True nectar or stigmatic secretion? Structural evidence elucidates an old controversy regarding nectaries in<i>Anthurium</i>

Premise Floral rewards are essential in understanding floral function and evolution of the relationships between flowers pollinators. Whether sugars present stigmatic exudates Anthurium whether it has nectaries have remained controversial because scarcity structural studies. To solve these questions, we investigated anatomy A. andraeanum to elucidate (1) tepals secretory organs, (2) possess a structurally recognizable nectary, (3) tepalar secretion differs from secretion. Methods structure was assessed through light electron microscopy samples immature, pistillate, staminate flowers. The dynamics starch reserve using histochemical tests, sugar content thin-layer chromatography. Results Sugar analysis did not detect sucrose, glucose, or fructose secretions, but confirmed their presence secretions. Stigmatic produced by papillae; were nonvascularized apex tepals. These characterized modified stomata cells with cytoplasm rich organelles, high calcium oxalate crystals. Conclusions Our results showed for first time on true nectar andraeanum. appears be distinct substance, its often-reported seems result sample contamination. Nectar secretions been often mistaken other species deserve revision this genus.