Photosynthetic response of P-deficient Gracilaria tenuistipitata under two different phosphate treatments (original) (raw)

Physiologia Plantarum, 1996

Abstract

Phosphorus-deficient Gracilaria tenuistipitata Zhang et Xia was cultured for 15 days at two different inorganic phosphate (P i ) concentrations: 3 μM (low P i treatment) or 30 μM phosphate (high P, treatment). The amount of ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco), phycobiliproteins, Chl a and total soluble proteins were higher in the high P i than in the low P, treatment. The total N content of the low P i plants was lower than in plants grown at high P i concentrations whereas the amount of total C was highest in low P i plants. The increase of Rubisco content in the high P i treatment (3-fold) was parallel to the enhancement of the maximum photosynthetic rate which increased 5-fold. This correspondence was also found in the low P i treatment in which Rubisco content and maximum photosynthesis did not change significantly from the initial values. The photosynthetic efficiency was also higher at high than at low P i . The high P i plants also showed higher dark respiration and growth rates. The data presented here suggest that marine macroalgae submitted to P i deficiency exhibit a decrease in growth caused not only by P i implication on energy transfer in photosynthesis and respiration, but also by the diminution of the amount of photosynthetic pigments and Rubisco.

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