Seasonal variation in colleter exudates in Myrcia splendens (Myrtaceae)

Colleters are secretory structures that play a role in protecting meristems from dehydration. Little attention has been given to the effect of seasonal variation on colleter exudates. Therefore, this study aimed to characterise the main chemical groups found in colleter exudates as well as to correlate the chemical nature of the secretion with seasonal variation. We used Myrcia splendens as a model to understand seasonal variation in colleter exudates. For that, meristems and shoot apices of M. splendens were collected and subjected to standard anatomical techniques. In M. splendens, colleters arise from protodermal cells and are similar to trichomes. Mature colleters are conic and composed of a short stalk and a long secretory head. Histochemical analyses found that colleter exudates differed according to the seasonality. Composition of the secretions was more diverse in the dry season than in the wet season. During the dry season, colleters secreted five different compounds (i.e. total polysaccharides, mucilage-pectins, total proteins, total lipids and phenolic compounds), whereas in the wet season, only three compounds were found (i.e. total proteins, total lipids and phenolic compounds). Our study extends what was known in earlier works, demonstrating changes in colleter exudates due to environmental seasonality.