Anatomical structures of fine roots of 91 vascular plant species from four groups in a temperate forest in Northeast China

Abstract

Fine roots of plants play an important role in terrestrial ecosystems. There is a close association between the anatomical characteristics and physiological and ecological functions of plants, but we still have a very limited knowledge of anatomical traits. For example, (1) we do not know if herbs and grasses have anatomical patterns similar to those of woody plants, and (2) the variation among different woody plants in the same ecosystem is unclear. In the present study, we analysed the anatomical structures of the fine root systems of various groups of vascular plants (ferns, eudicot herbs, monocots and woody plants) from the same ecosystem (a natural secondary forest on Mao'er Mountain, Heilongjiang, China) to answer the following questions: (1) How does the anatomy of the fine roots change with root order in various plant groups in the same ecosystem? (2) What is the pattern of variation within group? The results show that anatomical traits can be divided into 3 categories: traits that indicate the root capacity to transport resource along the root (stele diameter, xylem cell diameter and xylem cell area); traits that indicate absorptive capacity cortical thickness, (the number of cortical cell layers and the diameter of cortical cells); and traits that are integrated indicators (diameter and the stele to root diameter ratio). The traits indicate the root capacity to transport resource along the root order is generally similar among groups, but absorptive capacity is very different. The shift in function is the main factor influencing the fine root anatomy. Some traits show large variation within groups, but the variations in other traits are small. The traits indicate that the lower-order roots (absorbing roots) in distinct groups are of the first one or two root order in ferns, the first two or three orders in eudicot herbs, the first (only two root orders) or first two orders (more than three root orders) in monocots and the first four or five root orders in woody plants and the other roots are higher-order roots (transport roots). The result will helpful to understand the similarities and differences among groups and the physiological and ecological functions of plant roots.

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

“…The first-and second-order roots in the clonal and seedling root systems exhibited primary growth. 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.…”

“…Recent studies have shown that fine roots, or lowerorder roots, are characterized by the presence of a living parenchymatous cortex and commonly have a smaller diameter and length (Pregitzer et al, 2002;Wang et al, 2019), higher specific root area and specific root length (Wang et al, 2006), lower stele to root diameter ratio (Gu et al, 2014), higher mycorrhizal colonization rate (White et al, 2013;Chen et al, 2016), higher N concentration (Pregitzer et al, 2002;Bowsher et al, 2016), lower C (also cellulose) concentration (Guo et al, 2004), and greater absorption ability (Rewald et al, 2011;McCormack et al, 2015) than other root types. For many species, the major anatomical difference between branching orders is the presence or absence of secondary xylem, which is tightly linked to the root absorption and transport functions (Esau, 1977;Eissenstat & Anchor, 1999;Hishi, 2007).…”

Comparative root anatomy and root bud development after injury in two perennial herbs

“…2014; Wang et al . 2019). In sprouters, the roots tend to be thicker (Goss 1977; Fitter 1991) and capable of storing water and nutrient reserves (Kummerow 1982; Bell et al .…”

Drying of fibrous roots strengthens the negative power relation between biomechanical properties and diameter

“…In particular, initial water loss and diameter shrinkage in woody roots may be limited to cortical and bark tissues (e.g., periderm and senescent cortex), which are known to have negligible mechanical contribution in woody roots (Hathaway and Penny, 1975). The larger cortex to stele ratio of fibrous roots, compared with woody roots (Wang et al 2019), may result in more shrinking and swelling given the susceptibility of cortical tissues to moisture variation (Berry and Roderick, 2005;Gall et al 2002). For instance, seasonal and diurnal variation in root water status could significantly affect diameter of roots growing in soil.…”