Abiotic factors controlling germination of the multipurpose invasive Prosopis pallida: towards afforestation of salt-affected lands in the subtropical arid Arabian desert.
Prosopis pallida is an exotic invasive tree recently recorded in the hot arid subtropical deserts of the UAE and has the potential for afforestation of degraded arid lands. Little information is available about the effects of abiotic stresses on the germination of this species. Here, we aimed to assess the response of drought (as simulated by polyethylene glycol, PEG) and salinity (NaCl) stresses to light and temperature of seed incubation. Seeds treated with four salinities (0-600 mM NaCl) and seven PEG (0 to - 1.8 MPa) levels were incubated at three temperatures and two light regimes. The results showed that the response of seed germination to NaCl depended on temperature, but on both light and temperatures in PEG. In both NaCl and PEG solutions, germination did not differ significantly between the three temperatures at higher osmotic potentials. Still, it was reduced significantly in the lower potentials when seeds incubated at higher temperatures. Additionally, germination in light and dark did not differ at higher osmotic potentials of PEG, but germination in the dark was significantly higher at lower osmotic potentials. A considerable proportion of seeds that failed to germinate in PEG recovered their germination when transferred to distilled water (62%), but few seeds were able to recover from NaCl (4.2%). The higher tolerance to NaCl indicates that seeds might use sodium and chloride ions as osmoregulators to alleviate the osmotic inhibitory effects. Future research should monitor seedling establishment and growth to explain plant persistence in salt-affected lands in arid environments.