title: Leaf-to-branch scaling of C-gain in field-grown almond trees under different soil moisture regimes.
abstract: Branch/tree-level measurements of carbon (C)-acquisition provide an integration of the physical and biological processes driving the C gain of all individual leaves. Most research dealing with the interacting effects of high-irradiance environments and soil-induced water stress on the C-gain of fruit tree species has focused on leaf-level measurements. The C-gain of both sun-exposed leaves and branches of adult almond trees growing in a semi-arid climate was investigated to determine the respective costs of structural and biochemical/physiological protective mechanisms involved in the behaviour at branch scale. Measurements were performed on well-watered (fully irrigated, FI) and drought-stressed (deficit irrigated, DI) trees. Leaf-to-branch scaling for net CO2 assimilation was quantified by a global scaling factor (fg), defined as the product of two specific scaling factors: (i) a structural scaling factor (fs), determined under well-watered conditions, mainly involving leaf mutual shading; and (ii) a water stress scaling factor (fws,b) involving the limitations in C-acquisition due to soil water deficit. The contribution of structural mechanisms to limiting branch net C-gain was high (mean fs ∼0.33) and close to the projected-to-total leaf area ratio of almond branches (ε = 0.31), while the contribution of water stress mechanisms was moderate (mean fws,b ∼0.85), thus supplying an fg ranging between 0.25 and 0.33 with slightly higher values for FI trees with respect to DI trees. These results suggest that the almond tree (a drought-tolerant species) has acquired mechanisms of defensive strategy (survival) mainly based on a specific branch architectural design. This strategy allows the potential for C-gain to be preserved at branch scale under a large range of soil water deficits. In other words, almond tree branches exhibit an architecture that is suboptimal for C-acquisition under well-watered conditions, but remarkably efficient to counteract the impact of DI and drought events.
authors: Área de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agronómica, Universidad de Sevilla, Ctra Utrera km 1, 41013 Sevilla, Spain gegea@us.es.
authors: Gregorio
authors: G
authors: Egea
authors: Área de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain.
authors: María M
authors: MM
authors: González-Real
authors: Área de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain.
authors: Bernardo
authors: B
authors: Martin-Gorriz
authors: Área de Ingeniería Agroforestal, Escuela Técnica Superior de Ingeniería Agronómica, Universidad Politécnica de Cartagena, Paseo Alfonso XIII, 48, 30203 Cartagena, Spain.
authors: Alain
authors: A
authors: Baille
mesh_terms: D002244:Carbon / Q000378:metabolism*; D002245:Carbon Dioxide / Q000378:metabolism*; D003681:Dehydration; D008027:Light; D010788:Photosynthesis / Q000502:physiology; D018515:Plant Leaves / Q000502:physiology / Q000528:radiation effects; D018547:Plant Stems / Q000502:physiology / Q000528:radiation effects; D018526:Plant Transpiration / Q000502:physiology; D027861:Prunus / Q000378:metabolism / Q000502:physiology* / Q000528:radiation effects; D012621:Seasons; D012987:Soil / Q000737:chemistry; D014197:Trees; D014867:Water / Q000502:physiology*
chemical_list: D012987:Soil; D014867:Water; D002245:Carbon Dioxide; D002244:Carbon
keywords: Prunus dulcis; carbon balance; deficit irrigation; photosynthesis; productivity; water stress