Jana Martínková (ExFuMo1), Institute of Botany of the Czech Academy of Sciences, discusses her article: The hidden half of ontogeny and seasonal dynamics in perennial herbs
While flowers and leaves capture our attention, the unseen world beneath the soil is just as vital to plant survival and ecological balance. This truth applies not only to acquisitive fine roots, but also to the coarse belowground organs that hold largely untold secrets about persistence and reproduction. Perennial clonal plants rely on robust belowground structures like rhizomes, tubers, and bulbs to regenerate after harsh seasons. These organs store carbohydrates, house buds for regrowth, and support vegetative reproduction. Despite their critical roles, belowground coarse organs (usually represented by rhizomes) remain outsiders in plant ecology and are often overlooked.
Our recent research sought to uncover the dynamics of rhizome development and its relationship to aboveground parts and species’ habitat preferences—a topic that has remained largely uncharted. This three-year study of 20 species of rhizomatous herbs revealed intriguing insights into how these plants balance aboveground and belowground growth strategies.
One of our key findings confirmed that the seasonal development, and also ontogeny, of aboveground and belowground plant parts follows distinct trajectories. Aboveground structures like leaves and stems grow rapidly, driven by seasonal growth demands. In contrast, belowground organs such as rhizomes take longer to develop, often requiring multiple years. This slower pace reflects their perennial nature and long-term investments in carbohydrate storage and clonal propagation. These findings highlight the importance of studying plants as integrated systems, where aboveground and belowground parts are deeply interconnected.
One important role of rhizomes is their storage capacity of carbohydrates like starch, fructans, and many others. This storage serves multiple important purposes, such as providing energy for rapid regrowth and aiding in protection against frost damage. In our study, we examined how phenology – in our case the timing of flowering – influences the development of carbohydrate storage during seasons and plant ontogeny. Early-flowering species generally need large quantities of carbohydrate storage so that they can regrow quickly after freezing winters, exposing them to the risk of cold spells. However, later-flowering species, avoid this risk and thus do not necessarily need such large storage. Although our results are not fully conclusive, early and late-flowering rhizomatous species did exhibit these expected differences in carbohydrate storage strategies, further emphasizing the interplay between growth timing and survival mechanisms.
Our study also assessed whether distinct patterns of rhizomes development affect their seasonal development and ontogeny. There are two morphological and development types of rhizomes: epigeogeneous rhizomes, which start rhizome growth from aboveground and are later pulled belowground, and hypogeogeneous rhizomes, which form entirely belowground. We found that the hypogeogeneous rhizomes had sturdier structures with higher carbon content (C%) in roots and greater dry matter content in both roots and rhizomes than the epigeogeneous rhizomes. These traits likely make them more costly to develop but better adapted for belowground growth from the beginning. Interestingly, the two rhizome types also differ in their reproductive strategies over ontogeny. While species with hypogeogeneous rhizomes preferentially invest in clonal multiplication and belowground organs, species with epigeogeneous rhizomes invest more to aboveground generative reproduction, i.e. flowering and seed production.
By exploring the hidden half of plants, we gain a deeper appreciation for the interconnectedness of aboveground and belowground growth. Rhizomes and other coarse belowground organs reveal strategies that ensure survival, resilience, and reproduction in challenging environments. Our research serves as a reminder that plants are more than what meets the eye and what may be revealed in short term studies. By integrating studies of belowground and aboveground traits, and by letting plants develop their perennating organs, we can unlock a fuller understanding of plant ecology, paving the way for more effective conservation and restoration efforts.
