A Drier Maternal Environment Increases Water Stress Tolerance of Alpine Seeds and Seedlings

The environmental conditions experienced by a mother plant during seed development can significantly influence the characteristics and performance of its offspring. These maternal environmental effects are crucial for understanding how plant species respond to climate variability and how they may be able to adapt in rapidly changing environments such as alpine ecosystems. While most studies in alpine environments have focused on the effects of warmer maternal temperatures, the consequences of reduced precipitation remain underexplored. We investigated the effects of a drier maternal environment on (i) seed size, (ii) germination and (iii) seedling water stress tolerance in three Australian alpine species (two forbs and one graminoid). We used rainout shelters to impose a 60% reduction in precipitation on maternal plants for 1 year. Then, seeds from plants in rainout and control plots were collected, measured for size and mass, and tested for germination under a gradient of water potential solutions (0 to -1.0 MPa using PEG 6000). Seedlings were grown and subjected to a gradient of watering treatments (100%, 80% and 60% pot capacity) for 14 days under controlled conditions. A drier maternal environment affected seed and seedling traits in all three species, with life-form and species-specific responses. Seed mass and size decreased in the two forbs but increased in the graminoid. In general, seeds collected from rainout shelters had higher germination under severe water stress (-1.0 MPa). Seedlings from drier maternal environments generally exhibited larger total leaf area and lower physiological stress under severe water stress (60% pot capacity). Our findings demonstrate that reduced precipitation during seed development can enhance offspring drought tolerance in alpine species, particularly under severe stress. These maternal effects may contribute to short-term adaptive responses to climate change by increasing offspring performance under water-limited conditions.