No abstract

Belowground carbon (C) dynamics of terrestrial ecosystems play an important role in the global C cycle and thereby in climate regulation. Globally, land-use change is a major driver of changes in belowground C storage. The emerging bioenergy industry is likely to drive widespread land-use changes, including the replacement of annually tilled croplands with perennial bioenergy crops, and thereby to impact the climate system through alteration of belowground C dynamics. Mechanistic understanding of how land-use changes impact belowground C storage requires elucidation of changes in belowground C flows; however, altered belowground C dynamics following landuse change have yet to be thoroughly quantified through field measurements. Here, we show that belowground C cycling pathways of establishing perennial bioenergy crops (0-to 3.5-year-old miscanthus, switchgrass, and a native prairie mix) were substantially altered relative to row crop agriculture (corn-soy rotation); specifically, there were substantial increases in belowground C allocation (>400%), belowground biomass (400-750%), root-associated respiration (up to 2,500%), moderate reductions in litter inputs (20-40%), and respiration in root-free soil (up to 50%). This more active root-associated C cycling of perennial vegetation provides a mechanism for observed net C sequestration by these perennial ecosystems, as well as commonly observed increases in soil C under perennial bioenergy crops throughout the world. The more active root-associated belowground C cycle of perennial vegetation implies a climate benefit of grassland maintenance or restoration, even if biomass is harvested annually for bioenergy production.

Melatonin is a multifunctional signaling molecule, ubiquitously distributed in different parts of plants and responsible for stimulating several physiological responses to adverse environmental conditions. In the current review, we showed that the biosynthesis of melatonin occurred in plants by themselves, and accumulation of melatonin fluctuated sharply by modulating its biosynthesis and metabolic pathways under stress conditions. Melatonin, with its precursors and derivatives, acted as a powerful growth regulator, bio-stimulator, and antioxidant, which delayed leaf senescence, lessened photosynthesis inhibition, and improved redox homeostasis and the antioxidant system through a direct scavenging of reactive oxygen species (ROS) and reactive nitrogen species (RNS) under abiotic and biotic stress conditions. In addition, exogenous melatonin boosted the growth, photosynthetic, and antioxidant activities in plants, confirming their tolerances against drought, unfavorable temperatures, salinity, heavy metals, acid rain, and pathogens. However, future research, together with recent advancements, would support emerging new approaches to adopt strategies in overcoming the effect of hazardous environments on crops and may have potential implications in expanding crop cultivation against harsh conditions. Thus, farming communities and consumers will benefit from elucidating food safety concerns.

No abstract