Hydraulic architecture with high root‐resistance fraction contributes to efficient carbon gain of plants in temperate habitats

Abstract

Premise: The hydraulic architecture in the leaves, stems and roots of plants constrains water transport and carbon gain through stomatal limitation to CO 2 absorption. Because roots are the main bottleneck in water transport for a range of plant species, we assessed the ecophysiological mechanism and importance of a high fraction of root hydraulic resistance in woody and herbaceous species. Methods: Biomass partitioning and hydraulic conductance of leaves, stems, and roots of Japanese knotweed (Fallopia japonica, a perennial herb) and Japanese zelkova (Zelkova serrata, a deciduous tall tree) were measured. Theoretical analyses were used to examine whether the measured hydraulic architecture and biomass partitioning maximized the plant photosynthetic rate (the product of leaf area and photosynthetic rate per leaf area). Results: Root hydraulic resistance accounted for 83% and 68% of the total plant resistance for Japanese knotweed and Japanese zelkova, respectively. Comparisons of hydraulic and biomass partitioning revealed that high root-resistance fractions were attributable to low biomass partitioning to root organs rather than high mass-specific root conductance. The measured partitioning of hydraulic resistance closely corresponded to the predicted optimal partitioning, maximizing the plant photosynthetic rate for the two species. The high fraction of root resistance was predicted to be optimal with variations in air humidity and soil water potential. Conclusions: These results suggest that the hydraulic architecture of plants growing in mesic and fertile habitats not only results in high root resistance due to small biomass partitioning to root organs, but contributes to efficient carbon gain.K E Y W O R D S biomass partitioning, Fallopia, high pressure flow meter method, optimal theory, outside of xylem pathway, plant water use, Polygonaceae, Ulmaceae, xylem water transport, Zelkova

Condutância hidráulica e anatomia de vasos do xilema em amoreira-preta

“…O transporte da água por meio da condutância hidráulica a longa distância, pode ser afetado pela presença de embolia no conduto do xilema. Assim, as bolhas de ar formadas nestes condutos deveriam diminuir a condutividade hidráulica dependendo dos elementos ativos do xilema, o processo de recomposição dos condutos, pode ocorrer quando existe uma pressão positiva no xilema, mas também o resultado pode várias dependendo à idade da planta, sendo que as características anatômicas da raiz se desenvolvem e aprofundam no solo, para a absorção de água que encontrar-se mais profunda, sendo que a estrutura radicular mais desenvolvidas tem a capacidade de captação de água mais eficiente (TANEDA et al, 2021).…”