Comparative ecophysiological effects of drought on seedlings of the Mediterranean water-saver Pinus halepensis and water-spenders Quercus coccifera and Quercus ilex

• Published in: Trees (Berlin, West) Vol. 20; no. 6; pp. 689 - 700
• Main Authors: Baquedano, F J, Castillo, F J
• Format: Journal Article
• Language: English
• Published: Heidelberg Springer Nature B.V 01.11.2006
• Subjects: Antioxidants; Carbon dioxide; Chlorophyll; Efficiency; Photochemicals; Pigments; Pinus halepensis; Quercus; Quercus coccifera; Quercus ilex; Seedlings; Trees; Water conservation; water stress; MED
• ISSN: 0931-1890; 1432-2285
• DOI: 10.1007/s00468-006-0084-0

Ecophysiological and structural traits of seedlings of the water-saver Pinus halepensis and the water-spenders Quercus coccifera and Q. ilex were studied in response to water stress under greenhouse conditions. Water deficit reduced stomatal conductance (g ^sub s^) and, as a consequence, both net CO^sub 2^ assimilation (A) and transpiration rate (E) were also reduced. Water stress also emphasized midday down-regulation of the photochemical efficiency (dynamic photoinhibition) reducing quantum yield of noncyclic electron transport (Φ^sub PSII^), photochemical quenching (qP) and photochemical efficiency of the open reaction centres of PSII ((ProQuest: Formulae and/or non-USASCII text omitted; see image)) and involved an increase of thermal dissipation of excess energy. However, water stress not only induced dynamic photoinhibition but also brought a reduction in F ^sub v^/F ^sub m^ (chronic photoinhibition). Despite the water-saving strategy of P. halepensis that limited net CO^sub 2^ assimilation, this species showed a higher photochemical efficiency and lower photoinhibition than Quercus species. This was not the result of a different photochemical quenching but was linked to a higher value of (ProQuest: Formulae and/or non-USASCII text omitted; see image), indicating a less severe photo-inactivation of PSII. Water stress resulted in a loss of pigment content and in an increase of the carotenoids/chlorophyll ratio, antioxidant capacity and the biomass rate allocated to roots as opposed to that assigned to leaves. P. halepensis showed a lower photoinhibition and antioxidant activity than Quercus species due to its lower pigment content and higher proportion of carotenoids allowing P. halepensis to use, in a more effective way, the lesser excess energy absorbed.[PUBLICATION ABSTRACT]