Abstract
Sunflower ( Helianthus annuus L. cv. Toledo-2) seeds were exposed to u.v.-C radiation for 0, 5, 10, 15, 30 and 60 min. Experiments were carried out using dry and hydrated seeds. In each group, two treatments were considered: (1) dry (treatment D0) and hydrated (treatment W0) seeds were germinated immediately after u.v.-C irradiation, and (2) dry (treatment D7) and hydrated (treatment W7) seeds were exposed to irradiation and then stored in darkness 7 days before the initiation of germination. The percentage of normal seedlings was reduced when u.v.-C irradiation exposure durations increased from 5 to 60 min. The percentage of abnormal seedlings increased and showed a maximum for the 60 min exposure time. As compared to treatments D0 and W0, seeds stored 7 days after irradiation (treatments D7 and W7) showed less inhibition. The results suggest that inhibition caused by u.v.-C radiation may be partially reversed during dark storage of seeds; the extent of this recovery varies with seed treatment. When the results from the seed treatments were combined (D0 + D7 and W0 + W7), the ability of seeds to germinate was described by a linear probit regression between germination performance and u.v.-C exposure time. A probit analysis of the percentage of normal seeds indicated that hydrated seeds (W0 + W7) had a sensitivity to u.v.-C irradiation 2.74 greater than that of dry seeds (D0 + D7).
Published Version
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