Green, T. R. | Search bioRxiv

bioRxiv2023

A biochemical analysis of Black Soldier fly (Hermetia illucens) larval frass plant growth promoting activity

Black Soldier fly (Hermetia illucens) larval (BSFL) frass separated from BSFL processed catering waste, and that recovered directly from larvae, was examined for its nitrogen, phosphate and potassium (N:P205:K2O), phytohormone and biogenic amine content, its plant growth promoting activity, and screened to test the hypothesis that bacteria characteristic of the genus Enterococcus, present in the biome of decaying catering waste and the larval gut, pass freely through the gut and are excreted in viable form into their frass. Its plant growth promoting activity was measured by comparing the growth of winter wheat berry (Triticum aestivum) grown in frass treated soil relative to that measured in untreated (control) soil. Its N:P205:K2O, biogenic amine and phytohormone composition were determined by standard soil analysis, HPLC and HPLC/GC-MS methodologies, respectively, and found to be too low to account for its plant growth promoting activity which induced a 11% increase in arial mass and shoot length in treated plants over controls. Colonies of Enterococci grew out on streaking frass collected directly from larvae on standard bile-esculin azide agar culture plates, confirming the hypothesis that viable Enteroccoci are excreted in their frass. Since Enterococci are capable of colonizing the rhizosphere and boosting the growth of plants on amendment into soil, these findings lend further insight into the underlying mechanism(s) accounting for the increased growth of plants growing in frass treated soils.

biochemistry↗

bioRxiv2022

Physiological trait networks enhance understanding of crop growth and water use in contrasting environments

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.

plant biology↗