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The relationship between calcification and photosynthesis in coral was investigated using standard sea water with enhanced calcium concentration. In standard sea water at 23 degrees C with the calcium concentration increased by 2.5 mmol l(-1), incorporation of calcium into the skeleton increased by 30-61 %, depending on the method of data normalisation, and photosynthesis, measured as (14)C incorporation into the tissues, also increased by 87 %. At 29 degrees C, calcium incorporation into the skeleton increased by 54-84 % and (14)C incorporation increased by 32 % when sea water calcium concentration was increased by 5 mmol l(-1). However, photosynthesis measured as net photosynthetic oxygen production did not increase. Similarly there was no change in respiration rate when coral polyps were incubated in high-calcium sea water. It is conjectured that an increase in photorespiration may be responsible for the latter observations. Bisphosphonate has been considered to inhibit calcification but not photosynthesis in corals. We show that bisphosphonate may not inhibit formation of amorphous calcium carbonate and that the inhibition of calcification is possibly illusory. The data are consistent with the trans-calcification model, which suggests that calcification is a source of CO(2) for photosynthesis in corals.

Gossia, a small genus of physiologically novel rainforest trees restricted to the Western Pacific and belonging to a key neotropical Southern Hemisphere family, the Myrtaceae, is characterized by high foliar manganese (Mn) concentrations. This field study provides a quantitative in planta snapshot detailing cellular localization of foliar Mn and other mineral nutrients in sympatric Gossia grayi N. Snow & Guymer and Gossia shepherdii N. Snow & Guymer endemic to far northeastern Australia, and previously not examined. Elements localized in the cells of fresh hydrated leaf tissues were quantified via in vivo cryo-scanning electron microscopy energy dispersive spectroscopy, a non-invasive method that effectively immobilizes cell contents. Leaf anatomical differences were found between species, along with foliar Mn spatial distribution patterns. Localized cellular Mn concentrations exceeding 600 mmol kg-1 were detected in G. shepherdii, whose Mn accumulation across different mesophyll cell types was heterogeneous compared with G. grayi. In both species there was little evidence to support previous findings on other Gossia species of carboxylate association with excess Mn. The analytical X-ray data strongly implicated chloride as a counter-ion to Mn in the two species examined here. The key findings align with the hypothesis that Mn disposal in the mesophyll is a generic trait in Gossia. This research has forged an emerging view of Gossia as being characterized by unusual cellular metal and mineral accumulation patterns that vary at the species level. It contributes to current limited knowledge about generic plant metallophyty, highlighting that assimilating a broader perspective of the phenomenon demands evaluation of individual taxa through field studies. [ABSTRACT FROM AUTHOR]

Premise of the study: Plants that strongly accumulate metals may be practically beneficial, and also serve as novel resources for increasing fundamental understanding of plant biology. Australian Gossia (Myrtaceae) species are delineated by a conspicuous affinity for the heavy metal manganese (Mn), which is a micronutrient crucial to photosynthesis. This genus includes several Mn hyperaccumulators such as G. bidwillii. Unusually, in G. bidwillii foliar Mn is most highly concentrated in photosynthetic cells, an observation thus far restricted to foliar-Mn accumulation in Mn hyperaccumulators. Recent discovery that several of these Gossia species accumulate other metals in addition to Mn will enable investigation as to whether primary sequestration of metals in photosynthetic tissues is restricted to Mn. Methods: Gossia species known to accumulate nickel (Ni) or aluminum (A1) in addition to Mn were sampled in the field. Complementary proton- and electron-probe data were combined to evaluate in vivo microdistribution patterns of excessively accumulated foliar metals. Key results: It was discovered that in addition to Mn and Ni, Gossia fragrantissima accumulated foliar zinc (Zn) and cobalt (Co), with Mn, Ni, and Co most highly localized in mesophyll cells and Zn primarily located in the upper epidermis. In G. hillii, Mn and A1 were highly concentrated in the palisade and epidermis, respectively. Conclusions: This investigation provides evidence that the primary disposal of excess foliar metals in photosynthetic ceils is not exclusive to Mn. It offers rare intrageneric perspective on metal compartmentation, pointing to significant variation among tonoplastal metal transporters associated with detoxification. [ABSTRACT FROM AUTHOR]

The surface concentration dynamics of Ca2+ and O2 in the scleractinian coral Galaxea fascicularis were investigated by means of 2 mm-sized sensors (mini-electrodes). Mini-electrodes were used to measure the light-regulated uptake of Ca2+ for calcification, and the secretion of O2, produced by photosynthesising zooxanthellae, at the surface of the oral ectoderm of Galaxea polyps. The concentration of Ca2+ measured in the boundary layer of seawater adjacent to the polyp surface was variable but always higher than in bulk seawater in the dark and fell to levels closer to the value in bulk seawater on illumination. The fall in concentration, representing an influx of Ca2+ into the ectoderm, increased with increasing photosynthetic photon flux density of illumination. The decrease in Ca2+ concentration on illumination was insensitive to ruthenium red but sensitive to verapamil and acetazolamide. Oxygen secretion at the ectoderm, manifested by an increase in O2 concentration in the boundary layer, increased on illumination but was not sensitive to any of the inhibitors used in the calcium experiments. The results suggest that Ca2+ uptake involves calcium channels and is coupled in someway to the uptake of inorganic carbon for calcification. Uptake is also strongly coupled to photosynthesis. [Copyright &y& Elsevier]