Abstract
Drought conditions are the major constraint to the early establishment of Quercus suber species. However, drought responses of this species depend on provenances. The objective of this study was to obtain more comprehensive knowledge on the influence of drought conditions on the response of Q. suber L. seedlings originating from Algeria. Soil water status in soil (SWC) and relative water content (RWC) in leaves, morphological parameters for growth evaluation and physiological parameters, and ectomycorrhization were evaluated in two plots of seedlings: watered (W) and none watered (NW). Ten weeks of water starvation induced a reduction in RWC, ectomycorrhization rate and height and diameter growth of none watered seedlings. Under drought conditions, both soluble sugars and proteins were enhanced while polyphenols and %N decreased. The reduction of soil water content was negatively correlated with carbon isotope discrimination. The survival of the seedlings under these drought conditions was due to two strategies: osmotic adjustment through soluble sugars and proteins accumulations in leaves and an increase in carbon discrimination which enhances the water use efficiency (WUE). Key words: Quercus suber, growth, drought, ectomycorrhization, pigments, sugars, starch, plyphenols, δ13C.
Highlights
Summer drought in the Mediterranean region is characterized by 4 months dry period with little or no precipitations, high temperatures and high irradiance, considering the major constraints for vegetation (Aussenac, 2000; Faria et al, 1999)
The reduction of water availability was accompanied by a significant decrease in leaf relative water status (RWC), the relative water content (RWC) values were 85.43 and 70.78% in watered and none watered seedlings, respectively (Figure 1b)
The increase of carbon isotope discrimination with drought induces an increase in water-use efficiency (WUE) (Shahin et al, 2011). These results showed that drought conditions reduced N% leaves contents while previous results have reported that leaf total nitrogen did not show a significant change in water stressed treatments (Kwak et al, 2011)
Summary
Summer drought in the Mediterranean region is characterized by 4 months dry period with little or no precipitations, high temperatures and high irradiance, considering the major constraints for vegetation (Aussenac, 2000; Faria et al, 1999). The cork oak (Quercus suber) is a western Mediterranean species, widely distributed in Mediterranean forest, presenting significant ecological and economic interests. It is an evergreen and sclerophyllous species growing from the sea level up to 700 m in altitude (Quezel and Médail, 2003). This plant is well adapted to summer conditions because it maintains a favorable ratio between water loss and uptake during the dry period. A decrease in shoots and leaves biomass by reducing growth and root drop is noted (Kurze-Besson et al, 2006; Ksontini et al, 1998)
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