A STUDY ON COMPARISON OF SEED DORMANCY AND GERMINATION IN THREE SPECIES OF DODDER

In this study three important species of dodder were compared for seed dormancy, optimal light and temperature conditions for germination and superficial structure of seeds. The effect of mechanical and chemical scarification, stratification or chilling and different forms of nitrogen on dormancy breaking was studied. The results showed that there are differences in optimal conditions for germination in three species. The rate of dormancy, the mechanical and chemical factors and stratification did not have similar effect on dormancy breaking in three species. The light had no inhibitory effect on germination, and in Cuscuta monogyna the alternative light caused high germination in seeds. Sulfuric acid, potasium nitrate and mechanical scarification (grinding by stone)caused breaking of seed dormancy in all the species. The results showed the cause of dormancy exists in seed coat and probably it caused dormancy by production of mechanical barrier. The seed coat of dodder was investigated by scanning electron microscopy. The seeds in species were different in dormancy and superficial structure of seed. Dormancy in Cuscuta monogyna was lower than two other species and its surface of seed was smoother than two other species. Dormancy in Cuscuta planiflora was deeper in comparison to two other species. Its surface of seed was rougher than others. The effective factors in dormancy breaking did not have similar affect on three species of dodder