Seed dormancy in nightshade

Abstract

Nightshade (Solanum americanum Mill.) is a weed with high percentage of germination and viability under natural conditions. Freshly collected seeds, submitted to a constant temperature of 25°C, show a state of dormancy. This study aims at identifying the factors responsible for breaking this dormancy. Under constant temperatures, the seeds are positively photoblastic and germinate well at temperatures of 15 and 30°C - though not at the intermediate temperatures tested. Storage leads to a loss of dormancy, and alternate temperatures are the main factor in the seeds to display a high percentage of germination in both darkness and light. Freshly collected seeds also suffer the effects of inhibitors in the fruits; analysis shows that these inhibitors do not correspond to phenolic compounds, alkaloids or abscisic acid. As germination of lettuce seed was also inhibited, the compounds present in the nightshade fruits could also be affecting the adaptation of other species.