Resumo

MARTINON-MARTINEZ, R. Julián; VARGAS-HERNANDEZ, J. Jesús; GOMEZ-GUERRERO, Armando  e  LOPEZ-UPTON, Javier. Carbon isotopic composition in foliage of Pinus pinceana Gordon seedlings subjected to water and temperature stress. Agrociencia [online]. 2011, vol.45, n.2, pp.245-258. ISSN 2521-9766.

Pinus pinceana Gordon grows in semiarid conditions in the northeast and central east of México. Probably it is facing a high risk of disappearing due to increased temperature and drought associated with the climate change forecast. In order to understand the physiological mechanisms in the adaptation of this species to environmental stress conditions and define management options for the conservation and restoration of its natural populations, we studied the variation in carbon isotope composition (δ¹³C) and in the relative growth rate (RGR) in plants of six populations of P. pinceana subjected to water stress and high temperature under greenhouse conditions. The study populations represented a north-south transect of the natural distribution of the species in Mexico. In a factorial experiment, two temperature environments were tested [without changing the temperature (T₀) and with an increase of 2 °C (T₁) in average temperature] and two levels of humidity [gravimetric content of 50 % (S₀) and 12-20 % (Sj) soil moisture]. Temperature did not influence the value of δ¹³C, but water stress caused a significant reduction in ¹³C discrimination (higher δ¹³C). The effect was greater without stress temperature (T_o). A significant variation among populations was found in δ¹³C values. In the two moisture conditions, the northern populations exhibited greater δ¹³C and higher RGR in height, compared to the southern. The (δ¹³C values of populations were positively correlated with the RGR in height, but not with biomass accumulation. The analysis of results shows that water use efficiency, estimated indirectly through the value of δ¹³C, has an important role in the adaptation capacity of P. pinceana populations to the drought conditions it faces at its natural habitat; it is also possible to identify populations of the species with the possibility to adjust to conditions of greater environmental stress associated with climate change.

Palavras-chave : adaptation; climate change; carbon isotope discrimination; water use efficiency; water stress; relative growth rate.

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