Plant abundance and distribution are regulated by subtle changes in ecological factors, which are becoming more frequent under global climate change. Species with a higher tolerance to such changes, especially during early lifecycle stages, are highly likely to endure climate change. This study compared the germination adaptability of Halopeplis amplexicaulis and H. perfoliata, which differ in life-form and grow in different environments. Optimal conditions, tolerances and the biochemical responses of seeds to osmotic stresses were examined. Seeds of H. perfoliata germinated in a wider range of temperature regimes and were more tolerant to osmotic stresses than H. amplexicaulis seeds. Neither NaCl nor PEG treatment invoked the H2O2 content in germinating seeds of the tested species. Consequently, unaltered, or even decreased activities of H2O2 detoxification enzymes and non-enzymatic antioxidants were observed in germinating seeds in response to the aforementioned stresses. High and comparable levels of recovery from isotonic treatments, alongside a lack of substantial oxidative damage indicated that the osmotic stress, rather than the ionic toxicity, may be responsible for the germination inhibition. Hence, rainy periods, linked to water availability, may act as a key determinant for germination and H. perfoliata could be less affected by global warming owing to better germinability under high temperatures compared with H. amplexicaulis. Such studies involving biochemical analysis coupled with the germination ecology of congeneric species, which differ in life-form and occurrence are scarce, therefore are important in understanding the impacts of global changes on species abundance/distribution.
Keywords: Halopeplis; biochemical responses; climate change; germination ecophysiology; seed stress tolerance.