Fluorescence and photosynthetic competency in single eggs and embryos of Ascophyllum nodosum (Phaeophyceae)

Pulse amplitude modulation (PAM) fluorometry was used in 2004 and 2005 to measure chlorophyll a fluorescence associated with photosystem II in eggs and embryos of Ascophyllum nodosum (Linnaeus) Le Jolis from the Atlantic coast of Nova Scotia. Fucoid eggs and embryos were maintained in the laboratory for 8 days over which fluorescence measurements were taken. Newly released eggs saturated at about 20 mu mol photons m(-2) s(-1) with maximum electron transport rate (rETR(max)) declining to < 3 after 3 days. Embryos Saturated at about 50 mu mol photons, m(-2) s(-1) and rETR(max) increased to > 11 by day 3. Although some egg senescence was apparent by day 3, some eggs continued to generate a strong photosynthetic signal throughout the 8-day experimental period, even though rETR(max) was reduced. Differences in photosynthetic responses associated with fertilisation were apparent in F-v/F-m, within 24 h. and in rETR(max) after 2 days. Eggs showed relatively stable or declining responses, whereas embryos showed stable or increasing responses. By day 8, quantum yield of embryos was similar to values reported elsewhere for mature fucoids.N