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Wang et al. recently showed that, in soybean (Glycine max), root nodule formation is induced by a light-triggered signal that moves from the upper part of the plant to the roots. This novel signaling process opens a new area of research aimed to optimize the carbon–nitrogen balance in plant–rhizobium symbiosis. [ABSTRACT FROM AUTHOR]

Plants secreted phytocytokine SMALL PHYTOCYTOKINES REGULATING DEFENSE AND WATER LOSS (SCREWs) and its receptor PLANT SCREW UNRESPONSIVE RECEPTOR (NUT) to counter abscisic acid (ABA)- and pathogen-induced stomatal closure (Liu et al.). This novel signaling process provides plants with a new strategy to increase immunity through disrupting an aqueous habitat for pathogen colonization. [ABSTRACT FROM AUTHOR]

We evaluated the importance of conserved water use in drought adaptation in soybean [ Glycine max (L.) Merr.], and identified the traits involved in this mechanism. Eight soybean genotypes, four landraces and four recent cultivars, were collected and yield performance in the field was determined and used in pot experiments to evaluate the yield performance and the water use pattern under three soil moisture treatments imposed from 40 days after sowing: well-watered [WW, soil water content (SWC) maintained between 85%–100% field capacity (FC)]; water stress (WS, water withheld until SWC decreased to 30% FC, rewatered to 100% FC and water withheld again to 30% FC); and terminal water stress (TWS, water withheld until maturity). The recent cultivars all out-yielded the landraces in two different years in the field and under well-watered conditions in the pot experiment. Among the eight soybean genotypes, J19 and ZH – two recent cultivars with lower daily water use before flowering, but higher use after flowering – had the best yield performance in the WS and TWS treatments in the pot experiment and in the field. These two soybean genotypes and J19, another recent cultivar, had higher grain yield, hundred-grain weights and water use efficiency for grain yield (WUE G ) in the WS treatments than the other genotypes, and higher hundred grain weights, higher WUE G , higher pod numbers and the only significant grain yield in the TWS treatment. J19 and ZH had low root length densities (RLD), low leaf areas at flowering, and transpiration decreased at high plant available soil water content under drought. Thus, we conclude that reducing RLD and restricting water loss contributed to conserved water use and improved yield performance and WUE G in water-limited conditions. [ABSTRACT FROM AUTHOR]

Legume-based intercropping has the potentials for improving nitrogen (N) behavior in semiarid cereal production. Yet, it is unclear how the intercropped legume mediates the fate and benefits of fertilizer N in plastic film mulched cereal field. A two-year field experiment was conducted with cropping patterns, including maize monoculture, soybean monoculture and maize-soybean intercropping, with N levels (0, 180 and 225 kg N ha−1 for maize; 0 and 40 kg N ha−1 for soybean), and with and without plastic film mulching in maize. Both data qualification from the methods of N-difference and 15N isotope tracer confirmed that maize had a great enhancement of NUE when intercropped with soybean. The use of 180 kg N ha−1 with film mulching for intercropped maize resulted in the highest NUE with 61% 15N recovery, 40% N agronomic efficiency and 91 kg grain kg−1 N partial productivity. Under no mulching, intercropped maize with 180 kg N ha−1 had a 28% higher 15N recovery and 43% less 15N loss with 12% more fertilizer 15N allocation into maize grain than monoculture maize with 225 kg N ha−1. To some extent, this effect was amplified by film mulching. Interestingly, film mulching caused an overuse of soil-derived N in maize, and in this regard, an influence of 67.3% was eliminated by soybean-based intercropping. This deficiency of N was compensated by enhancing the use of fertilizer-derived N and soybean-transferred N (30 kg N ha−1) under low-N rate. The intercropping pattern FM180S40, i.e. film mulched maize with 180 kg N ha−1 and soybean with 40 kg N ha−1, had the highest N fertilization efficiency (FNER=1.29) due to the high land use efficiency (LER=1.19) and maize yield (14 Mg ha−1) with less N fertilizer use. Soybean-based intercropping and film mulching sustained a 20% reduction of N fertilizer based on the optimized N level (225 kg N ha−1) for dryland maize. This further induced a great intercropping advantage of N fertilization efficiency via high NUE of maize and positive processes of NUE formation in maize strips. This study highlights the key role of intercropped soybean in boosting N fertilization benefits and reducing N loss in semiarid film-mulched agriculture systems. [Display omitted] • Cereal NUE mechanism in legume-supported intercropping system was studied. • Labelled-15N confirmed the enhancements of maize NUE when intercropped with soybean. • More labelled-15N was translocated into maize grain for higher N fertilizer benefits. • Intercropped soybean significantly declined the overuse of soil-derived N by film mulched maize. • Intercropped soybean reduced fertilizer N loss for film mulched maize under low N conditions. [ABSTRACT FROM AUTHOR]

• Leaf N and leaf traits are key indicators of shifting photosynthesis (A). • Leaf traits explain the eco-physiological strategies to climate changes. • A mass is highly vulnerable to desert grass-shrubland and warm-temperate forest. • Variability in storage-N required for plant/leaf survival and maintenance. • Mass-based A and dark-respiration with N mass showed stronger affinity compared to area-based. Leaf functional traits profoundly impact the function of diverse-biomes under different environmental conditions. Thus, it is urgent to deeply understand how leaf traits and leaf nitrogen (N) develop photosynthesis adaptive-strategies across functional groups and biomes. We compiled information from previous studies on six diverse-biomes under different climates to determine the difference in functional groups (forbs, deciduous-shrubs, deciduous-trees, and evergreen-needle) and related traits: photosynthesis (A mass , A area), dark respiration (dR mass , dR area), N mass , N area , leaf life-span (LL), specific leaf area (SLA), and diffusive conductance (G s). Then, we used non-linear modeling to examine the A-dR responses to leaf N. Among the biomes, desert grass-shrubland (Colorado) and warm temperate forest (South Carolina) had lower A mass , N mass with lower SLA, while humid temperate forest (North Carolina) displayed higher A mass , N mass with higher SLA, indicating that species in desert grass-shrubland and warm temperate biomes adapt conservative strategies while humid temperate species adapt acquisitive strategies for leaf maintenance against limited N and climate conditions. Among functional groups, forbs had higher A mass , dR mass and N mass , deciduous-shrubs and trees had intermediate A mass , dR mass , and N mass , while evergreen-needle had lower A mass , dR mass with lower N mass. Forbs had minimum storage N (A store), deciduous-shrubs and trees had intermediate A store , while evergreen-needle had the highest A store. We concluded that forbs needed a minimum N-investment for leaf maintenance followed by deciduous and evergreen-needle. These results reveal that leaf N and leaf traits support adaptive-strategies for A-dR that regulate leaf maintenance and photosynthesis capacity under limited resources and environmental conditions. [ABSTRACT FROM AUTHOR]

Biological soil crust (BSC) establishment as a nature-based strategy (NbS) may restore the functionality of degraded soils in semiarid agroecosystems. However, this issue is little documented. To address this issue, a BSC-inoculated (broken-skin inoculation, moss) field experiment was conducted in a semiarid alfalfa (Medicago sativa L.) field in 2018 and 2019, with the treatments as follows: 1) conventional flat planting (control), 2) flat planting with BSC inoculation (BSC), 3) ridge-furrow planting (RF) and 4) sectional ridge-furrow planting (SRF). The result showed that compared with the control, alfalfa biomass was evidently increased in BSC, RF and SRF treatments at the second growing season. Relative to the control, the BSC treatment harvested the highest soil total porosity, mean weight diameter, and macroaggregate proportion (>2 mm) (p < 0.05; significantly greater than RF and SRF). Also, the BSC inoculation remarkably improved soil microbial biomass carbon (C) & nitrogen (N), soil organic C and total N by 46%, 35%, 16% and 29% respectively, also significantly greater than RF and SRF (p < 0.05). This phenomenon was tightly correlated with the optimized soil C fractions as affected by the BSC inoculation, since dissolved organic C, oxidizable organic C, particulate organic C, light fraction organic C and heavy fraction organic C were promoted by 17%, 29%, 13%, 40% and 14% in the BSC treatment respectively, relative to the control (p < 0.05). Therefore, the BSC inoculation significantly improved soil quality in alfalfa field. This outcome was closely associated with the increased soil cohesion and microaggregate proportion, and decreased soil C-N ratio under the BSC. The optimized physiochemical properties boosted C mineralization and the utilization of soil C & N by microbial organisms. Therefore, the BSC establishment can act as a promising NbS to conserve the degraded soils in semiarid agroecosystems. [Display omitted] • Biological soil crust (BSC) as nature-based strategy was tested in alfalfa field. • BSC improved stability of soil physical structure relative to flat planting. • BSC significantly enhanced soil liable carbon and microbial carbon & nitrogen. • BSC showed ecological advantages over natural ridge-furrow planting strategies. • BSC is a promising nature-based strategy to restore the degraded semiarid soils. [ABSTRACT FROM AUTHOR]

• ABA is involved in stomatal closure in ferns, gymnosperms and angiosperms. • P type and R type ABA responses occur during dehydration and rehydration in gymnosperms as well as angiosperms. • Increasing and decreasing behaviour of foliar ABA content in angiosperms during dehydration. The variation in stomatal movement across vascular plants in response to abscisic acid (ABA) has received great attention in recent years. This review is an attempt to better understand the role of ABA in the stomatal movement of seed and seedless plants under dehydration and rehydration. Seed plants, i.e., gymnosperms and angiosperms, have two divergent ABA responses, the peaking type (P-type) and rising type (R-type), to induce stomatal closure under sustained drought stress. However, in the case of ferns and lycophytes, stomata of almost all species exhibit insensitive (I-type) behaviour to ABA. Consequently, seed plants have evolved an optimized water use efficiency to improve their succession in terrestrial ecosystems. During rehydration, the recovery of gas exchange is constrained by ABA accumulation under drought in R-type plants and constrained by hydraulics in P- and I-type plants. Thus, future studies should investigate the mechanisms underlying the divergence in stomata in response to ABA, focusing on P-type vs. R-type ABA responses in seed plants, the competition of seed plants, and the interaction between ABA and hydraulic pathways during rehydration. [ABSTRACT FROM AUTHOR]