Dried field populations of Nostoc flagelliforme (Cyanophyceae) require exogenous nutrients for their photosynthetic recovery

The effects of nutrients on the photosynthetic recovery of Nostoc flagellif orme during re-hydration were investigated in order to see if their additio n was necessary. Net photosynthesis was negligible in distilled water witho ut nutrient-enrichment. Addition of K+ resulted in significant enhancement of net photosynthesis, whereas other nutrients (Fe3+, Mg2+, Na+, NO3-, PO43 -, Cl-) and trace-metals (A(5)) showed little effect. The recovered net pho tosynthetic activity increased with the increased K+, and reached the maxim um at concentrations above 230 mu M. Desiccation and re-hydration did not a ffect the dependence of photosynthetic recovery on K+. It was concluded tha t dried field populations of N. flagelliforme require exogenous addition of potassium for photosynthetic recovery and that growth may be potassium-lim ited in nature.