Format: ORAL

Anselmo Nogueira1, Caroline Souza1,Isadora Schulze-Albuquerque2, Pedro J. Bergamo3, Douglas D. Souza1 and Lorena B. Valado-Mendes4

1Universidade Federal do ABC, São Bernardo do Campo, Brazil. 2Universidade Federal de Pernambuco, Recife, Brazil. 3Instituto de Biociências, Universidade Estadual Paulista, Rio Claro, Brazil. 4Universidade Federal de Minas Gerais, Belo Horizonte, Brazil.

Legumes establish mutualistic relationships with nitrogen-fixing bacteria and pollinators critical for plant reproduction and ecosystem services. However, we know little about how nitrogen-fixing bacteria and soil nutrient availability affect the plants attractiveness to pollinators. We conducted a two-factorial greenhouse experiment to investigate the impact of nitrogen-fixing bacteria (rhizobia) and soil types on flower traits in Chamaecrista latistipula (Fabaceae): rhizobia-inoculated (R+) and non-inoculated (R-) plants in organic-rich matter (OM) and sandy soils. We monitored bud and flower production and analyzed leaf, petal, and anther reflectance curves with a spectrophotometer. Using the bee hexagon model, we estimated chromatic contrasts, a crucial visual descriptor for attracting bees up close and from a distance. We partially corroborate our hypotheses, in which only plants R+ and under sandy soils had a high floral display and color contrasts. On the other hand, the absence of nitrogen-fixing bacteria in the root system or plants growing under OM soil severely reduced flower display and color contrasts, decreasing flower attractiveness to bee pollinators. Our findings indicate that rhizobia positively impacts pollination, particularly in nutrient-limited conditions. This study provides insights into the dynamics of plant-pollinator interactions and underscores the significant role of rhizobia bacteria in influencing key floral traits within tropical ecosystems. These results contribute to understanding the mechanisms governing mutualistic relationships and their consequences for plant fitness and ecological dynamics.