What a difficult life plants have…

The toughest plants are those that are able to grow back from roots or adventitious buds. Not all plants are able to do this; it differs among species and depends on factors such as lifecycle, the age of the plant, and the size of its carbohydrate storage. Previous studies support the idea that plants sprouting vegetatively from roots have an evolutionary advantage, compared with plants germinating from seeds. The reason for this is that growing from a seed often requires very specific conditions. Such plants have to make root buds first and then use their reserves from the unaffected parts for the growth of new leaves. This enables them to create supplies and make seeds.

For such a demanding process to take place, plants need energy. This is stored as saccharides in underground buds, away from sources of disturbance. Seed banks where the seeds are placed are grown in underground rhizomes near leaves or directly on the roots. Seed banks in roots have certain advantages, compared with seed banks on stems. For instance, roots are deeper in the soil, are protected better, and buds can be made anywhere on the root; rhizomes are not typically made in the first year of growth, usually forming in the second year. Notwithstanding these obvious benefits of root buds, they are much rarer and less well studied than stem buds.

Barbarea vulgaris.
We can find this plant all over the world. It grows mainly in sunny places near roads. It can grow up to 0,5 m.
Source: Wikipedia, author: Krzysztof Ziarnek

How can we discover whether a plant is using its storage in the most efficient way and minimising the losses of fitness? The key determinants are the regrowth of leaves, increased root respiration, and maximised rate of photosynthesis. Based on these values, an experiment was designed by a team of scientists from the Charles University Faculty of Science and the Institute of Botany of the Czech Academy of Sciences under the leadership of Jitka Klimešová. They studied the reaction of Barbarea vulgaris to a total shoot biomass removal and assessed whether vegetative regeneration after a disturbance is more advantageous for a plant than seed germination.

After six weeks of plant growth, the aboveground biomass of part of the objects was destroyed and their further evolution was monitored. Root respiration drastically decreased immediately after the disturbance, but levelled up to equal the control objects only three weeks later and was even higher at the end of the measurement period. By contrast, root respiration of the control objects decreased from the third week onwards. Rate of photosynthesis also fell after the injury but was then renewed to equal the level reached by the control plants in two weeks. In contrast to these two factors, there were no signs of compensatory photosynthesis during the experiment, which suggests that plants substituted for their loss by increasing the number of leaves.

During the experiment, injured plants did not completely restore their shoot biomass and were smaller at the end of the study than the control subjects. On the other hand, their growth exactly matched that of the control plants; consequently, six weeks after the injury, the damaged plants equalled the size of the control plants six weeks after germination. Overall, regeneration from roots for this species is only moderately more sufficient than seed germination. However, generative regeneration is dependent on multiple factors, such as temperature or drought, while vegetative regeneration is not as limited and can begin immediately after the injury.

Martínková, J., Hájek, T., Adamec, L., & Klimešová, J. (2021). Growth, root respiration and photosynthesis of a root-sprouting short-lived herb after severe biomass removal. Flora, 284, 151915.

Eliška Leštinová