Interactions between algae

Since the advent of radioactive tracer techniques and their first application in lichen physiology by Smith (1961), much information has accumulated on the interaction between alga and fungus. About 35 lichen species with 12 different types of algal partners have been studied to determine the nature of the substances which pass from the autotrophic alga to the fungus. When a lichen is allowed to photosynthesize in the presence of radioactive (or NaH COg solution) the following events occur. 

In the course of the history of the lichen symbiosis and, indeed, in the histories of all symbiotic systems, there must, because of the trial and error nature of evolution, have been numerous examples of incipient symbiosis. Interaction between various algae and fungi at the unicellular and multicellular level is a matter of common observation, particularly with reference to algal covers on tree trunks. But we still cannot identify a single example of early interaction between alga and fungus as a case of incipient lichen symbiosis. 

Deciphering a beneficial chemical interaction between algae and bacteria... 

Allelopathy is defined as biochemical interactions between one plant or microorganism (alga, bacteria, or virus) and another plant through the production of chemical compounds - secondary metabolites (allelochemicals), which influence, direct or indirect, harmful or beneficial, plant growth and development (Rice 1984). Allelochemicals are present in almost all plants and in many tissues, like leaves, stems, flowers, fruits, seeds, roots, or pollen and may be released from plants into the environment by volatilization, leaching, root exudation, and decomposition of plant residues (Chou 1990). 

Bouarab K, Potin P, Correa J, Kloareg B (1999) Sulfated oligosaccharides mediate the interaction between a marine red alga and its green algal pathogenic endophyte. Plant Cell 11 1635-1650 Bryant JP, Chapin FS, Klein DR (1983) Carbon/nutrient balance of boreal plants in relation to vertebrate herbivory. Oikos 40 357-368... 

De Nys, R., Coll, J. C., and Price, I. R., Chemically mediated interactions between the red alga Plocamium hamatum (Rhodophyta) and the octocoral Sinularia cruciata (Alcyonacea), Mar. Biol., 108, 315, 1991. 

An increasing number of specialized interactions between small mobile invertebrates and chemically defended algae or sessile invertebrates have been reported in the marine environment,6167183 and such interactions are also well known between terrestrial plants and insects.200 However, there is some debate as to the ultimate factors driving this ecological specialization. Several authors have suggested that a plant s value as a refuge from predators (i.e., enemy-free space 84201) may be more important than the value of the plant as a food resource,202 but this... 

Examinations of global-scale patterns of secondary metabolite production frequently look at current interactions between existing algae and herbivores and infer past patterns of selective pressures from them.26 6290 91 These studies rarely take into account the evolutionary histories of the algal and herbivore taxa that are common at different sites. Examinations of the evolutionary origins of groups and their dispersal patterns over time may provide valuable insights into the evolution of interactions, patterns of chemical defense concentrations, and selective pressures for the production of chemical defenses. 

Detailed studies on and Fb have been hampered by the property that their EPR spectra are not additive. This property has been attributed to a magnetic interaction between reduced F and Fg, indicating that they are very close to each other. The values of F and Fg are -540 and -590 mV respectively in spinach PS I particles. Their values are always in that range, but their relative values vary in different plant species for example, F has a more negative than Fb in barley and in a halophilic alga. The shape and temperature dependence of the EPR spectra of F and Fb are typical of iron-sulfur proteins. They are considered to be 4Fe-4S centers, since after modification by dimethyl sulfoxide their spectrum is characteristic of 4Fe-4S centres and because their Mossbauer spectra are also in agreement with that attribution. The presence of 10-12 Fe-S pairs in each PS I centre is compatible with this assignment (for reviews, see Refs. 25 and 26). 

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