Stress responses induced by pre-germination treatments and their identification based on seed germination patterns

Tomato is an important vegetable crop in the world and the fruit is widely known as food and as a protector of health. Seed priming improves its germination potential, better seedling establishment, and vigorous growth. Seed priming in water or chemical solutions is a pre-germination treatment that induces mild or stressful stress during the early phases of germination. The primed seed builds a ‘priming memory’ necessary to configure an "acquired stress response" and upon subsequent stress exposures, they respond more quickly and robustly. The tomato seeds were primed in water (20 h at 20-21 oC) and in 200 mM NaCl and KNO3 solutions (10 days at 28-29 oC) (stressful condition) to induce stress responses which were characterized in terms of their patterns of germination and velocity of germination, expressed as the time (hours) to 50 per cent germination (T50), when primed seeds were set to germinate in water and wastewater (stressful conditions). Four replicates of 25 seeds on sheets of filter paper in Petri dishes were moistened with 4 mL of distilled water or wastewater and set to germinate (28-29 oC). KNO3 induced the fastest and strongest stress response. The T50 of germination in water (15 h) and wastewater (27 h) and the patterns of germination were different from those induced by the NaCl solution. T50 of seeds germinated in water (41 h) and wastewater (39 h) required more time for the seeds primed in the NaCl solution The induced stress responses did not affect the total germination.