Purpose: In a complex soil environment, competitive and environmental factors will interact with individual traits to in uence a plant's root growth patterns and ability to compete for resources. Here, we examine how root growth of a focal plant, Plantago lanceolata L., responds to resource heterogeneity and to presence of two neighbor species, Centaurea jacea L.and Poa pratensis L. Methods: A full factorial experiment tested the effects of nutrient heterogeneity, neighbors, and their interaction on root responses of Plantago. Roots in shared quadrants of a pot were harvested and quanti ed by qPCR for plants grown alone or with a neighbor, in patchy or even soil. The effects of experimental treatments on Plantago root mass distribution were tested with two-way ANOVA.Results: When soil resources were evenly distributed, Plantago individuals increased root allocation to soil shared with a Centaurea neighbor but not a Poa neighbor. When soil resources were patchy, Plantago responded more strongly to Poa than to Centuarea, and placed more roots in the high-resource patch.Conclusions: These results demonstrate that plants can respond differently to neighbors depending on species and that integrating multiple cues results in non-additive effects on root behavior.
The nitrogen‐fixing, non‐heterocystous cyanobacterium Hydrocoleum sp. (Oscillatoriales) is a common epiphytic and benthic bloom‐former in tropical and subtropical shallow water systems but shares high phylogenetic similarity with the planktonic, globally important diazotroph Trichodesmium. Multiphasic observations in this study resulted in unexpected identification of Hydrocoleum sp. in mass accumulations in a coastal lagoon in the Western temperate North Atlantic Ocean. Hydrocoleum physiology was examined in situ through measurements of N2 and CO2 fixation rates and expression of genes involved with N2 fixation, CO2 fixation, and phosphorus (P) stress. Bulk N2 fixation rates and Hydrocoleum nifH expression peaked at night and were strongly suppressed by dissolved inorganic nitrogen (DIN). The expression of high affinity phosphate transporter (pstS) and alkaline phosphatase (phoA) genes of Hydrocoleum was elevated during the night and negatively responded to phosphate amendments, as evidence that these mechanisms contribute to P acquisition during diazotrophic growth of Hydrocoleum in situ. This discovery at the edge of the previously known Hydrocoleum habitat range in the warming oceans raises intriguing questions about diazotrophic cyanobacterial adaptations and transitions on the benthic‐pelagic continuum.
Purpose: In a complex soil environment, competitive and environmental factors will interact with individual traits to influence a plant’s root growth patterns and ability to compete for resources. Here, we examine how root growth of a focal plant, Plantago lanceolata L., responds to resource heterogeneity and to presence of two neighbor species, Centaurea jacea L.and Poa pratensis L. Methods: A full factorial experiment tested the effects of nutrient heterogeneity, neighbors, and their interaction on root responses of Plantago. Roots in shared quadrants of a pot were harvested and quantified by qPCR for plants grown alone or with a neighbor, in patchy or even soil. The effects of experimental treatments on Plantago root mass distribution were tested with two-way ANOVA. Results: When soil resources were evenly distributed, Plantago individuals increased root allocation to soil shared with a Centaurea neighbor but not a Poa neighbor. When soil resources were patchy, Plantago responded more strongly to Poa than to Centuarea, and placed more roots in the high-resource patch. Conclusions: These results demonstrate that plants can respond differently to neighbors depending on species and that integrating multiple cues results in non-additive effects on root behavior.
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