Catálogo de publicaciones - revistas

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p>A better understanding of plant carbon assimilation, water status and photosystem performance responses to combined heat and drought stress would help to optimize grapevine management under such limiting conditions.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Gas exchange and chlorophyll fluorescence parameters were measured in potted grapevines, cv Sauvignon Blanc, before, during and after simulated six-day heat (T<jats:sub>max</jats:sub> = 40 °C) wave using heated well-watered (HW), heated drought-stressed (HD), non-heated well-watered (CW) and non-heated dry (CD) vines.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Photosynthesis and stomatal conductance in HW vines increased during the morning and dropped in the afternoon with respect to CW vines. Daily plant transpiration in HW almost doubled that of CW vines. When grapevines were already exposed to drought, the effects of the heat wave were negligible, with HD plants showing similar leaf photosynthesis and transpiration to their CD counterparts. Heat, but not drought stress, decreased the maximum (Fv/Fm) and effective photochemical quantum yield of PSII (φPSII), and also affected the use of absorbed energy. HW plants dissipated more radiative energy as heat, a protective mechanism of the photosystem, while HD vines increased the energy dissipated by non-regulated non-photochemical pathways, which might lead to photoinhibition damages. The different behavior could be due to the enhanced transpiration rate and consequent decrease in leaf temperature in HW as compared to HD vines. After the heat wave, only HW vines recovered the afternoon values of photosynthesis, stomatal conductance and φPSII to similar levels as those in CW vines.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Drought had a more significant effect than heat stress on photosynthesis, stomatal conductance and transpiration. The combined heat and drought stress, however, increased the proportion of energy lost by the leaves through harmful non-regulated dissipative pathways. With adequate soil water availability, grapevines withstood the heat wave period through an increase in leaf transpiration, which decreased leaf temperature and protected the PSII from heat damage.</jats:p> </jats:sec>

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Background and aims</jats:title> <jats:p>Below-ground (BG) N of N<jats:sub>2</jats:sub> fixing grain legumes is an important N input to farming systems, likely underestimated as N solely in coarse roots. <jats:sup>15</jats:sup>N methodology can improve measures of BG N accumulation. Our objective was to identify a <jats:sup>15</jats:sup>N method for potential use at remote field sites. We hypothesised that method and frequency of <jats:sup>15</jats:sup>N feeding may result in different estimates of BG N.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>Glasshouse-grown grain legumes, leaf or stem fed <jats:sup>15</jats:sup>N once or twice, were sampled three weeks after feed and at physiological maturity. Three BG fractions were isolated using 2 mm sieving; recovered cleaned roots&gt;2 mm, unrecovered roots &gt;2 mm remaining on sieve with adhering soil, and bulk soil that passed through sieve along with fine roots &lt;2 mm. Fractions were measured for N/<jats:sup>15</jats:sup>N to estimate BGN. Inorganic, total soluble organic and microbial N/<jats:sup>15</jats:sup>N were also assessed for bulk soil.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>Estimates of BG N were not influenced by method or frequency of <jats:sup>15</jats:sup>N feeding. Recovered root N was 33–55% of estimated plant BG N at physiological maturity. Low amounts of fed <jats:sup>15</jats:sup>N detected as inorganic or soluble organic N (0.1–0.7%) and microbial biomass N (0.2–2.5%) were attributed to rhizodeposition. A large proportion of fed <jats:sup>15</jats:sup>N in bulk soil (51–67%) was present as ‘insoluble’ N attributed to fine roots.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusions</jats:title> <jats:p>A single <jats:sup>15</jats:sup>N stem-feeding at remote field sites should suffice to provide a measure of BG N larger than that N measured in recovered roots on a 2 mm sieve. Little evidence for direct leakage into soil labile N pools of highly labelled <jats:sup>15</jats:sup>N post-feed.</jats:p> </jats:sec>

<jats:title>Abstract</jats:title><jats:sec> <jats:title>Purpose</jats:title> <jats:p>Quantifying the stability of individual plants or their contribution to soil reinforcement against erosion or landslides requires an understanding of the tensile properties of their roots. This work developed a new analytical model to understand the tensile stress–strain behaviour of a single root axis, which is the first to incorporating root anatomical features, in order to reduce the existing uncertainty in predictions.</jats:p> </jats:sec><jats:sec> <jats:title>Methods</jats:title> <jats:p>The root was modelled as a linear elastic stele connected to a surrounding linear elastic cortex by means of a linear elastic stele–cortex interface. By solving for force equilibrium, an analytical solution for the full tensile stress–strain behaviour — including any intermediate brittle failures of the stele, cortex and/or interface — was obtained. This model was compared to tensile tests and laser ablation tomography for maize roots.</jats:p> </jats:sec><jats:sec> <jats:title>Results</jats:title> <jats:p>The new modelling approach demonstrated that the root tensile strength is fully determined by the strength of the stele alone, which was an order of magnitude larger than that of the cortex while also 3–4 times stiffer. The reduction in root stiffness beyond the yield point was linked to continuing fracturing of the cortex and debonding along the stele–cortex interface. A larger proportion of the variation in experimentally measured biomechanical characteristics could be explained compared to root diameter power-law fitting methods typically applied in the literature.</jats:p> </jats:sec><jats:sec> <jats:title>Conclusion</jats:title> <jats:p>Stele and cortex biomechanical properties are substantially different, affecting the tensile behaviour of plant roots. Accounting for these anatomical traits increased the accuracy root biomechanical properties from tensile tests.</jats:p> </jats:sec>