Acclimation to light in seedlings of Quercus petraea (Mattuschka) Liebl. and Quercus pyrenaica Willd. planted along a forest-edge gradient uri icon

abstract

  • Photosynthetic acclimation of two co-occurring deciduous oaks (Quercus petraea and Quercus pyrenaica) to a natural light gradient was studied during one growing season. In the spring of 2003, 90 seedlings per species were planted along a transect resulting from a dense Pinus sylvestris stand, an adjacent thinned area and a 10-m-wide firebreak (16.5-60.9% Global Site Factor (GSF)). In two dates of the following summer, we measured leaf gas exchange, carboxylation efficiency (CE), chlorophyll and nitrogen content, light-response curves of chlorophyll a fluorescence parameters, and leaf mass per area (LMA). Summer was mild, as evidenced by leaf predawn water potential (Psi(pd)), which reduced the interactive effect of water stress on the response of seedlings to light. Q. pyrenaica had higher LMA, CE, stomatal conductance (g(s) (max)) and photosynthesis per unit area (A(max)(a)) than Q. petraea at all growth irradiances. A(max)(a), LMA, g(s) (max) and electron transport rate (ETR) all increased with light availability (GSF) in a similar fashion in both species. Light had also a clear effect on the organization of Photosystem II (PS II), as deduced by chlorophyll a fluorescence curves. Chlorophyll concentration (Chl(m)) decreased with increasing light availability in Q. pyrenaica but it did not in Q. petraea. Seedlings of Q. petraea acclimated to higher irradiances showed a greater non-photochemical quenching (NPQ) than those of Q. pyrenaica. This suggests a higher susceptibility to high light in Q. petraea, which would be consistent with a better adaptation to shade, inferred from the lower LMA or the lower rate of photosynthesis.

publication date

  • 2007
  • 2006