Seed and Seedling Susceptibility to Phased Moisture Stress in Soil

Seeds of calabrese and carrot treated with fungicide were sown in soil at three levels of moisture stress causing a range of effects on seed germination or seedling emergence. After periods of up to 3 weeks the soil was either rehydrated directly, or rehydrated after a short period of severe dehydration. Seed and seedling losses appeared to be almost entirely due to seedling death after germination in the conditions of severe dehydration, but even then some germinated seeds survived these conditions. Seed deterioration or death was implicated only in carrot when seeds were dehydrated after being held for from 1 to 3 weeks in soil at —10 × 105 Pa. A model for seed moisture effects on deterioration and survival is proposed.