On August 19, 2025, Professor Kong Deliang and his collaborators from Henan Agricultural University published a research paper entitled "Arbuscular mycorrhizal association regulates global root-seed coordination" in Nature Plants. This study is the first to report the covariant changes in plant root and seed traits on a global scale and reveals the key role of mycorrhizal fungi in root-seed coordination through phosphorus acquisition and pathogen defense.
Effective absorption of soil water and nutrients by roots is fundamental to plant growth, and the construction and function of roots are inseparable from the photosynthetic products provided by leaves. During evolution, the co-evolution of underground roots and aboveground organs has enabled vascular plants to adapt to heterogeneous environments with diverse trait combinations. For example, conserved dimensions of root resources (such as root nitrogen content and root tissue density) are often closely related to leaf economic spectra (such as leaf nitrogen content and specific leaf weight). While we have a deep understanding of the covariation mechanisms between root systems and above-ground organs, the existence of a covariation relationship between root systems and seeds remains a blank slate, with even fewer studies exploring the underlying driving mechanisms.
Terrestrial plants have undergone tremendous changes in morphology and function to adapt to heterogeneous environments. Interspecific differences in absorbing root diameter exceeding 100 times lead to significant differences in their ability to acquire water and nutrients, while interspecific differences in seed quality reach 13 orders of magnitude, significantly differentiating their dispersal and germination. To adapt to environmental changes, these two organs with such significant variations may not be changing independently. Theoretically, root systems and seeds are interconnected in at least two stages of the plant life cycle. During the reproductive stage, seed growth depends on the supply of water and nutrients from the root system. During the seedling stage, the initial development of seedling organs (such as the root system) relies on nutrients stored within the seed. Therefore, elucidating the relationship between absorbing root diameter and seed size is a crucial step in clarifying the root-seed covariant relationship.
Based on the above-mentioned plant reproduction and seedling stages, the researchers proposed the following three mechanisms to explain the formation of root-seed relationships.
Figure 1. Three hypotheses regarding the relationships between roots and seeds. (Yang, et al. 2025)
The research team collected root, stem, leaf, and seed samples from 660 woody plant species in 11 representative forests (covering various climate types from tropical to temperate) from Xishuangbanna, Yunnan to Huzhong, Heilongjiang, China. They measured the traits of each organ, especially the anatomical characteristics of absorber roots (cortex thickness, vessel diameter, and vessel density), and integrated data from the GRooT database and relevant global literature.
The study is the first to reveal that, on a global scale, the average single seed weight of AM plants is significantly positively correlated with the diameter of the absorbing root. More importantly, seed weight is significantly correlated with the thickness of the cortex of the absorbing root, but not with the size of the absorbing root's xylem vessels. In contrast, the absorbing root size of ECM plants is not related to seed weight. Further research reveals that these covariant relationships between roots and seeds are not driven by the material transport function mediated by the root xylem vessels, but are related to the multifunctionality of AM fungi, namely phosphorus absorption and defense against pathogens.
The elucidation of the patterns and mechanisms of synergistic changes between plant roots and seeds provides a completely new perspective on the formation and maintenance of terrestrial plant diversity and has significant application value for agricultural and forestry production practices.
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