Received 7 February 1997. Accepted 12 May 1997.
THE ROLE OF NITROGEN NUTRITION IN HIGH-TEMPERATURE TOLERANCE OF THE KELP, LAMINARIA SACCHARINA (CHROMOPHYTA)1
Version of Record online: 28 JUN 2008
Journal of Phycology
Volume 33, Issue 5, pages 800–810, October 1997
How to Cite
Gerard, V. A. (1997), THE ROLE OF NITROGEN NUTRITION IN HIGH-TEMPERATURE TOLERANCE OF THE KELP, LAMINARIA SACCHARINA (CHROMOPHYTA). Journal of Phycology, 33: 800–810. doi: 10.1111/j.0022-3646.1997.00800.x
I thank Tim Driscoll for work on many of the experiments and analyses and Dr. R. Cerrato for statistical advice. Dr. R. Korb provided useful comments on the manuscript. Funding was provided by NSF gran t OCE9216280.
- Issue online: 28 JUN 2008
- Version of Record online: 28 JUN 2008
- chlorophyll fluorescence;
- heat stress;
- Laminaria saccharina;
- photosystem II;
Mechanisms of high-temperature tolerance in the kelp Laminaria saccharina (L.) Lamour. were examined by comparing a heat-tolerant ecotype from Long Island Sound (LIS), New York, and a population from the Atlantic (ATL) coast of Maine. Greater heat tolerance was not attributable to greater thermal stability of the photosynthetic apparatus: LIS and ATL plants exhibited similar short-term effects of high temperature on photosynthetic capacity (Pmax) and quantum yield (estimated as the ratio of variable to maximum chlorophyll fluorescence, Fv/Fm. As LIS plants had consistently higher N and protein content than ATL plants, the interaction between nitrogen nutrition and high-temperature tolerance was examined. When grown under high N supply and optimal temperature (12° C), LIS plants had a higher density of photosystem II reaction centers (RCII), higher activity of two Calvin cycle enzymes (ribulose bisphosphate carboxylase oxygenase [RUBISCO] and NADP-dependent glyceraldehyde-3-phosphate dehydrogenase [G3PDH]), and higher Pmax and Fv/Fm than ATL plants. Individual ATL plants, furthermore, exhibited close correlations of RCII density and enzyme activity with N and/or protein content. Variation in RCII density and enzyme activity, in turn, largely accounted for plant-to-plant differences in Pmax and Fv/Fm. Relationships among these parameters were generally weak or lacking among individual LIS plants grown under optimal conditions, apparently because luxury N consumption resulted in excess reserves of photosynthetic apparatus components. Exposure of N-replete LIS and ATL plants to a superoptimal temperature (22° C) for 4 days caused an increase in the minimum turnover time of the photosynthetic apparatus (tau) and a decrease in Pmax, but had no consistent effect on Fv/Fm RCII density, PSU size (chlorophyll a/RCII), or enzyme activities. When plants were subjected to concurrent N limitation and heat stress, however, LIS and ATL populations exhibited quite different responses. All photosynthetic parameters of N-limited ATL plants declined sharply in response to high temperature, resulting in a negative rate of daily net C fixation. In contrast, LIS plants showed a reduction in PSU size, but maintained other parameters, including daily C fixation, at levels similar to those of N-limited plants at optimal temperature. Overall, the ability of LIS plants to accumulate and maintain high N reserves appears to be critical for heat tolerance and, therefore, for survival during summer periods of simultaneous low N supply and superoptimal temperature. ATL plants, which also experience low summer N supply but not superoptimal temperatures, do not accumulate large reserves of nitrogenous components and are unable to tolerate the combined stress. Because low N supply often co-occurs with high temperatures in temperate marine systems, large-scale declines in algal productivity, such as during El Niño events, are probably due to the interactive effect of N limitation and heat stress.