the imbibition process in scarified seeds fits a curve of the Weibull model, with 15.03, 15.62, and 18.84 hours α coefficients, and 0.08, 0.09, and 0.45 β coefficients for temperatures of 25, 30, and 35°C, respectively. In non-scarified seeds, the coefficients were 10.85, 13.11, and 13.06 hours α, and 0.12, 0.10, and 0.08 β for temperatures of 25, 30, and 35°C, respectively. Scarification and temperature favor rapid water uptake. The imbibition behavior is similar under both conditions, unlike the final germination percentage. Temperature influences the imbibition percentage and favors germination since the temperature of 35°C registered over 90%. The seeds irradiated with red light recorded 96% germination at 144 and 168 hours, confirming that light quality influences this response. A possible physical latency and mechanical dormancy are ruled out, demonstrating positive photodormancy. Key words: photodormancy, cactus, red light, scarification, germination