Resumo

CORDOBA-RODRIGUEZ, Diana; VARGAS-HERNANDEZ, J. Jesús; LOPEZ-UPTON, Javier  e  MUNOZ-OROZCO, Abel. Root growth in young plants of Pinus pinceana Gordon in response to soil moisture. Agrociencia [online]. 2011, vol.45, n.4, pp.493-506. ISSN 2521-9766.

Pinus pinceana Gordon is an endemic pinyon pine of México that grows in semiarid conditions, in isolated populations, along the Sierra Madre Oriental. In order to identify root traits associated with mechanisms of adaptation to water stress conditions, the growth and root morphology in two soil moisture conditions were evaluated in plants of six populations of the species representing a geographical gradient of aridity. The study was conducted on 3-yearold plants under greenhouse conditions, maintaining soil moisture near field capacity (S₀) or below 20 % of usable moisture (S₁) over a period of 160 d. The restriction of irrigation reduced by 27 % the number of main roots and 51 % of the root biomass below the 15 cm of soil depth, but increased 166 % the number of lateral roots and 83 % the number of fine growing roots and reduced 30 % the shoot/ root ratio. Populations of the southern region of the species’ natural range, native of sites with lower aridity index were the most affected by drought in the root growth, particularly the length and volume of the root system. This suggests that different environmental conditions to which this pine is subjected in its natural habitat have promoted an ecotypic and genetic differentiation in growth and root structure that can mitigate effects of adverse events such as drought. This ecotypic differentiation is useful in programs for ecological restoration and conservation of the species.

Palavras-chave : weeping piñon pine; drought; adaptation; water stress; biomass distribution; geographic variation.