Stomatal morphometry of Andean species and their relationship with spatial variation

Stomata play a fundamental role in maintaining plant homeostasis by regulating the balance between water loss and CO2 absorption required for photosynthesis. Analysis of stomatal traits across environmental gradients provides insight into how plant species are uniquely adapted to their environment and their potential response to environmental change. In the Andes, there is limited information on how stomatal traits vary spatially and with climatic conditions. This study aimed to characterize the morphometry of Andean woody species and corroborate the relationship of stomata characteristics with leaf traits in response to environmental variation. We measured the following traits on each species: stomatal size (SS), stomatal width (SW), stomatal density (SD), stomatal relative area (SRA), leaf thickness (LT), leaf area (LA), and specific leaf area (SLA). These traits were then analyzed to determine their relationships with mean annual temperature (MAT), mean annual precipitation (MAP), mean solar radiation (MSR), latitude, and longitude at the sampling sites. Our analyses showed that stomatal traits largely vary among species. Some species (e.g., Morella pubescens) exhibit high plasticity, suggesting greater resilience to unfavorable climatic conditions. However, the relationships with MAP, MSR, and MAT varied, suggesting that these species employ different mechanisms to avoid water stress and optimize water use. Moreover, we observed relationships between stomatal traits, particularly SS and SW, with latitude and longitude. Similarly, we identified significant correlations between leaf and stomatal traits. Our results suggest that the functional traits of stomata in the individual evaluated from these species respond to their geographic origin and, therefore, to the climatic conditions of their habitat.