Photosynthetic carbon acquisition in Emphasis Typ

Authors: Dinghui Zou Kunshan Gao Weizhou Chen

Publish Date: 2011/01/08

Volume: 107, Issue: 2, Pages: 159-168

PDF Link

Abstract

The photosynthetic oxygen evolution characteristics were examined in both vegetative blade and sexual reproductive receptacle tissues of Sargassum henslowianum Fucales Phaeophyta from the Shenao bay of Nanao Island China to establish the mechanism of photosynthetic acquisition of inorganic carbon Ci in this species In natural seawater pH 81 ca 22 mM Ci irradiancesaturated net photosynthetic rate NPR was greater by 253 in blade than receptacle whereas dark respiratory rate DR was 2fold higher in receptacle than blade NPR at pH 81 was nearly saturated with the 22 mM Ci for both blade and receptacle However the values of the halfsaturation constant for Ci were sharply increased at pH 90 NPR was significantly affected but DR was remained unchanged with the variation of the pH values in seawater The data from the final pH value derived from the pHdrift experiments and the comparison between the measured and theoretically estimated photosynthetic rates suggested that both blade and receptacle were capable of acquiring HCO3 − in seawater The inhibitors experiments showed that a HCO3 − dehydration mechanism mediated by external carbonic anhydrase activity occurred in both the blade and receptacle tissues of S henslowianum The proton buffer TRIS had no inhibitory effect on NPR at normal pH value in natural seawater pH 81 but it significantly depressed NPR at pH 90 This suggested that proton transport occurred at the outside of the plasma membrane facilitated the operation of the carbon acquisition at pH 90 It was proposed that the strategy of photosynthetic carbon acquisition at higher pH would prevent the alga from the damage of overexcitation and photoinhibition in case of sunshine and calm water We concluded that the blade and receptacle tissues of S henslowianum have similar mechanism of acquisition of exogenous Ci from seawater to drive photosynthesis yet they are differentiated more or less with the photosynthetic propertiesThis study was supported by the Chinese 973 Projects No 2009CB421207 the National Natural Science Foundation of China 41076094 and 30970450 the Program for New Century Excellent Talents in University NCET100375 and the Fundamental Research Funds for the Central Universities SCUT 2009ZZ0074

Keywords: