Root and Agro-Morphological Traits Performance in Cowpea under Drought Stress

Drought is responsible for major yield losses in many worldwide crops and is expected to occur more frequently due to climate change. Cowpea, one of the most drought tolerant legumes, stands as a promising crop in the future climatic context. The screening for genotypes well adapted to this constraint is an essential step to improve cowpea production. A collection of 29 cowpea genotypes (Vigna unguiculata L. Walp.) from the Iberian Peninsula and 11 other countries from worldwide regions was grown and submitted to drought stress using pipes with 30 cm (control) and 90 cm (stress) of height in which water was supplied through the bottom. A set of root and agro-morphological parameters were evaluated, including shoot and root dry weight, root:shoot ratio and stem greenness. Overall, results show that under drought stress, plants seem to invest in root development and reduce shoot biomass. Higher root dry weight under drought conditions could be related to a higher drought tolerance in cowpea. Based on the evaluated traits, it was possible to identify genotypes, particularly C47 (Iran), C56 and C11 (Portugal), which might represent promising cowpea genetic resources for improved drought tolerance breeding.

Wind intensity affects fine root morphological traits with consequences for plant-soil feedback effects

Wind influences the development, architecture and morphology of plant roots and may modify subsequent interactions between plants and soil (plant–soil feedbacks—PSFs). However, information on wind effects on fine root morphology is scarce and the extent to which wind changes plant–soil interactions remains unclear. Therefore, we investigated the effects of two wind intensity levels by manipulating surrounding vegetation height in a grassland PSF field experiment. We grew four common plant species (two grasses and two non-leguminous forbs) with soil biota either previously conditioned by these or other species and tested the effect of wind on root:shoot ratio, fine root morphological traits as well as the outcome for PSFs. Wind intensity did not affect biomass allocation (i.e. root:shoot ratio) in any species. However, fine-root morphology of all species changed under high wind intensity. High wind intensity increased specific root length and surface area and decreased root tissue density, especially in the two grasses. Similarly, the direction of PSFs changed under high wind intensity in all four species, but differences in biomass production on the different soils between high and low wind intensity were marginal and most pronounced when comparing grasses with forbs. Because soils did not differ in plant-available nor total nutrient content, the results suggest that wind-induced changes in root morphology have the potential to influence plant–soil interactions. Linking wind-induced changes in fine-root morphology to effects on PSF improves our understanding of plant–soil interactions under changing environmental conditions.

Plant performance of enhancing licorice with dual inoculating dark septate endophytes and Trichoderma viride mediated via effects on root development

This study aimed to assess whether licorice (Glycyrrhiza uralensis) can benefit from dual inoculation by Trichoderma viride and dark septate endophytes (DSE) isolated from other medicinal plants. We investigated the influences of three DSE (Paraboeremia putaminum, Scytalidium lignicola, and Phoma herbarum) isolated from other medicinal plants on the performance of licorice at different T. viride densities (1×106, 1×107, and 1×108 CFU/mL). Three DSE strains could colonize the roots of licorice, and they established a positive symbiosis with host plants depending on DSE species and T. viride densities. Inoculation of Paraboeremia putaminum increased the root biomass, length, surface area, and root:shoot ratio. Scytalidium lignicola increased the root length, diameter and surface area and decreased the root:shoot ratio. Phoma herbarum increased the root biomass and surface area. T. viride increased the root biomass, length, and surface area. Structural equation model (SEM) analysis showed that DSE associated with T. viride augmented plant biomass and height, shoot branching, and root surface area. Variations in root morphology and biomass were attributed to differences in DSE species and T. viride density among treatments. Paraboeremia putaminum or Phoma herbarum with low- or medium T. viride density and S. lignicola with low- or high T. viride density improved licorice root morphology and biomass. Our findings support the viewpoint that non-host DSE enhanced the root growth of the host plant under different densities T. viride conditions and may also be used to promote the cultivation of medicinal plants.

Metabolic Regulation and Development of Energy Cane Setts upon Auxin Stimulus

Energy cane is a bioenergy crop with an outstanding ability to bud sprouting and increasing yield in ratoon cycles even in marginal lands. Bud fate control is key to biomass production and crop profits due to vegetative propagation and tiller dependency, as well as phenotype plasticity to withstand harsh environmental conditions. During the establishment stage (plant cane cycle), energy cane has a tendency for low root:shoot ratio, which might hamper the ability to cope with stress. Auxin is known to modulate bud sprouting and stimulate rooting in sugarcane. Hence, we treated a slow and a fast bud sprouting energy cane cultivars with auxin or controls (with and without water soaking) for 6 h prior to planting and evaluate plant growth parameters and metabolic profiling using two techniques (gas chromatography with time-of-flight mass spectrometer and nuclear magnetic resonance) to characterize the effect and identify metabolite markers associated with bud inhibition and outgrowth. Auxin inhibited bud burst and promote rooting in setts changing the root:shoot ratio of plantlets. Metabolome allowed the identification of lactate, succinate and aspartate family amino acids as involved in bud fate control through the potential modulation of oxygen and energy status. Investigating environmental and biochemical factors that regulate bud fate can be incremental to other monocot species. Our study provides new insights into bud quiescence and outgrowth in cane hybrids, with the potential to leverage our understanding of yield-related traits, crop establishment and adaptation to global climate change.

Effects of Drought on the Phenology, Growth, and Morphological Development of Three Urban Tree Species and Cultivars

: Under changing climatic conditions, drought may become a critical constraint for trees in urban areas, particularly at roadsides and highly paved squares. As healthy urban trees have proven to be an important mitigation and adaptation tool for climate change as well as a significant provider of ecosystem services, there is a need for planting species and cultivars capable of coping with the limited water supply. However, data on species’ and cultivars’ response to drought, particularly their water supplying root systems remains rare. To consider the whole plant responses to drought situations, we studied the growth and phenology of three frequently planted tree species and cultivars with a diameter of 5–6 cm during a one-year rainfall exclusion experiment conducted in a nursery field as well as the dry biomass of the compartments branch, stem, and root after excavation. Our results revealed that species’ and cultivars’ performance were linked to their within-plant carbon partitioning. A high tolerance to drought was noted for Acer campestre, with a particularly high ratio of root:shoot ratio, which made it presumably less susceptible to droughts. Tilia cordata ‘Greenspire’ was highly affected by the reduced water availability visible through prematurely leaf senescence, while Carpinus betulus ‘Fastigiata’ suffered from losing a considerable part of its root biomass, which resulted in the lowest root:shoot ratio of all species and cultivars. This study demonstrated the need for investigating the reaction patterns of species and cultivars by considering both the above-and the below-ground plant parts. We recommend that, for future tree plantings at harsh and challenging urban sites, an important selection criterion should be species’ and cultivars’ capability to develop and retain strong and dense root systems even under limited water supply, as that is believed to be an important trait for drought tolerance.

Phosphate acquisition efficiency in wheat is related to root:shoot ratio, strigolactone levels, and PHO2 regulation

Higher Pi acquisition efficiency in wheat was related to an improved root system under Pi starvation, allowing higher Pi uptake. This response correlated with faster modulation of the IPS1–miR399–PHO2 pathway and strigolactone levels.

Responses and mechanisms of soil greenhouse gas fluxes to changes in precipitation intensity and duration: a meta-analysis for a global perspective

Although extensive manipulative experiments have been conducted to study the effects of altered precipitation intensity and duration on soil greenhouse gas (GHG; carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) fluxes, the general patterns of GHGs to altered precipitation have not been globally described across biomes. Thus, we performed a meta-analysis of 84 published studies to examine the general responses of CO2, CH4, and N2O fluxes to altered precipitation. Our results indicated that increased precipitation significantly increased N2O emissions (+154.0%) and CO2fluxes (+112.2%) and significantly decreased CH4uptake (−41.4%); decreased precipitation significantly decreased N2O emissions (−64.7%) and CO2fluxes (−8.6%) and significantly increased CH4uptake (+32.4%). Moreover, increased precipitation significantly increased litter biomass and microbial biomass and decreased root biomass and the root:shoot ratio. However, decreased precipitation significantly decreased litter biomass and root biomass and significantly increased root:shoot ratio. These results suggest that precipitation changes could alter the carbon distribution patterns in plants. In addition, the CO2, CH4, and N2O fluxes exhibited diverse responses to different ecosystems, durations of precipitation changes, and changes in precipitation intensity. These results demonstrate that there are many factors that regulate the responses of GHG to precipitation changes.