Application of fluorescent transients to indicate nutrient deficiencies in a microalga Nannochloropsis oceanica

Here we studied the effects of nutrient deficiency, focusing on Ca, N, S, Mg, Fe, on photosynthetic performance of Nannochloropsis oceanica to determine the abilities of fluorescence transients to detect nutrient limitation. We conducted a two-level (replete/deplete) fully factorial experiment for each of 5 nutrients and found different responses to nutrient limitation. A potential indicator of N limitation was trapped energy per reaction center (TRO/RC), as the synthesis of photosynthetic reaction center (RC) declined under N deficiency and eventually the ratio of TRO/RC increased. Photosystem II performance measured by performance index (PIABS) was not compromised under Fe, S and Mg deficiency, whereas the impact of Ca and N was critical. Although interactive nutrient interactions on photosynthetic parameters were observed, relationships were established between net reaction closure (MO) and Mg; dissipated energy flux per RC (DIO/RC) and S; and average quantum yield of photochemistry (phi Pav) and Ca.

Automated summary

In this study, we examined the effects of nutrient deficiency on the photosynthetic performance of Nannochloropsis oceanica, with a focus on Ca, N, S, Mg, and Fe. A factorial experiment revealed different responses to nutrient limitation. The ratio of trapped energy per reaction center (TRO/RC) emerged as a potential indicator of N limitation, as the synthesis of photosynthetic reaction center declined under N deficiency leading to an increase in TRO/RC ratio. Fe, S, and Mg deficiencies did not compromise photosystem II performance, while Ca and N had critical impacts. Although nutrient interactions were observed on photosynthetic parameters, relationships were established between net reaction closure (MO) and Mg, dissipated energy flux per reaction center (DIO/RC) and S, and average quantum yield of photochemistry (phi Pav) and Ca.