A root is a root is a root? Water uptake rates of Citrus root orders

Abstract

Knowledge about the physiological function of root orders is scant. In this study, a system to monitor the water flux among root orders was developed using miniaturized chambers. Different root orders of 4-year-old Citrus volkameriana trees were analysed with respect to root morphology and water flux. The eight root orders showed a broad overlap in diameter, but differences in tissue densities and specific root area (SRA) were clearly distinguishable. Thirty per cent of the root branch biomass but 50% of the surface area (SA) was possessed by the first root order, while the fifth accounted for 5% of the SA (20% biomass). The root order was identified as a determinant of water flux. First-order roots showed a significantly higher rate of water uptake than the second and third root orders, whereas the fourth and fifth root orders showed water excess. The water excess suggested the occurrence of hydraulic redistribution (HR) as a result of differences in osmotic potentials. We suggest that plants may utilize hydraulic redistribution to prevent coarse root desiccation and/or to increase nutrient acquisition. Our study showed that the novel 'miniature depletion chamber' method enabled direct measurement of water fluxes per root order and can be a major tool for future studies on root order traits.

Plant Water Uptake in Drying Soils

“…Because embolized vessels are not hydraulically conductive, the flow of water through the root segment is restricted to the remaining, noncavitated vessels. Different species are not equally susceptible to cavitation (Cochard et al, 2008) or even cultivars (Cochard et al, 2007a;Li et al, 2009;Rewald et al, 2011), but not always (Lamy et al, 2014). Susceptibility to cavitation has been linked to the large xylem vessels, anatomy of walls, and pits (Delzon et al, 2010;Herbette and Cochard, 2010;Christman et al, 2012).…”

Maintaining connectivity: understanding the role of root order and mycelial networks in fine root decomposition of woody plants

“…1; Guo et al 2004;Hishi 2007;Long et al 2013;Jia et al 2013). Lower order roots are involved in water and nutrient uptake and have higher rates of respiration due to increased metabolic activity (Valenzuela-Estrada et al 2008;Xia et al 2010;Rewald et al 2011;Jia et al 2013). As a result, lower order roots contain higher concentrations of N and lower concentrations of total non-structural carbohydrates (TNC; Fan and Guo 2010).…”

It’s Complicated: Intraroot System Variability of Respiration and Morphological Traits in Four Deciduous Tree Species

“…However, within branched systems of single-root units, a distinct heterogeneity of root traits is also present, especially in but not limited to woody root systems (Rewald et al, 2011). Thus, a key to the understanding of the functioning of root systems is knowledge of the traits of individual root segments, especially those related to water and nutrient uptake as well as carbon invested.…”