4.4 Resource production
Damage to flowers of S. aversiflora at different stages of floral development did not interfere with the amount of pollen produced, although lower values were found in damaged flowers than in intact flowers. Florivory in the initial developmental stage of the buds could affect anther development and pollen production, leading to the abortion of the complete floral structure due to the lack of resource to allocate in deformed flowers. In the intermediate or pre-anthesis stage of floral development, florivory can affect the amount of resource through the loss of pollen itself due to the partial or total destruction of the anthers. According to Carper et al. (2016), florivory has the potential to strongly affect the male function of the plant. Haas & Lortie (2020) add that partial florivory can reduce pollen deposition because damage to flowers reduces the frequency of pollinator visits.
Studies on the influence of florivory on pollen production are scarce inSenna species. An investigation similar to the one carried out here with S. aversiflora on florivory at different stages of floral development was conducted with Iris gracilipes A. Gray by Oguro & Sakai (2009). The authors focused more on the effects of florivory on female reproduction, which was negatively affected (Oguro & Sakai, 2009). A study on leaf herbivory in a species of Curcubitaceae revealed that simulated herbivory in 50% of the leaves had a strong effect on pollen production per flower, leading to a considerable reduction in the number of pollen grains produced by damaged plants compared to control plants (Avila-Skar et al., 2003).
The characterization of the floral anatomy of S. aversiflora provided novel information, revealing characteristics that are important for the taxonomic classification of the species as well as in the understanding of its antagonistic and mutualistic ecological relationships. The main anatomical traits that possibly explain why S. aversiflora flowers, and especially its petals, are highly susceptible to florivory are the thin cuticle, low density of trichomes on the surface of the petals, absence of papillae on the epidermis, absence of sclerenchyma and crystals in the mesophyll, and high concentrations of nutritive chemical compounds. These characteristics make the flowers more palatable and accessible to florivores. Finally, we conclude that florivory has significant impacts on the reproduction of S. aversiflora, decreasing the amount of pollen and volume of petal tissues. These impacts underscore the importance of the selective pressure of florivory shaping the evolution of plants, promoting defense and regeneration strategies to ensure the continuity of reproduction.
Author contributions
Edinalva Vital, Natan Almeida and Emília Arruda delimited the general idea of the work. All practical steps of the work and the writing of the original draft, including the conceptual, methodological and discursive writing, were carried out by the first author. The co-authors Natan Almeida, Ana Virgínia and Emília Arruda contributed to the supervision and formal analysis of the manuscript.