Comparing plants of the same species thriving in flooded and non-flooded ecosystems can help to clarify the interplay between natural selection, plant plasticity and stress adaptation. Genipa americana L. (Rubiaceae) and Guazuma ulmifolia Lam. (Malvaceae) are two tree species widely distributed throughout the neotropical region of Brazil and are known to tolerate long periods of flooding. Both species are commonly found in the Central Amazonian floodplain forests of Northern Brazil, but also occur in the seasonally dry upland savannas of Central Brazil. Flood tolerance would probably not play a major role in savanna populations of these species since savannas of Central Brazil are mostly associated with deep well-drained nutrient-poor soils. By comparing the seed and seedling responses to flooding from these two origins, Pires et al. aimed to gain knowledge on phenotypic plasticity and adaptive evolution of traits related to flood tolerance in these two species.

In their study published in AoBP, Pires et al. compared responses of seeds and seedlings of G. americana and G. ulmifolia to substrate waterlogging or total submergence. Three-month-old floodplain and savannah seedlings of both species survived 30 days of waterlogging or submersion despite suffering significant inhibition in biomass. Submersion triggered chlorosis and leaf abscission in both populations of G. ulmifolia while waterlogging did so only in savannah seedlings. During 30 days of re-exposure to non-flooded conditions, G. ulmifolia plants that lost their leaves produced a replacement flush (yet they attained only half the plant dry mass of non-flooded plants). Both submerged and waterlogged G. americana retained their leaves. Consequently, plant dry mass after 30 days recovery was less depressed by these stresses than in G. ulmifolia. Germination was inhibited by flooding in savannah G. americana seeds but promoted in floodplain seeds. Despite some loss of performance in dryland plants, flood tolerance traits were present in wetland and dryland populations of both species. They are part of an overall stress-response potential that permits flexible acclimation to locally flooded conditions.

Researcher highlight

Cristiane Silva Ferreira obtained a BSc in Biological Sciences from the Federal University of Para in 2000. In 2007 she completed a PhD in Botany under the supervision of Professor Maria Teresa Fernandez Piedade at the National Institute for Amazonian Research. Cristiane currently holds a professorship with the University of Brasilia.

Cristiane is a plant ecophysiologist interested in investigating traits and mechanisms related to flood tolerance with a focus on germination and seedling phases. She has worked extensively with species from Amazonian floodplain forests, where plants are subjected to extended periods of flooding and large variations in water level which can fluctuate 10 m or more.