Características funcionais de sementes e estratégias de germinação em uma floresta tropical sazonalmente seca

Abstract

In seasonally dry tropical forests, water is a limiting resource for germination and plant growth. Therefore, dormancy, orthodoxy and storage of reserves represent functional traits that coordinate strategies of resistance to desiccation in seeds, and are crucial for ensuring the survival of species, especially during periods of water restriction. Combining this theoretical knowledge with restoration initiatives is the key to ensuring the successful restoration of these forests. This dissertation intends to understand the dynamics of investment in functional characteristics of seeds and how they affect the germination process in seasonally dry forests of the Caatinga. For this purpose, we used germination tests and quantified seed size, stored reserves and seed coat investment for 22 native tree species. In the first chapter, we aimed to answer how the occurrence of seed dormancy modulates germination strategies, and to propose suitable methodologies for seedling production. We found species that produce non-dormant seeds, physical and physiological dormant seeds, presenting two strategies for colonizing the environment that are influenced by the size of the seeds and the speed of germination. The species produce seeds that use dormancy or orthodoxy as strategies to distribute germination over time and tolerate the dry period in the seed banks. In the second chapter, we tested how the functional traits of seed protection and nutrition affect germination strategies. Trade-offs related to size, stored reserves, tegument and germination speed, coordinate acquisitive and conservative strategies to scape or tolerate the period of low water availability, generating a desynchrony in the recruitment period. In the acquisitive group, small seeds with few reserves invest in more seed coat as a form of protection and germinate fast. In the conservative group, large seeds invest in storing more reserves and germinate slowly. Therefore, this research provides an insight into the different strategies used by plants to produce seeds in the seasonally dry forests of Caatinga, ensuring the survival and colonization of this dry environment. In addition, we have contributed to methodological advances for ecological restoration, maximizing seedling production in the greenhouse.