Maternal environment effects on sunflower achene dormancy level: photoperiod and incident radiation

PIZZORNO LUCIANA; ANITA MANTESE; DIEGO BATLLA; LOPEZ PEREYRA MONICA

Congreso; 11th Conference of the International Society for Seed Science; 2014

The presence of dormancy in sunflower achene at harvest is a usual problem for the seed industry, however little is known about the effect of the maternal environment on this trait. Two type of experiments were performed to study the effect of the maternal environment on achene dormancy level: 1) two contrasting sowing dates (November-spring vs January-summer) in Buenos Aires, Argentina (34º S 58º W) and 2) two experiments varying, radiation level, 80% reduction of incident radiation vs natural radiation level, and photoperiod, natural photoperiod (11.75hs) vs extended photoperiod (14hs), during the grain filling period. At harvest and during post-harvest achenes and seeds (achenes without pericarp) were incubated at 25°C in water and under different concentrations of ABA (experiment 2 only). Additionally structural changes in the pericarp were determined through histological techniques. Achenes from crops sown in summer (grain filling in autumn) presented a higher rate of dormancy loss after harvest than achenes from crops sown in spring (grain filling in summer), while embryos presented only minor differences in germination. Photoperiod did not affect embryo or achene dormancy level. Radiation level also did not affect embryo dormancy; however, achenes from plants exposed to a reduced radiation level during grain filling showed a higher rate of dormancy loss after harvest and a lower sensitivity to ABA than those exposed to natural radiation levels. Additionally, a significant reduction in pericarp thickness was observed in treatments showing a higher dormancy release rate after harvest (summer sowing and reduced radiation). Obtained results showed that the maternal environment significantly affects dormancy level of sunflower achenes, and suggest that this effect could be at least partially explained by differences in radiation level experienced by mother plants. Radiation effects could be explained by changes in sensitivity to ABA and pericarp structure.