Combined effect of water potential and temperature on seed germination and seedling development of cacti from a mesic Argentine ecosystem

Abstract

Global climatic change will be associated with an increase of droughts and heat waves, which can affectseed germination and plant population dynamics. Cactus species from mesic ecosystems are likely to bemore affected by these events than species from arid ecosystems. The aim of the study was to assess thecombined effect of water potentials and temperatures on seed germination and seedling traits in six glo-bose cactus species from Córdoba Mountains: Echinopsis candicans, Gymnocalycium bruchii, G. capillense,G. mostii, G. quehlianum and Parodia mammulosa. A factorial experiment was performed in which fourwater potential levels (0, −0.2, −0.4 and −0.6 MPa) were combined with two temperature levels (25 and32◦C). Germination (%) and mean germination time (T50) were recorded and seedling shape (width andlength) was measured. In general, a decrease in water potential and an increase in temperature resulted inlow germination, with different behaviors among species. At 32◦C and low water potentials, germinationwas low or null for almost all species. There was not a clear trend in the response of T50to the treatments.Seedling development was highly and negatively affected by the combination of factors, particularly atlow water potentials. The responses of the analyzed cactus species to low water potential were similarto those of cactus species from more arid ecosystems. Our results suggest that the studied species wouldbe severely affected by changes in temperature and precipitation as predicted under a climate changescenario.