Seed Morpho-Anatomy, Dormancy and Germination Requirements in Three Schizanthus Species (Solanaceae) with Ornamental Potential

Schizanthus carlomunozii, S. hookeri, and S. porrigens are herbaceous species native to Chile and Argentina and have high ornamental potential. Their propagation through seeds is challenging due to low and uneven germination percentages. This study aimed to determine the morpho-anatomical characteristics, dormancy, and germination requirements of the seeds of these three species. The seeds from all three species have a flattened and reniform shape with a foveolate testa. However, the seeds of S. hookeri are distinguished by their larger size, more pronounced C-shape, seed coat with more marked prominences, and symmetrically arranged areoles. Histological analysis and imbibition tests with methylene blue revealed that the seeds have well-developed embryos and permeable seed coats, ruling out physical and morphological dormancy. Germination tests under various conditions showed that the seeds of the three species exhibit physiological dormancy. Imbibition in gibberellic acid (200 ppm) proved to be an effective treatment to promote germination. When evaluated in S. hookeri seeds, cold stratification and after-ripening also improved germination. The optimal temperatures for seed germination were calculated to be 26 °C for S. carlomunozii, 19 °C for S. hookeri, and 23 °C for S. porrigens.