Field study of leaf photosynthetic performance by a Mediterranean deciduous oak tree (Quercus pubescens) during a severe summer drought
Year: 1995
Type: article
Abstract: SUMMARY Quercus pubescensWilld. is a winter deciduous oak species which co‐occurs in the Mediterranean area with an evergreen oak,Q. ilex.As the knowledge ofQ. pubescensassimilation patterns is poorly documented, we monitored leaf physiological parameters throughout a growing season. In summer, drought was particularly severe, and some trees experienced pre‐dawn water potentials (Ψpd) as low as – 4·5 MPa. Diurnal courses of net photosynthesis, stomatal conductance and I photochemical efficiency of photosystem II (PS II) were recorded on four trees in the field. Maximum assimilation rates (10–16·5 μmol m−2s−1, depending on sampled trees) occurred in spring. Leaf carbon gain recovered in autumn even after water potential fell to – 3·4 MPa. During progressive drought, Ψpddecreased substantially, leaf gas exchange was reduced and showed an important diurnal depression. At – 2 MPa (Ψpd), net photosynthesis and stomatal conductance were still about 5 μmol m−2s−1and 50 mmol m−2s−1, respectively. Pre‐dawn maximal PS II photochemical efficiency was stable to – 4 MPa. The diurnal decrease in photochemical efficiency of PS II (Fv/Fm), measured after 30 min of dark adaptation, was enhanced during drought but maximal values always recovered at sunset, i.e. leaves only experienced short‐term reversible PS II inhibition induced by high light and temperature. In conclusion,Q. pubescensdisplays a strategy of tolerance to drought and an efficient protection against high irradiance.
Source: New Phytologist
Authors: C. DAMESIN And, S. RAMBAL
Institution: Centre d'Écologie Fonctionnelle et Évolutive
Language: English
Subfield: Global and Planetary Change
Field: Environmental Science
Domain: Physical Sciences
Open Access status: green
OpenAlex ID: W2071643718