The relationship between individual root anatomy and fine root system development in blueberry seedlings: dominance of diarch roots in initial root systems

Abstract

Heterogeneity of individual root traits (heterorhizy) is thought to be one of the most important mechanisms that maintain the functional gradients in fine root systems. It is necessary to know heterorhizy and its relation to the root system architecture in seedlings, because it is the initial form of fine root development. Herein, we investigated individual root traits and the root system architecture of blueberry seedlings by using the protoxylem grouping. Most individual roots were diarch but some laterals were monarch. Compared to the monarch, the diarch roots had significantly larger diameters and tissues, and over half of them exhibited secondary growth. In other words, frameworks of the blueberry seedlings were diarch, although those of cuttings had been at least triarch as seen in our previous study. The employment of diarch frameworks may optimize investment for root system expansion of blueberry seedlings. Our results imply ontogenetic dynamics of heterorhizy in blueberries.

Comparative branching order and root anatomy of clonal and seed-grown avocado trees (Persea americana Mill.).

“…Their root areas are mainly occupied by cortical tissue, which is closely associated with nutrient and water absorption from the soil (Pregitzer, 2002;Guo et al, 2008;Wang et al, 2019). Similar results were found by Baba et al, 2019, in the fine roots of blueberry seedlings and cuttings.…”

The Hierarchy of Protoxylem Groupings in Primary Root and Their Plasticity to Nitrogen Addition in Three Tree Species

“…Root length, diameter and stele diameter, as well as hydraulic conductivity significantly positive correlated with the PG number, supporting our first hypothesis. Similarly, some researchers also reported that PG number is strongly and broadly associated with individual root traits in woody (Wilcox, 1962;Horsely and Wilson, 1971; Zadworny and Eissenstat, 2011;Baba et al, 2018), herbaceous (Jackson, 1922;Draye et al, 1999;Mellor et al, 2019) and fern (Wardlaw, 1928) species. Why do root functional traits positively relate to the number of PG?…”

“…The strict hierarchy of PG and root functional traits along developmental order were independent of species and treatments, suggesting the intrinsic mechanism of building stable root systems. Therefore, heterogeneous individual roots would be functionally integrated by PG for a better root classification (Baba et al, 2018(Baba et al, , 2019.…”

“…Hierarchy, Plasticity of Protoxylem Groups individual roots (Baba et al, 2018(Baba et al, , 2019 and even the whole root system (Hishi, 2007;Tawa and Takeda, 2015; Figure 1). For example, PG strongly influences the potential trade-offs of absorption and transportation (Zadworny and Eissenstat, 2011;Bagniewska-Zadworna et al, 2012.…”

“…Therefore, if the root stream order was applied in the PG analysis, which would cause a repetition or overestimation of PG quantity statistics. Alternatively, root developmental order was efficient to describe the PG arrangement across different root architectures (Baba et al, 2018), because it corresponds with the ontogeny of root system (Pregitzer et al, 1997). Specifically, the first-order roots are the original roots, these are the mother/parent roots of finely branched second-order roots, and third-order roots are the daughter roots of the second-order ones (Picon-Cochard et al, 2012).…”