CHANGES IN THE GERMINATION REQUIREMENTS OF CIRSIUM-VULGARE WITH STORAGE

Cirisium vulgare (Savi) Ten., a monocarpic, biennial weed orginating f rom the Northern Hemisphere, has become a major problem in South Afric a. The seeds of C. vulgare are produced in summer/autumn and germinate in autumn spring. The seeds have a low-temperature requirement for ge rmination four weeks after seed shed. They become deeply dormant with time. Storage conditions affect the degree of dormancy that develops. Initially, seeds germinate optimally at temperatures between 15 and 20 -degrees-C and are not very light-sensitive. With storage they develop a light requirement for germination. Gibberellic acid substitutes for this light requirement. With time, seeds stored at room temperature d evelop a higher temperature (30-degree-C) requirement for germination.