Date Published: May 1, 2019
Publisher: Public Library of Science
Author(s): Hongfeng Wang, Zhengquan Wang, Xueyun Dong, Tobias Isaac Baskin.
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.
Owing to unique trait patterns [1, 2], more than 22% of the net primary productivity of global terrestrial ecosystems is transferred below ground annually via fine root turnover , even though the fraction of live fine root biomass to total tree biomass only ranges from less than 1% in mature forests to over 15% in young forests .Recognizing that there is a close association between anatomical characteristics and physiological and ecological functions, researchers have for many years classified fine roots on the basis of anatomical traits . Since then, additional details have been revealed that have allowed us to understand many physiological functions and ecological processes through anatomical traits.
The traits that indicate transport ability were always similar among groups, but the traits that indicate absorptive capacity differed greatly. The shift in function was the main factor that influences the anatomy of fine roots. Some traits show large variation within groups, but the variations in other traits were small. The traits indicate lower-order roots (absorbing roots) were the first 1 or 2 root order in ferns, the first 2 or 3 orders in eudicot herbs, the 1st (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 were higher-order roots (transport roots).