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Physiological responses of Zostera marina and Cymodocea nodosa to light-limitation stress.

Silva J, Barrote I, Costa MM, Albano S, Santos R - PLoS ONE (2013)

Bottom Line: Their maximum photosynthetic rates were significantly reduced with shading.The different carbohydrate energy storage strategies found between the two species clearly favour C. nodosa's resilience to light deprivation, a condition enhanced by its intrinsic arrangement of the pigment pool.On the other hand, Z. marina revealed a lower tolerance to light reduction, mostly due to a less plastic arrangement of the pigment pool and lower carbohydrate storage.

View Article: PubMed Central - PubMed

Affiliation: CCMAR - Centro de Ciências do Mar, Faro, Portugal.

ABSTRACT
The effects of light-limitation stress were investigated in natural stands of the seagrasses Zostera marina and Cymodocea nodosa in Ria Formosa coastal lagoon, southern Portugal. Three levels of light attenuation were imposed for 3 weeks in two adjacent meadows (2-3 m depth), each dominated by one species. The response of photosynthesis to light was determined with oxygen electrodes. Chlorophylls and carotenoids were determined by high-pressure liquid chromatography (HPLC). Soluble protein, carbohydrates, malondialdehyde and phenol contents were also analysed. Both species showed evident signs of photoacclimation. Their maximum photosynthetic rates were significantly reduced with shading. Ratios between specific light harvesting carotenoids and the epoxidation state of xanthophyll cycle carotenoids revealed significantly higher light harvesting efficiency of C. nodosa, a competitive advantage in a low light environment. The contents of both soluble sugars and starch were considerably lower in Z. marina plants, particularly in the rhizomes, decreasing even further with shading. The different carbohydrate energy storage strategies found between the two species clearly favour C. nodosa's resilience to light deprivation, a condition enhanced by its intrinsic arrangement of the pigment pool. On the other hand, Z. marina revealed a lower tolerance to light reduction, mostly due to a less plastic arrangement of the pigment pool and lower carbohydrate storage. Our findings indicate that Z. marina is close to a light-mediated ecophysiological threshold in Ria Formosa.

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Light response curves of Zostera marina and Cymodocea nodosa.Plants submitted to shading treatments of 24, 40 and 75% of naturally available photosynthetically active radiation (CTRL). The model equation of Smith and Talling [15][16] was adjusted to the observed points.
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pone-0081058-g001: Light response curves of Zostera marina and Cymodocea nodosa.Plants submitted to shading treatments of 24, 40 and 75% of naturally available photosynthetically active radiation (CTRL). The model equation of Smith and Talling [15][16] was adjusted to the observed points.

Mentions: The maximum photosynthetic rates of both Zostera marina and Cymodocea nodosa were significantly reduced with the shading treatment (Fig. 1 and Table 1). In Z. marina plants, reductions in Pm increased with the shading level, with significant differences from control to all the shading levels, with the 75% shading level displaying the lowest Pm. In C. nodosa, all levels showed significant differences in Pm relative to the control but not among them; the plants under 75% shading were the exception, with significantly higher Pm than 24% and 40% shading levels. With the exception of the highest shading level, Z. marina Pm rates were always significantly higher (three-fold or more) than those of C. nodosa. The ascending slope at limiting PPFDs (α) decreased in Z. marina from the control to all the shading levels, while in C. nodosa an opposite trend was observed, with all the shading levels displaying higher α values than control plants (Table 1). The saturation irradiance (Ik) of Z. marina was not affected by shading, whereas in C. nodosa it decreased at least four-fold from the control to all shading levels, with no significant differences among these (Table 1).


Physiological responses of Zostera marina and Cymodocea nodosa to light-limitation stress.

Silva J, Barrote I, Costa MM, Albano S, Santos R - PLoS ONE (2013)

Light response curves of Zostera marina and Cymodocea nodosa.Plants submitted to shading treatments of 24, 40 and 75% of naturally available photosynthetically active radiation (CTRL). The model equation of Smith and Talling [15][16] was adjusted to the observed points.
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3842938&req=5

pone-0081058-g001: Light response curves of Zostera marina and Cymodocea nodosa.Plants submitted to shading treatments of 24, 40 and 75% of naturally available photosynthetically active radiation (CTRL). The model equation of Smith and Talling [15][16] was adjusted to the observed points.
Mentions: The maximum photosynthetic rates of both Zostera marina and Cymodocea nodosa were significantly reduced with the shading treatment (Fig. 1 and Table 1). In Z. marina plants, reductions in Pm increased with the shading level, with significant differences from control to all the shading levels, with the 75% shading level displaying the lowest Pm. In C. nodosa, all levels showed significant differences in Pm relative to the control but not among them; the plants under 75% shading were the exception, with significantly higher Pm than 24% and 40% shading levels. With the exception of the highest shading level, Z. marina Pm rates were always significantly higher (three-fold or more) than those of C. nodosa. The ascending slope at limiting PPFDs (α) decreased in Z. marina from the control to all the shading levels, while in C. nodosa an opposite trend was observed, with all the shading levels displaying higher α values than control plants (Table 1). The saturation irradiance (Ik) of Z. marina was not affected by shading, whereas in C. nodosa it decreased at least four-fold from the control to all shading levels, with no significant differences among these (Table 1).

Bottom Line: Their maximum photosynthetic rates were significantly reduced with shading.The different carbohydrate energy storage strategies found between the two species clearly favour C. nodosa's resilience to light deprivation, a condition enhanced by its intrinsic arrangement of the pigment pool.On the other hand, Z. marina revealed a lower tolerance to light reduction, mostly due to a less plastic arrangement of the pigment pool and lower carbohydrate storage.

View Article: PubMed Central - PubMed

Affiliation: CCMAR - Centro de Ciências do Mar, Faro, Portugal.

ABSTRACT
The effects of light-limitation stress were investigated in natural stands of the seagrasses Zostera marina and Cymodocea nodosa in Ria Formosa coastal lagoon, southern Portugal. Three levels of light attenuation were imposed for 3 weeks in two adjacent meadows (2-3 m depth), each dominated by one species. The response of photosynthesis to light was determined with oxygen electrodes. Chlorophylls and carotenoids were determined by high-pressure liquid chromatography (HPLC). Soluble protein, carbohydrates, malondialdehyde and phenol contents were also analysed. Both species showed evident signs of photoacclimation. Their maximum photosynthetic rates were significantly reduced with shading. Ratios between specific light harvesting carotenoids and the epoxidation state of xanthophyll cycle carotenoids revealed significantly higher light harvesting efficiency of C. nodosa, a competitive advantage in a low light environment. The contents of both soluble sugars and starch were considerably lower in Z. marina plants, particularly in the rhizomes, decreasing even further with shading. The different carbohydrate energy storage strategies found between the two species clearly favour C. nodosa's resilience to light deprivation, a condition enhanced by its intrinsic arrangement of the pigment pool. On the other hand, Z. marina revealed a lower tolerance to light reduction, mostly due to a less plastic arrangement of the pigment pool and lower carbohydrate storage. Our findings indicate that Z. marina is close to a light-mediated ecophysiological threshold in Ria Formosa.

Show MeSH