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To help understand leaf hydraulic conductance (Kleaf) modulation under high irradiance, well-watered poplars (Populus trichocarpa Torr. & Gray ex Hook and Populus nigra L.) were studied diurnally at molecular and ecophysiological scales. Transcriptional and translational modulations of plasma membrane intrinsic protein (PIP) aquaporins were evaluated in leaf samples during diurnal time courses. Among the 15 poplar PIP genes, a subset of two PIP1s and seven PIP2s are precociously induced within the first hour of the photoperiod concomitantly with a Kleaf increase. Since expression patterns were cyclic and reproducible over several days, we hypothesized that endogenous signals could be involved in PIP transcriptional regulation. To address this question, plants were submitted to forced darkness during their subjective photoperiod and compared with their control counterparts, which showed that some PIP1s and PIP2s have circadian regulation while others did not. Promoter analysis revealed that a large number of hormone, light, stress response and circadian elements are present. Finally, involvement of aquaporins is supported by the reduction of Kleaf by HgCl2 treatment.

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High-input agriculture has been associated with a drastic reduction of within-field crop genetic diversity, while plant (mostly functional) diversity in natural ecosystems has been shown to promote ecosystem functioning. Increasing intra-specific diversity in agroecosystems is a promising strategy to stabilize crop productivity and promote the associated diversity of fauna and microbiota. We investigated the effect of the within-field diversity of bread wheat varieties on arbuscular mycorrhizal fungi (AMF) and two enzymatic activities involved in organic nitrogen and phosphorus mineralization. A field experiment was designed to test whether the number of mixed wheat varieties in a plot, or their functional diversity (previously assessed), influence the abundance and diversity of AMF and the activity of leucine aminopeptidases and phosphatases in the root zone. The AMF abundance was measured by quantitative polymerase chain reaction, community composition was analyzed by Illumina metabarcoding on two AMF specific markers, and potential microbial activities were quantified by biochemical assays. Wheat traits related to root morphology and susceptibility to fungal diseases previously quantified for each variety were also used. Number of varieties significantly increased AMF abundance in roots, whereas functional cluster number did not, with no impact of root morphology. Functional cluster number influenced AMF diversity, though weakly and not linearly, responding most to binary mixtures. Both wheat variety and functional group number increased the potential leucine amino-peptidase activities in the root zone, while no effect was observed for phosphatase activities. Our results highlight that increasing crop intra-specific diversity triggered changes in key processes involved in nutrient acquisition.

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