Nitrogen supply,tissue composition and frond growth rates for Macrocystis pyrifera off the coast of southern California |
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Authors: | P A Wheeler W J North |
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Institution: | (1) W. M. Keck Laboratories, California Institute of Technology, 91125 Pasadena, California, USA;(2) Present address: Museum of Comparative Zoology, Harvard University, 02138 Massachusetts, Cambridge, USA |
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Abstract: | Seasonal changes in ambient NO
3
–
and NH
4
+
, tissue composition (N, C, and C/N ratio), and frond growth rates for Macrocystis pyrifera (L.) Agardh were examined. Ambient NO
3
–
showed distinct seasonal variations. Frond growth rates were variable, but showed no clear correlation to ambient NO
3
–
. The average N content of plant tissue did, however, show the same seasonal variations as ambient NO
3
–
. The longitudinal distribution of total tissue N and various components of tissue N along fronds were also analyzed. Several distinct patterns were found: high levels of protein N at growing tips and elevated levels of soluble N in lower parts of the frond. Free amino acids accounted for a major portion of the soluble N, but neither NO
3
–
nor NH
4
+
accumulated in the plant tissue. The longitudinal distribution of N along the fronds is compared to reported variations in C metabolism, and it is concluded that C and N sourcesink relations do not always coincide and bidirectional translocation may occur. |
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Keywords: | |
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