CRITICAL IRRADIANCE LEVELS AND THE INTERACTIVE EFFECTS OF QUANTUM IRRADIANCE AND DOSE ON GAMETOGENESIS IN THE GIANT KELP,MACROCYSTIS PYRIFERA1 |
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Authors: | Lawrence E Deysher Thomas A Dean |
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Abstract: | Gametophytes of Macrocystis pyrifera (L.) C. Ag. were cultured under a series of quantum irradiances in three photoperiod regimes. The quantum irradiances in each photoperiod were adjusted to provide equal daily irradiation dosages between photoperiods which allowed a critical examination of the interactions between quantum irradiance and quantum dose in determining gametophyte fertility. The lowest quantum irradiance which stimulated gametogenesis in more than 50% of the female gametophytes was 5 μE·m?2·s?1. The saturating irradiance was ca. 10 μE·m?2·s?1 at photoperiods of 12 h or greater. In terms of daily quantum dose, the lowest dose at which greater than 50% gametogenesis occurred was 0.2 E·m?2·d?1. However, this critical quantum dose was higher (0.4 E·m?2·d?1) when instantaneous irradiances were less than 5 μE·m?2·s?1. The saturation quantum dose was also affected by the rate at which the quantum dose was received and varied from 0.4 to 0.8 E·m?2·d?1. Gametophytes in all three photoperiods reached 100% fertility at quantum irradiances above 5 μE·m?2·s?1. Photoperiod effects were small and could be accounted for by quantum dosage effects. |
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Keywords: | gametophytes gametogenesis Macrocystis irradiance quantum dose photoperiod Laminariales |
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