Flood duration differentially affects seed germination, growth and ecophysiology of the swamp tree Citronella gongonha from the southern Neotropics

Abstract

Citronella gongonha is an abundant tree species in flood-prone areas of southern South America. In swamp forests, young and adult individuals of the species are mainly distributed on hummocks. In this study, we address some aspects of the ecology and physiology of C. gongonha that contribute to the knowledge of its distribution in swamp forests. We evaluated seed germination and growth parameters, as well as chlorophyll, malondialdehyde, hydrogen peroxide, nitrate and carbohydrate levels in young C. gongonha plants during different periods of flooding. Germination did not occur under flooding conditions, and seeds persisted only up to 30 days of flooding, losing germination potential as submersion time increased. However, young plants survived a long period of flooding (until 120 days) by reducing growth, developing morphological adaptations and using carbohydrate pools. These results help to explain the distribution pattern of C. gongonha in swamp forests, predominantly on hummocks where soil flooding is attenuated.