Adjustment of photosynthetic carbon assimilation to higher growth irradiance in three-year-old seedlings of two Tunisian provenances of Cork Oak (Quercus suber L.)

Abstract

Three-year-old seedlings of two Tunisian provenances of cork oak (Quercus suber L.) differing in climatic conditions at their geographical origin were subjected to increasing light intensities. Gaâfour was the provenance from the driest site and Feija from the wettest site. Low-light adapted seedlings from both provenances were exposed to two light treatments: full sunlight (HL) and low light (LL, 15% sunlight) for 40 days. The CO2-response curve of leaf net photosynthesis (An-Ci curve) established under saturated photon flux density was used to compare photosynthetic parameters between leaves subjected to continuous low light (LL leaves) and leaves transferred from low to high light (HL leaves). Transfer from low to high light significantly increased net photosynthesis (An) and dark respiration (Rd) in Gaâfour provenance but not in Feija. After transfer to high irradiance, specific leaf area (SLA) did not change in either provenance. This suggested that the increase in photosynthetic capacity on a leaf area basis in HL leaves of Gaâfour provenance was not due to increased leaf thickness. Only the seedlings from the Gaâfour provenance were able to acclimate to high light by increasing Vcmax and Jmax.

Drought tolerance in cork oak is associated with low leaf stomatal and hydraulic conductances

“…Acorns were collected from two populations originating from contrasting environments in the northwestern provinces of Tunisia (Fig. 1), as described in Rzigui et al (2017). The first site, the National Park of Feija (36° 30′ 00″ N, 8° 20′ 00″ E), is located in the northern extent of the Kroumirie mountains and is characterized by a cold and humid climate.…”

“…In Tunisia, Staudt et al (2008) examined the release of volatile organic compounds during drought in Tunisian cork oak populations from contrasting climatic conditions. More recently, Rzigui et al (2015Rzigui et al ( , 2017 used seedlings from Feija and Gaâfour provenances to show the intra-specific variability of cork oak in response to high light. Several studies examined the intraspecific variability in the Tunisian cork oak forest, mainly concerning the seasonal variability of gas exchange (Nasr et al 2015, Ben Fradj 2016.…”

“…Cork oak (Quercus suber L.) is a sclerophyllous, evergreen Mediterranean tree species adapted to long dry summer conditions with little or no precipitation, maximum temperatures reaching 35-40 °C, and irradiance exceeding 2000 µmol m -2 s -1 at midday. Previous studies show an intraspecific variability between different Tunisian cork oak provenance differing by their ecology in response to summer drought (Ben Fradj 2016), seasonal variations of leaf gas exchange parameters (Nasr et al 2015, Ben Fradj 2016, and light growth (Rzigui et al , 2017.…”

Delineation of seed collection zones based on environmental and genetic characteristics for Quercus suber L. in Sardinia, Italy

“…The hypothesis is supported by Ramírez-Valiente et al (2009), who asserted that, in spite of the low genetic diversity and the weak among-population divergence using molecular markers, cork oak was able to develop local adaptations in response to natural selection. Additionally, in cork oak seedlings exposed to high irradiance and drought under controlled environment, provenances from dry places exhibited higher tolerance to these environmental stressors, despite no relevant change in morphology (Aranda et al 2005, Rzigui et al 2017. Other studies analyzed the variability of candidate genes related to different environmental conditions, suggesting the existence of local adaptations (Modesto et al 2014, Magalhães et al 2015.…”

Sprouts of shoot-clipped oak (Quercus alba and Q. robur) germinants show morphological and photosynthetic acclimation to contrasting light environments

“…Leaf-level photosynthetic capacity for both species was greatest in the high light environment. Several studies have supported the generalization that leaves which develop under high light availability exhibit greater area-based A max , R d , I c , V cmax , and J max than those which develop under low light availability (Gardiner et al 2009;Jensen et al 2012;Rebbeck et al 2012;Rodríguez-Calcerrada et al 2007;Rzigui et al 2017;Zhang et al 2018). However, seedlings of three oaks, one of which is Q. alba, have previously shown limited photosynthetic and growth responses to shading in their first year (Rebbeck et al 2011(Rebbeck et al , 2012.…”