Rapid adjustment of root growth and rhizosphere interactions to localized water and nutrient enrichment

Yan, Jing and Bogie, Nathaniel A. and Ghezzehei, Teamrat A.

Manuscript in preparation, vol. , 2019.

Abstract

Spatial availability of water and nutrient is known to affect plant root growth, rhizosphere interactions and plants are capable of integrating this spatial information to proceed the optimization of essential resource uptake; however, plants’ perception of and feedbacks to nutrient enrichment, especially in dry soil patches, has not been fully understood. Here we reveal that spatial segregation of water and nutrient across different portions of root systems create spatial signals that determine the physiological adjustment of root proliferation and rhizosphere water potential fluctuations. We show that plants are able to extract significant amounts of nutrients from the drier but nutrient-rich regions facilitated by root growth and internal exchange of water through root systems from the wet but nutrient-deficient regions. In contrast to previous findings, our results suggest that this environmental response is not fully passive and requires available nutrients to induce root production and water potential fluctuation. Scanning electron microscope images of rhizosheath demonstrate that such responses are likely mediated by plants’ self-regulation of root morphology and rhizosphere pore structure at the local scales. Using rhizosphere water potential monitorization, we show that the internal water exchange increases as root establishment proceeds and its increase in magnitude likely reflects the increasing extent of rhizosphere hydraulic connectivity. Overall, higher nutrient availability induces the alteration of root structure/morphology and rhizosphere hydraulic properties, both of which in turn are necessary for enhancing nutrient accessibility in relatively dry soil patches. Our work suggests that multiple level of information, i.e. both the spatial availability of water and nutrient, is sensed and processed for responses of root growth and rhizosphere interactions and these localized responses largely regulate the plant performance especially under unfavorable growing conditions.

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