Seasonal physiological responses of Argania spinosa tree from Mediterranean to semi-arid climate

Abstract

Argania spinosa (the argan tree) is a slowgrowing tree endemic of Morocco, growing on semiarid areas where no other tree species can live. With the aim of predicting temporal changes in A. spinosa woodlands under a probable increase in aridity, we set off to investigate these questions: how do A. spinosa physiological attributes respond to variations in climatic conditions and seasonality, and which is the set of attributes that most affects tree response to environmental conditions? In three study sites, Beni Snassen (North), High-Atlas (Mountain) and Admine Forest in Agadir (Coastal), gas exchange measurements, photochemical efficiency, leaf water potential and different leaf attributes were monitored in February, July and November of 2006. The Mountain site presents the most continental climate. Trees in this site were the most stressed in summer, having the lowest midday leaf water potential values, photochemical efficiency and assimilation rates. We found a Ψ md threshold around -4 MPa, below which stomatal conductance responds linearly to Ψ md . Plants from the North area never reached this threshold during the study period. Although leaf pigments presented a clear seasonal pattern, leaves from Coastal trees exhibit the highest content for each season. The three study sites were separated by two discriminate functions obtained by canonical discriminant analysis. In summer, the Mountain population is separated from the other sites mainly by assimilation rate and F v /F m , while in winter transpiration rates and chlorophyll content are the main discriminant variables. Our study shows that A. spinosa trees adjust their physiological status and leaf attributes to environmental conditions allowing plants to thrive under a dry climate. Under a scenario of global change, the distribution of the argan tree likely shifts to milder areas.

Physiological and biochemical traits of drought tolerance inArgania spinosa

“…spinosa is considered as drought-tolerant species of the Sapotaceae family (Díaz-Barradas et al 2010). The reduction in Ψ pd , g s and leaf RWC (Table 1) was observed, reflecting a net response to drought as in several studies.…”

“…Some endemic species are well adapted to these conditions like the argan tree in Morocco (Msanda et al 2005;Díaz-Barradas et al 2010). The argan tree [(Argania spinosa (L.) Skeels] is endemic to the Southwestern part of Morocco, where it grows in over 800,000 hectares (Msanda et al 2005).…”

Electrolyte ions and glutathione enzymes as stress markers in Argania spinosa subjected to drought stress and recovery

“…In the Mediterranean ecosystem, plants are subjected to severe and permanent drought stress, particularly during summer months (Nogués and Baker, 2000). Some plants as argan tree [Argania spinosa (L.) Skeels], endemic species to Southwestern part of Morocco, have developed a variety of strategies and mechanisms in response to changes in the environment, especially drought stress (Diaz-Barradas et al, 2010Chakhchar et al, 2015a, b or c). Water restriction can lead to morphological, physiological, biochemical and molecular changes.…”

Genetic diversity and population structure of the endangered argan tree (Argania spinosa L. Skeels) in morocco as revealed by SSR markers: Implication for conservation

“…It is the only representative species of the tropical family Sapotaceae in Morocco (Majourhat et al, 2007). This slowgrowing species may be shrubby in appearance or can grow as a tree reaching 7-10m in height (Díaz-Barradas et al, 2010). Abundant throughout the arid and semi-arid regions of south-west of Morocco, the argan forest is key to maintaining the ecological balance and helps safeguard biodiversity due to its hardy characteristics and its powerful role in protection against desertification.…”