Recent research by F. Curtis Lubbe from the Institute of Botany of the Czech Academy of Sciences.
Although the importance of belowground storage organs in plant life appears clear to many of us, there is still some debate on the exact role and importance of these organs. Some argue that allocation of carbohydrates belowground is largely the storage of surplus when plants are otherwise limited by other resources, such as nutrients or water. We tried to trick plants to show us whether they value their carbohydrate storage in a split-pot experiment, where old (oldest and potentially senescing) rhizome portions of plants were placed in drought conditions and the young portions (actively growing forward) in watered conditions and we compared them with the situation where the whole plant/rhizome was in fully-watered conditions.
There were many different ways for these plants to respond, they could 1) increase the rate of rhizome senescence and decrease concentration of storage carbohydrates, 2) halt growth and accumulate access storage carbohydrates belowground, 3) increase concentration of carbohydrate types that can help alleviate drought stress, or 4) move water from the watered rhizome portion to the unwatered (drought stressed) rhizome portion.
Generally, plants preserved their rhizomes and storage carbohydrates. Drought exposed plants had lower concentration of water in their rhizomes, but otherwise there was little response, even when old parts of the rhizome were left unwatered for many months. Even the composition and concentrations of individual types of carbohydrates were left unchanged, indicating that there is an optimal balance among these types preferred by plants. Interestingly, many plants also had live fine roots in the unwatered sections of the pots, perhaps prepared for improving conditions.
There is still much to learn, but for us, the importance of rhizomes is clear: plants need their rhizomes and storage!
For background on this study, see the post in the Function Ecologists blog by the British Ecological Society.
Reference
Lubbe F. C., Bitomský M., Bartoš M., Marešová I., Martínková J., & Klimešová J. (2023). Trash or treasure: Rhizome conservation during drought. Functional Ecology, 37, 2300–2311. https://doi.org/10.1111/1365-2435.14385
Plant Life Belowground 