Abstract
In this paper, we investigated the seasonal physiological performance and morphological adjustment of Argania spinosa growing under contrasting climatic and biogeographic conditions.Two marginal populations were selected in the main distribution area of the species, one at the Northwest and the other one at the South-west. Trees from the North showed a Mediterranean pattern in Photosynthetic performances, exhibiting maximal carbon assimilation during spring and minimum in summer. In contrast, trees from the South showed a different pattern with maximum values recorded in winter and minimum in spring. Photochemical efficiency of PSII results evidenced the absence of damage to PSII in both sites, probably due to an efficient energy dissipation processed by carotenoid pigments. We recorded increased LMA values in the South, which improves drought resistance. Increasing stomatal length and decreasing stomatal density were registered during the drought season in both populations. A. Spinosa is sensitive to changes in the length of drought stress at its Southern limit. The scarcity of rainfall leading to persistent drought has limited the distribution of the species to the banks of dry Wadis and depressions, where it finds some water compensations during summer. In the North, the summer drought severely impacted the species carbon assimilation.
Highlights
relative water content (RWC) was determined according to the method described by Slatyer and Shmueli Figure 1 Average maximum (Tmax) and minimum (Tmin) monthly air temperature, month(1967).14 0.5 g of fresh leaves were weight- ly rainfall and relative humidity % (RH) during 2016/17/18 annual cycles in the two ed (FW), floated in cold distilled water study sites
Significant differences between sites water use, and growth during the drought of spinosa depend on the season and the sta
An increase in proline concentration has effects mainly cause AN reduction.[21]. This ior was observed in the Southern population been registered during winter in both sites. might be due to the decreased pigment con- in April. This trend is in accordance with a This is in accordance with Díaz Barradas et tent, as well as the inhibition of key enzyme previous study on A. spinosa, which has al. (2010) that associated the increase of activities in the Calvin cycle, photosynthet- shown the existence of a drought-dependent proline concentration to the cold temperaic electron transport chain, and RUBISCO stomatal control.[12]
Summary
RWC was determined according to the method described by Slatyer and Shmueli Figure 1 Average maximum (Tmax) and minimum (Tmin) monthly air temperature, month(1967).14 0.5 g of fresh leaves were weight- ly rainfall and relative humidity % (RH) during 2016/17/18 annual cycles in the two ed (FW), floated in cold distilled water study sites. Concerning sub-stomatal CO2 concentration (Ci), in the South it increased in the summer of both cycles and spring and winter 2017.
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