Effect of Heavy Metals （Cd, Cu） on the Gametophytes of Laminaria japonica Aresch

Effects of various concentrations of two heavy metals, namely Cd and Cu, on gametophytes of Laminariajaponica Aresch were determined by recording morphological changes of gametophytes, determining pH values and the heavy metal content of the culture solution, calculating the germination rate of sporophytes, and observing heavy metal （Cd） distribution using a fluorescence microscope. The results showed that heavy metals damaged the gametophytes, and were even lethal, and that the higher the concentration of heavy metal ions, the greater the injury to gametophytes. Gametophytes could not survive in culture solutions containing more than 100 mg/L Cd and 50 mg/L Cu and were only able to survive in culture solution containing a mixture of Cd and Cu up to a concentration of 10 mg/L, which indicates that gametophytes have a higher tolerance to Cd than Cu and that multiple heavy metal ions in solution markedly aggravate the damage to gametophytes compared with individual heavy metal ions. With increases in the concentration of the heavy metal, the burgeoning rate of sporophytes decreased acutely, and solutions containing multiple heavy metal ions caused even more marked harm to sporophytes than solutions containing a single heavy metal ion, because most sporophytes died in mixed solutions. The pH value of the culture medium dropped immediately at the beginning （the first day） of treatment, increased over the following days, and then decreased again. The pH of culture media containing multiple heavy metal ions showed greater variation than media containing a single heavy metal ion, with the extent of the decrease in pH of culture media containing multiple ions being greatest during the last period of the experiment. With increases in the concentration of heavy metals, the capacity of gametophytes to accumulate these ions increased. The blue fluorescent light emitted by the Cd-and Cd-binding protein complex existing in gametophytes in media containing different concentrations of Cd showed clearly the distribution of the ion in gametophytes and the results obtained were consistent with distribution determined using other methods. All results of the present study showed that gametophytes of L. japonica play a remarkable role as heavy metal decontaminators, especially with regard to Cd.

Phototropism of Thalli and Rhizoids Developed from the Thallus Segments of Bryopsis hypnoides Lamouroux

Newly regenerated thalli were used to study the phototropism of Bryopsis hypnoides Lamouroux under different qualities of light. Positive phototropism in the thalli and negative phototropiam In the rhizoida of B. hypnoides were investigated and analyzed in terms of bending. Both thaiii and rhlzoids developed from thallus segments exhibited typical tip growth, and their photoreceptive sites for phototroplam were also restricted to the apical hemisphere. The bending curvature of rhizoids and thalli were determined with unilateral lights at various wavelengths and different fluence rates after a fixed duration of Illumination. The trends of bending from the rhizoid and thallus were coincident, which showed that the action spectrum had a large range, from ultraviolet radiation （366.5 nm） to green light （524 nm）. Based on the bending curvatures, blue light had the highest efficiency, while the efficiency of longer wavelengths （〉500 nm） was significantly lower. External Ca^2＋ had no effect on the bending curvature of thalli and rhlzolda. Blue light （440 nm） induced thallus branching from rhizoids, while red light （650 nm） had no such effect. Fast-occurring chloroplast accumulation In the outermost cytoplasmic layer of the blue light （440 nm）-Irradiated region In the rhizoid was observed, from which protrusions （new thalli） arose after 4 h of the onset of illumination, and this action was thought to be driven by the dynamics of actin microfilamenta.