RESUMO
Cortical lacunae caused by drought, especially observed in hybrids originating from Vitis rupestris, disrupt the connection between roots and soil. Yet, the physiological processes behind lacuna formation during drought and its consistency across Vitis species remain unclear. Here, we used a root pressure probe to investigate fine root hydraulic and mechanical properties, in the arid-adapted R-65 and drought-susceptible 101-14Mgt cultivars. We then performed P-V curves, root sap osmolality, and electrolyte leakage (EL) and used fluorescent light microscopy techniques. Only 101-14Mgt showed lacunae formation during drought due to its stiffer cortical tissue, unlike R-65. Lacunae resulted in a notable decline in root hydraulic conductivity during severe drought, with increased EL and root sap osmolality, indicating potential cellular damage. R-65 displayed different and xerophyte-like characteristics featuring a higher turgor loss point and decreased root capacitance, essential for maintaining root structural integrity in arid conditions. Our findings highlight lacuna formation is impacted by root tissue elasticity possibly linked to specific Vitis species favoring deeper rooting. In arid-adapted grapevines, hydraulic regulators such as reduced turgor loss point, and root capacitance could contribute to enhanced drought tolerance.
RESUMO
Erosion and tillage changes negatively the soil physical structure, which directly impacts agricultural systems and consequently food security. To mitigate these adverse modifications, different polymeric materials from synthetic and natural sources, have been used as soil conditioners to improve the hydro-mechanical behavior of affected soils. One of the most interesting and used natural polymers is the alginate hydrogel. Although commercially available alginate hydrogels are primarily sourced from algal, they can also be sourced from bacteria. The gelation capacity of these hydrogels is determined by their molecular properties, which, in turn, are influenced by the production conditions. Bacterial alginate hydrogel production offers the advantage of precise control over environmental conditions during cultivation and extraction, thereby maintaining and enhancing their molecular properties. This, in turn, results in higher molecular weight and improved gelation capacity. In this study, we compared the effects of bacterial alginate (BH) and algal alginate (AH) hydrogels over the mechanical, hydraulic, and structural behavior of coarse quartz sand as a model soil. Mechanically, it was observed that the treatment with the lowest concentration of bacteria alginate hydrogel (BH1) reached higher values of yield strength, Young's modulus (E), shear modulus (G) and strain energy (U) than those treatments with algal alginate hydrogel (AH). Furthermore, the increase in the aggregate stability could be associated with the improvement of mechanical parameters. On the other hand, a greater water retention capacity was observed in the BH treatments, as well as a greater decrease in hydraulic conductivity with respect to the AH and control treatments. All these changes could be explained by the formation of bridge-like structures between the sand particles and the hydrogel, and this alteration may result in a shift in the mechanical and wettability characteristics of the treated soils. Finally, our findings emphasize the superior impact of bacterial alginate hydrogel on enhancing the mechanical and hydraulic properties of coarse quartz sand compared to traditional algal alginate. Besides, the use of bacterial alginate hydrogel could be useful to counteract erosion and water scarcity scenarios in agricultural systems.