Biochemical and physiological responses of Agave species to moisture restriction [Respuestas bioquímico-fisiológicas de especies de agave a la restricción de humedad]
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abstract
Mexico has the greatest richness of Agave species, distributed in diverse environments. In order to contribute to the knowledge on ways to tolerate moisture constraints, the effect of two water potential (Ψ Ψ) in the substrate (-0.7 and-3.5 MPa) on growth, biomass allocation, leaf thickness and proline content in two species of the subgenus Littaea (A. lechuguilla and A. striata), and six of the subgenus Agave (A. americana var. marginata, A. angustifolia subsp. tequilana, A. asperrima, A. cupreata, A. duranguesis and A. salmiana), recognized for its economic and ecological importance, was evaluated during 14 months and under greenhouse conditions. Low moisture inhibited biomass accumulation in the eighth species; despite this, growth (number of leaves and plant coverage) kept in those more adapted to aridity or with broader environmental tolerant limits as A. angustifolia subsp. tequilana, A. duranguensis, A. lechuguilla, and A. salmiana. The limiting Ψ Ψ promoted greater biomass allocation to roots at expense of leaves in some species, and duplication of radical proline in species of the subgenus Agave. The modifi cation of biomass allocation and the increase of proline, as forms to tolerate moisture restriction, presented only in part of the species studied. In contrast, maintaining the thickness of the sheet (indicator of turgidity) was a general reaction to limiting Ψ Ψ. Agave species have diverse physiological and biochemical responses, which refl ect its wide tolerance to adverse environmental conditions and explains the wide ecological distribution of the genus.
