Responses of the photosynthetic apparatus of Dunaliella tertiolecta (Chlorophyceae) to nitrogen and phosphorus limitation

Nitrogen (N) and phosphorus (P) limitation affect the photosynthetic apparatus of Dunaliella tertiolecta in markedly different ways. When grown at 0.25 d−1 (18% of the resource-saturated maximum rate, μmax = 1.39 d−1) in chemostat cultures, N- and P-limited cells were chlorotic relative to nutrient-replete controls. The lutein-to-chlorophyll a ratio increased under both N and P limitation, whereas the neoxanthin-to-chlorophyll a ratio increased only under P limitation. The ratio of accessory photoprotective pigments (α- and β-carotene) to chlorophyll a increased under N-limited conditions. Despite differences in accessory pigment complement, chlorophyll a-specific light absorption coefficients of N- and P-limited cultures did not differ significantly, and were greater than in nutrient-replete conditions. In contrast, the initial slope of the photosynthesis.irradiance (PE) response curve (αChl) declined under nutrient-limiting conditions. There were slight reductions in the maximum quantum efficiency of ph...