Anatomical and hydraulic traits can indirectly and directly measure a root’ transport capacity, respectively. Exploring variation of root traits along topological orders within species is key to understand functional shifts along root architecture and its anatomical underpinnings. However, no study has examined variation in fine root vessel traits along topological orders within and across species.
In a study published in Journal of Experimental Botany, researchers from Xishuangbanna Tropical Botanical Garden (XTBG) and their collaborators investigated the variation of fine root tubular traits in topological order within and across tropical tree species. They also explored how the fine root traits are affected by environmental factors, species characteristics, and ecological niches.
The researchers characterized fine root traits related to cortex, stele and vessels across five topological orders in 80 individual trees of 20 species in Xishuangbanan, China.
They found strong variation of most of the traits studied across root topological orders. In particular, they found a strong increase in theoretical specific xylem hydraulic conductivity(Kth, the most commonly used parameter to study xylem water transport ), mean vessel diameter (MVD) and mean hydraulic diameter (MHD) with increasing root topological orders.
Furthermore, fine root vessel and hydraulic traits show strong covariation patterns among species. Species with thicker fine roots tend to favor hydraulic efficiency rather than safety. MVD and VF were always positively related to Kth across species, which underlines the mechanistic importance of vessel size and fraction in contribution to fine root transport capacity. Within each species, root diameter (RD), stele diameter (SD),and ratio of stele to rot diameter (SDR), and Kth all increased with increasing root topological orders, and Kth had significant positive relationships with RD, SD, and SDR.
The results showed the dominant role of topological order in governing root water transport capacity, reflecting the phenotypic plasticity and structural adaptations of the root xylem in response to varying soil water availability under climate change.
"Our work is one of the first studies to jointly examine the variation and covariation of root vessel traits across a continuous gradient of topological orders. It provides new insight into the variations in fine root anatomical traits and highlights the important role of order-based frameworks in elucidating fine roots hydraulic processes in tropical forest species,” said XIA Shangwen of XTBG.
Contact
XIA Shangwen Ph.D
CAS Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Menglun, Mengla, 666303, China
E-mail: xsw@xtbg.org.cn
Published: 01 March 2024
