HONG KONG, Nov 6 (Reuters) - Japanese scientists have identified two light receptors in marine algae which appear to be responsible for the proliferation of these plants.

The scientists hope to use the findings, published in the Proceedings of the National Academy of Sciences, to control unwanted algal growth, such as red tides, or to cultivate coveted species of kelp that are used as food.

In their experiment, the scientists removed the receptors genetically from a species of algae, called vaucheria, and found that the plant could no longer grow even though it was exposed to blue light for the next six months.

Blue light is critical for the survival and growth of marine plants as light of other wavelengths cannot penetrate the thick water mass.

"(What) we did was to destroy the receptor molecules and no branch grew at all (even) with the irradiation of blue light," researcher Hironao Kataoka at the Graduate School of Life Sciences at the Tohoku University said in an interview.

"The function of the blue light receptor was destroyed, so the response (growing of new branches) was destroyed."

Next, Kataoka's team will investigate if these two light receptors are present in other species of marine algae, particularly those that give rise to "red tides", or algal blooms so dense that the water becomes discoloured or murky.

"In future, this kind of research will lead to studies into red tides and how to protect against them," Kataoka said, referring to the possibility of shutting down these receptors to stop unwanted algal blooms.

It is unclear what causes red tides; some are seen as natural occurrences, while others are blamed on coastal water pollution. Toxic algal blooms can devastate marine plant and animal life.

They hope to apply the research to cultivating kelp used as food. Kombu, a species of kelp in the Pacific, is an ingredient in Japanese cuisine that is used to flavour soups and stews.

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