Differential Physiological Changes in Stomata in Polyploid Agave spp. Could Indicate Flexibility in CO2 Fixation

Members of Agave L. utilize CAM. To date, research on the physiological and morphological adaptations of Agave has analyzed only a few species. With the aim of understanding basic aspects of the physiological responses of polyploid (2n = 2x = 60 to 2n = 6x = 180) Agave accessions in association with CO2 fixation, we carried out genetic and physiological studies of A. tequilana Weber, A. fourcroydes Lem., and A. angustifolia Haw., which are adapted to two ecoregions in the Yucatán of Mexico: the Regional Roger Orellana-CICY Botanical Garden (RO-CICY) in the city of Merida and the Germplasm Bank of the Scientific-Technological Park of Yucatán (GB-PCTY) located in the Sierra Papacal. Differences in genetic variability in Agave spp. were assessed using AFLP markers. Monitoring of stomatal openings during the night showed differences in polyploid species of Agave. The highest expression levels of PEPC and PEPCK genes were observed at the largest suprastomatol cavity areas. All of the evaluated accessions showed a four-fold increase in internal CO2 during the transition from 23:00 h to 3:00 h, indicating a larger diurnal fixation of internal CO2. The results of PCA, including photosynthetic parameters during night–day, indicated differential physiological responses that suggest the occurrence of five groups within the two ecoregions. The physiological data we report here indicate thar polyploid accessions of Agave exhibited differences associated with CO2 exchange, suggesting that these polyploid taxa may be better adapted to climates with high CO2 concentrations and they could be used in atmospheric CO2 sequestration.