Phenology related nutrient content in leaves of Laguncularia racemosa (Combretaceae) in a tropical lagoon of the Gulf of California, Mexico

Background and Aims: The phenological events in mangroves are usually influenced by factors such as water salinity, photoperiod and/or environmental temperature. This has been documented mainly for species of the family Rhizophoraceae and Acanthaceae; however, accessible studies for the family Combretaceae, e.g., Laguncularia racemosa, are limited. Methods: We collected during one year, monthly, three to four leaves of the penultimate and antepenultimate internode of the branches of 10 trees of Laguncularia racemosa. The collection of leaves was made considering eight phenological stages. The nutrients analyzed in the leaves were: total N, PO43-, K+, Ca2+, Mg2+, SO42-, Na+, Fe2+, Cu2+, B (H3BO3), Mn2+ and Zn2+. Additionally, 10 samples of interstitial water (to measure mayor elements) and sediment (to measure pH and quantify the organic matter content) were taken at a depth between 0.3 to 0.6 m. Key results: The nutrients K+, Ca2+, Fe2+, Mg2+ and total N presented maximum values throughout the development of vegetative sprouting until the development of fruits, which means that the greatest importance of these nutrients is in the production of fruits. The Na+ showed its highest concentration (22.8 g kg(-1)) in the beginning phase of flowering and the minimum during the quiescence (8.7 g kg(-1)). In contrast, SO42-, PO43-, Cu2+, B (H3BO3), Zn2+ did not present differences. Finally, Mn2+ presented 109 mg kg(-1) at the end of vegetative sprouting and 34 mg kg(-1) at maturity and falling of fruits. Conclusions: In the absorption of nutrients, phenological stages and local climatic conditions are important.