Germination and dormancy in achenes of Acanthospermum hispidum DC, a weed species.
A study was carried out on achenes of A. hispidum collected in São Paulo during Mar. 1991-Feb. 1992. A. hispidum produced a high percentage of viable achenes which were dormant immediately after being collected, except for those collected during September. The achenes responded positively to light, and this was not affected by storage. The germination percentage was highest in the temperature range 20-25°C. Achene photosensitivity depended on their water content and germination percentage increased with achene water content. Germination was equally promoted by red and far-red light, and irradiance did not limit germination. Achene colour was not related to their viability or dormancy.