Seasonal variations in P-I responses of Chara hispida L. and Potamogeton pectinatus L. from stream mediterranean ponds
"The relationship between primary production and irradiance was analyzed over an annual cycle in the mubmerged macrophyte, Chara hispida and Potamogeton pectinatus, of two mediterranean stream ponds. The effect of temperature on photosynthesis was also etudied. The population of P. pectinatus reached maximum production values of 19.67 mgO2g-1 AFDW H-1in December at 20°C. In summer and owing to the development of floating filamentous algae, P. pactinatus growth decreased. This can be observed in a decrease in production and chlorophyll content. At the end of autumn a 'self pruning' mechanism in P. pectinatis caused increase of light penetration and new shoots were observed. C. hipida showed maximum production values in May. In summer, in agreement with temperature increase C. hispida fructifies and decays, increasing P. pectinatus growth and cover in the same pond. Photoinhibition was observed in C. hispina in October, in agreement with a low radiation adaptation owing to an unusual decrease in light penetration in the pond, caused by inputs of suspended material from a fire suffered in the watershed at the end of summer. Variations in temperature had no effet on Pm/R ratio in C. hispida was significant. P. pectinatus showed great adaptation capacityto temperature fluctuations and light penetration reduction."
Auteurs du document :
MENENDEZ M., SANCHEZ A.
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Department Ecology, University of Barcelona, Spain