| Abstract | Experiments in tank cultures with Chondrus crispus Stackh. have shown that the dipeptide citrullinyl-arginine can accumulate to high concentrations when plants are supplied with nitrate or ammonia at low temperatures. With nitrate only, low light intensity can limit the rate of accumulation of the dipeptide which, in the natural habitat, can affect plants in midwinter or in shade. In nature, citrullinyl-arginine accumulates throughout the winter months when nitrate is available and growth is restricted by low temperatures. Nitrate levels in the sea fall rapidly in the spring at a time when conditions for growth are improving with increasing irradiance and temperatures. Nitrogen reserves sustain the plants and allow them to take advantage of favorable growth conditions. |
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