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Plant function arises from a complex network of structural and physiological traits. Explicit representation of these traits, as well as their connections with other biophysical processes, is required to advance our understanding of plant-soil-climate interactions. We used the Terrestrial Regional Ecosystem Exchange Simulator (TREES) to evaluate physiological trait networks in maize. Net primary productivity (NPP) and grain yield were simulated across five contrasting climate scenarios. Simulations achieving high NPP and grain yield in high precipitation environments featured trait networks conferring high water use strategies: deep roots, high stomatal conductance at low water potential (“risky” stomatal regulation), high xylem hydraulic conductivity, and high maximal leaf area index. In contrast, high NPP and grain yield was achieved in dry environments with low late-season precipitation via water conserving trait networks: deep roots, high embolism resistance, and low stomatal conductance at low leaf water potential (“conservative” stomatal regulation). We suggest that our approach, which allows for the simultaneous evaluation of physiological traits and their interactions (i.e., networks), has potential to improve crop growth predictions in different environments. In contrast, evaluating single traits in isolation of other coordinated traits does not appear to be an effective strategy for predicting plant performance.Summary statementOur process-based model uncovered two beneficial but contrasting trait networks for maize which can be understood by their integrated effect on water use/conservation. Modification of multiple, physiologically aligned, traits were required to bring about meaningful improvements in NPP and yield.

The influence of photosynthetically active radiation (PAR) on endogenous phytohormone concentrations of a heterocystous N-fixing Anabaena sp. cyanobacterium was studied under 14-day batch cultivation at the CSU Horticultural Research Farm during 2016. The two-factorial experiment compared phytohormone concentrations in 52-L Anabaena sp. cultures grown in CO2-supplemented Allen and Arnon N-free growth medium within and outside polyethylene-covered high tunnels. Inoculation densities were designed to capture 91% and 84% of day 1 maximum outdoor PAR. Across two trials, LC-MS/MS analysis detected mean concentrations of 0.137 ± 0.062 (standard deviation) ng mg−1 dry weight (dw) abscisic acid (ABA), 0.189 ± 0.049 ng mg−1 dw indole-3-acetic acid (IAA), 0.134 ± 0.048 ng mg−1 dw indole acetamide (IAM), 0.116 ± 0.032 ng mg−1 dw indole carboxylic acid (ICA), and 0.022 ± 0.017 ng mg−1 dw trans-zeatin riboside (tZr). Salicylic acid (SA) was detected at significantly different concentrations of 0.449 ± 0.229 ng mg−1 dw in trial 1 and 1.066 ± 0.262 ng mg−1 dw in trial 2. ICA and SA have not been reported as cyanobacterial metabolites. Regression equations based on treatment variables and production parameters found that solar irradiance, likely through light stress or energy availability, was a significant variable in predicting ABA, IAA, IAM, and SA concentrations. Anabaena sp. culture inoculation density was determined to be a significant variable in predicting IAA, IAM, and SA concentrations. IAA and SA concentrations were comparable to those reported to have beneficial effects on plant growth when applied as a constituent of cyanobacterial biomass.

Root pressure, also manifested as profusive sap flowing from cut stems, is a phenomenon in some species that has perplexed biologists for much of the last century. It is associated with increased crop production under drought, but its function and regulation remain largely unknown. In this study, we investigated the initiation, mechanisms, and possible adaptive function of root pressure in six genotypes of Sorghum bicolor during a drought experiment in the greenhouse. We observed that root pressure was induced in plants exposed to drought followed by re-watering but possibly inhibited by 100% re-watering in some genotypes. We found that root pressure in drought stressed and re-watered plants was associated with greater ratio of fine: coarse root length and shoot biomass production, indicating a possible role of root allocation in creating root pressure and adaptive benefit of root pressure for shoot biomass production. Using RNA-Seq, we identified gene transcripts that were up- and down-regulated in plants with root pressure expression, focusing on genes for aquaporins, membrane transporters, and ATPases that could regulate inter- and intra-cellular transport of water and ions to generate positive xylem pressure in root tissue.