Pigment composition and concentrations within the plant (Ceratophyllum demersum L.) component of the STS-89 C.E.B.A.S. Mini-Module spaceflight experiment

Plant secondary metabolism in altered gravity

Plans by the space program to use plants for food supply and environmental regeneration have led to an examination of how plants grow in microgravity. Because secondary metabolic compounds are so important in determining the nutritional and flavor characteristics of plants-as well as making plants more resistant to biotic and abiotic stresses-their responses to altered gravity are now being studied. These experiments are technically challenging because temperature, humidity, atmospheric composition, light, and water status must be maintained around the plant while simultaneously altering the g-load, either in the free-fall of orbital spacecraft or on a centrifuge rotor. In general, plants have shown increased accumulation of small secondary metabolites in microgravity (<10(-3) g), while these have decreased in hypergravity (>1-g). Gravity-related changes in the plant environment as well as mechanical loading effects account for these responses.

Zinc protects Ceratophyllum demersum L. (free-floating hydrophyte) against reactive oxygen species induced by cadmium

Evidence for Zn protection against Cd-induced reactive oxygen species in the free-floating hydrophyte Ceratophyllum demersum L. is presented in this paper. Metal treatments of 10 micromol/L Cd, 10 Cd micromol/L supplemented with Zn (10, 50, 100 and 200 micromol/L) and Zn-alone treatments of the same concentrations were used. Using 5,5 dimethyl pyrroline-N-oxide as the spin-probe, electron spin resonance spectra indicated a drastic increase in hydroxyl radicals (OH()) in Cd-10 micromol/L treatments, which was closely correlating with the enhanced formation of hydrogen peroxide (H(2)O(2)) and generation of superoxide radical (O(2)(-)) triggered by the oxidation of NADPH. The supplementation of adding Zn (10-200 micromol/L) to the Cd-10 micromol/L treatments significantly decreased the production of free radicals especially by eliminating the precursors of OH() through inhibition of NADPH oxidation. Cd-enhanced ROS production which substantially increased the oxidative products of proteins measured as carbonyls was effectively inhibited by Zn supplementation.

Cadmium-Zinc interactions in a hydroponic system using Ceratophyllum demersum L.: adaptive ecophysiology, biochemistry and molecular toxicology

The interaction between an essential micronutrient, Zn and a toxic non-essential element, Cd has been comprehensively reviewed based on our experiments conducted with Ceratophyllum demersum L. in a hydroponic system. Since Cd and Zn belong to the group IIB transition elements and show similarities in chemistry, geochemistry and environmental properties, it would be one of the elemental pairs of choice to investigate metal-metal interactions. Evidence in support of the protective role of Zn against Cd toxicity in Ceratophyllum demersum L. is presented in this review. Based on our experimental results, we conclude that the antioxidant properties of Zn play an important role in counteracting Cd toxicity.