Abstract
The ontogenic change in photosynthetic activity of temperate seagrasses was assessed using pulse-amplitude modulated (PAM) fluorometer: Diving-PAM. Seeds of Zostera marina, Zostera asiatica and Zostera japonica were cultured in outdoor tanks. The effect of age on photosynthetic activity was determined by minimum fluorescence (F), maximum fluorescence (Fm'), variable fluorescence (&DeltaF), effective quantum yield (&PhiPSII), electron-transport rate (ETR) and leaf absorptivity (AF). Leaf chlorophyll pigments (a, b, a+b & a:b) were also measured. Fluorescence yields, leaf absorbance and chlorophyll pigments increased with age.In contrast, the effective quantum yield (&PhiPSII) and electron-transport rates (ETR) decreased with age. Highest effective quantum yield and electron-transport rates were observed in younger tissue than in older tissue. Z. japonica had the highest yield and electron-transport rates, hence, found to be productive. The results demonstrate that PAM fluorometry is indeed an effective technique in determining temporal changes in the photosynthetic activity of seagrasses over time.
