Plant-earthworm interactions: influence of age and proportion of casts in the soil on plant growth, morphology and nitrogen uptake
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Background and aims
Earthworms effect on plant growth is mediated by their dejections or “casts”, a complex mixture of organic matter, minerals and microbes. In casts, different processes such as organic matter mineralization and signal molecule production follow a complex temporal dynamics. An adaptation of root morphology to cast dynamics could allow an efficient nitrogen capture by the plant.
The plant Brachypodium distachyon was grown in a laboratory experiment with different proportions of casts of increasing ages. Casts were labelled with 15N to quantify the plant N uptake from the casts. Plant biomass and morphology, especially root system structure, were analysed.
The age of casts had an effect on fine root length, highlighting the importance of the dynamics of cast maturation in root adaptation. Plant biomass production was affected by the interaction between the age and proportion of casts. A positive correlation between the 15N proportion in plant tissues and plant biomasses indicated that plants were more efficient in foraging N in casts than in the bulk soil.
Our results suggested that both a timely adaptation of the root system structure and a significant proportion of casts are necessary to observe a positive effect of casts on plant growth.
KeywordsBiomass production Cast Earthworm Nitrogen cycle Plant development Root morphology
We thank Christelle Ngueda for the technical help and Beatriz Decencière, Amandine Hansart and Florent Massol of the CEREEP - Ecotron IDF/UMS CNRS/ENS 3194 for soil provision. This work was supported by grants from Région Ile-de-France, R2DS 2014-08 and by the French national program CNRS/INSU EC2CO. We are very grateful to Thomas Lerch and Naoise Nunan for their advices regarding the 15N-labeling of earthworm’ casts.
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