LB 10-124 - The variation in biomass allocation of Sesbania emerus in respond to three different flooding regimes in the Palo Verde National Park, Guanacaste, Costa Rica

Background/Question/Methods:

As sessile organisms, plants have evolved various strategies that would enable them to escape, avoid, tolerate, or mitigate environmental stress by modifying their morphology, physiology, ontogeny, and other life cycle adaptations. These environment-specific modifications result from their genetic diversity and the phenotypic expression of plastic characters. We studied the variation in biomass allocation of Sesbania emerus in respond to three different flooding regimes for two years in the Palo Verde National Park, Guanacaste, Costa Rica. Sesbania emerus is an annual, shrubby, monocarpic plant that grows in non-flooded to heavily flooded sites. We separated plants according to three different levels of flooding: no flooding, intermediate flooding, and maximum flooding based on the depth of the water column during the growing season (0, 30, and 50 cm, respectively). Ten plants were randomly selected within each site and fractionated into primary and secondary roots, stems, branches, main and secondary axis leaves, flowers, and pods. Each part of the plant was brought to constant weight in an oven at 70C.

Results/Conclusions:

Multivariate and univariate analysis, variance revealed significant changes in the total biomass produced by plants growing in the different flooding regimes. deviation and standard errors and calculated relative growth rate (RGR) were performed. In the first year, it was determined that the dry site and the site with maximum flooding had the highest biomass production in most vegetative structures. In the second year, areas of maximum flooding produced the highest biomass. Furthermore, there was significant variation in the patterns of biomass allocation to shoots, roots, and reproduction among the three flooding regimes and among years. Moreover, biomass allocation also changes during the growing season. Reproductive biomass was produced in the first year at the site of maximum flooding, while in the second year it was higher at the site of intermediate flooding. S. emerus shows phenotypic plasticity in its vegetative and reproductive components in response to flooding conditions. In particular, more resources are allocated to above ground organs in plants growing in the maximum flooding areas. In addition, senesce and stop reproduction ends earlier in the non-flooding areas.