Climate and microenvironmental parameters affecting anthesis and nectar secretion for Polaskia chende and P. chichipe, endemic columnar cacti from the Tehuacán Valley, Puebla
Keywords:climate change, drought, energy balance, photosynthetic photon flux, temperature.
Anthesis is a process of paramount ecological importance because it allows access of pollinators to floral structures enabling fertilization and an eventual fruit development. Anthesis is regulated by endogenous and exogenous factors, so changes in the environment can have effects on this process. In the present study, the climate of Acatepec, Puebla was obtained for determining possible climate change scenarios. Also, some microenvironmental factors were measured simultaneously with observations of anthesis and nectar secretion for the columnar cacti Polaskia chende and P. chichipe in order to shed some light on our understanding of the environmental control of anthesis for these species. Climate change scenarios estimated an increase in January minimum temperature of 1.12 °C for the year 2020, 2.16 °C for the year 2050, and 3.24 °C for the year 2080. A decrease in annual mean precipitation was also estimated; in particular, reductions of 15.23, 18.34, and 23.62 % were respectively estimated for the same years. Nectar production for P. chende fluctuated throughout the day while for P. chichipe the production was constant. Sugar concentrations were 33.0 ± 1.2 and 27.6 ± 2.2 °Brix, respectively. Both species had diurnal anthesis and their flowering occurred in the winter. In this case, floral evocation can be induced by periods of low temperatures. Therefore, if, at is it expected, winters are increasingly warmer, reproductive development for these species could be reduced owing to an insufficient accumulation of chill units or a decoupling between anthesis and pollinator activity may occur (Cleland et al., 2007). Under a scenario of imminent increase in winter temperatures and a reduction in rainfall, a better understanding of the costly process of reproduction can contribute to an assessment of vulnerability of these species.