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    Assessing the impact of agro-industrial olive wastes in soil water retention: Implications for remediation of degraded soils and water availability for plant growth
    (Elsevier Sci Ltd, 2014) Killi, Dilek; Anlauf, Ruediger; Kavdir, Yasemin; Haworth, Matthew
    Olive solid waste (OSW) is a toxic by-product of olive oil production. Disposal of OSW is a major problem in many Mediterranean countries leading to increased interest in its potential as an organic fertiliser. Relatively little is known regarding the impact of augmentation with OSW and olive solid waste compost (OSWC) on soil hydraulic properties. The effect of OSW and OSWC on the hydraulic characteristics of common agricultural soils with high sand but very different silt and clay contents was analysed. Increased organic inputs induced reductions in soil bulk density and increases in air capacity, hydraulic conductivity and the water content available for plant growth (AWC) in the Sandy Clay Loam (SCL) soil. Similar patterns were observed in Loamy Sand (LS) soil augmented with OSW, but OSWC caused reductions in hydraulic conductivity, air capacity and AWC. Nonetheless, over longer timescales OSWC may benefit the hydraulic properties of loamy sand soils as the compost becomes fully incorporated within the soil structure. Augmentation with organic olive waste induced the hydraulic parameters of the sandy clay loam soil to become identical to those loamy sand (LS) with a higher available water capacity; suggesting that soil augmentation with OSW and OSWC may be an effective tool in remediating and improving degraded or organic poor soils. In terms of the improvement of hydraulic parameters, application rates of 6-8% OSW/OSWC were most beneficial for both soil types. (C) 2014 Elsevier Ltd. All rights reserved.
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    COORDINATION OF STOMATAL PHYSIOLOGICAL BEHAVIOR AND MORPHOLOGY WITH CARBON DIOXIDE DETERMINES STOMATAL CONTROL
    (Wiley, 2015) Haworth, Matthew; Killi, Dilek; Materassi, Alessandro; Raschi, Antonio
    Premise of the study: Stomatal control is determined by the ability to alter stomatal aperture and/or the number of stomata on the surface of new leaves in response to growth conditions. The development of stomatal control mechanisms to the concentration of CO2 within the atmosphere ([CO2]) is fundamental to our understanding of plant evolutionary history and the prediction of gas exchange responses to future [CO2]. Methods: In a controlled environment, fern and angiosperm species were grown in atmospheres of ambient (400 ppm) and elevated (2000 ppm) [CO2]. Physiological stomatal behavior was compared with the stomatal morphological response to [CO2]. Key results: An increase in [CO2] or darkness induced physiological stomatal responses ranging from reductions (active) to no change (passive) in stomatal conductance. Those species with passive stomatal behavior exhibited pronounced reductions of stomatal density in new foliage when grown in elevated [CO2], whereas species with active stomata showed little morphological response to [CO2]. Analysis of the physiological and morphological stomatal responses of a wider range of species suggests that patterns of stomatal control to [CO2] do not follow a phylogenetic pattern associated with plant evolution. Conclusions: Selective pressures may have driven the development of divergent stomatal control strategies to increased [CO2]. Those species that are able to actively regulate guard cell turgor are more likely to respond to [CO2] through a change in stomatal aperture than stomatal number. We propose a model of stomatal control strategies in response to [CO2] characterized by a trade-off between short-term physiological behavior and longer-term morphological response.