Root morphology and exudate availability are shaped by particle size and chemistry in Brachypodium distachyon

• DOI: 10.1002/pld3.207
• Publication Date: 2020-07-02T07:46:17Z
• Authors: Joelle Sasse; Suzanne M. Kosina; Markus de Raad; Jacob S. Jordan; Katherine Whiting; Kateryna Zhalnina; Trent R. Northen
• Keywords: 0301 basic medicine; 550; Plant Biology; 580 Plants (Botany); Pseudomonas fluorescens; 1301 Biochemistry, Genetics and Molecular Biology (miscellaneous); root exudation; 03 medical and health sciences; 10126 Department of Plant and Microbial Biology; 1110 Plant Science; Genetics; 10211 Zurich-Basel Plant Science Center; root morphology; particle chemistry; Original Research; 580; Plant biology; 2. Zero hunger; Brachypodium distachyon; Botany; Biological Sciences; particle size; 15. Life on land; 6. Clean water; 1105 Ecology, Evolution, Behavior and Systematics; QK1-989; rhizosphere; 2303 Ecology

AbstractRoot morphology and exudation define a plants’ sphere of influence in soils. In turn, soil characteristics influence plant growth, morphology, root microbiome, and rhizosphere chemistry. Collectively, all these parameters have significant implications on the major biogeochemical cycles, crop yield, and ecosystem health. However, how plants are shaped by the physiochemistry of soil particles is still not well understood. We explored how particle size and chemistry of growth substrates affect root morphology and exudation of a model grass. We grew Brachypodium distachyon in glass beads with various sizes (0.5, 1, 2, 3 mm), as well as in sand (0.005, 0.25, 4 mm) and in clay (4 mm) particles and in particle‐free hydroponic medium. Plant morphology, root weight, and shoot weight were measured. We found that particle size significantly influenced root fresh weight and root length, whereas root number and shoot weight remained constant. Next, plant exudation profiles were analyzed with mass spectrometry imaging and liquid chromatography–mass spectrometry. Mass spectrometry imaging suggested that both, root length and number shape root exudation. Exudate profiles were comparable for plants growing in glass beads or sand with various particles sizes, but distinct for plants growing in clay for in situ exudate collection. Clay particles were found to sorb 20% of compounds exuded by clay‐grown plants, and 70% of compounds from a defined exudate medium. The sorbed compounds belonged to a range of chemical classes, among them nucleosides, organic acids, sugars, and amino acids. Some of the sorbed compounds could be desorbed by a rhizobacterium (Pseudomonas fluorescens WCS415), supporting its growth. This study demonstrates the effect of different characteristics of particles on root morphology, plant exudation and availability of nutrients to microorganisms. These findings further support the critical importance of the physiochemical properties of soils when investigating plant morphology, plant chemistry, and plant–microbe interactions.