Plant, Cell & Environment最新文献

The direct response of stomata to temperature (DRST, the response with the leaf-to-air vapor gradient, Δw, held constant) is poorly studied due to the difficulty of keeping Δw constant while changing leaf temperature. Most published data suggest a positive response, though the mechanisms behind such a response are unknown. We propose that a hydraulic mechanism should contribute to the DRST, wherein temperature decreases the viscosity of water, increasing hydraulic conductance and thereby increasing leaf water potential, which in turn drives stomatal opening. Because the sensitivity of leaf water potential to changes in hydraulic conductance should be proportional to transpiration rate and hence to Δw, this mechanism predicts a stronger positive DRST at higher Δw than at lower Δw. We tested this prediction by measuring the DRST at two different values of Δw, in six diverse angiosperm species. Our results are consistent with the hypothesis that a hydraulic mechanism contributes to the DRST, though the response varies widely across species, and in three of six species the effect of Δw was far stronger than predicted from theory, suggesting a role for other mechanisms in enhancing the effect of Δw on the DRST.

Most Proteaceae and some Fabaceae species produce specialised cluster roots (CRs), and are abundant in severely phosphorus (P)-impoverished soils in southwest Australia. Two types of CRs, compound and simple, have been identified. However, the difference in their P-mining strategies remains unclear. Therefore, we conducted glasshouse and field experiments to compare the P-acquisition strategies among 18 CR-producing species in Proteaceae and Fabaceae. Proteaceae produced a significantly larger mass of CRs than Fabaceae. Particularly, Banksia species produced the largest mass of compound CRs and exhibited the greatest net plant-absorbed P in pots and consistently higher mature leaf manganese concentration in the field. In contrast, Hakea and Grevillea species produced less mass of simple CRs but three times as much soil adhered to their CRs per CR dry weight, resulting in greater absorbed P per CR weight. All plants depleted similar P compounds from soil and accessed c. 52% of P that was not extracted by a NaOH-EDTA solution, suggesting that both CRs shared a common physiological function for mining scarcely available P. This study highlights two divergent P-acquisition strategies: greater biomass investment in compound CRs versus greater P-acquisition efficiency in simple CRs.

Phosphorus (P) is a critical element that limits plant growth in agricultural and natural ecosystems, and its deficiency can significantly reduce wheat yield. We systematically evaluated the response of 296 natural wheat populations to low phosphate (Pi) stress at the seedling stage. Using genome-wide association studies with 190 892 single-nucleotide polymorphism markers, we identified 580 marker-trait associations that exhibited a significant association with low-Pi tolerance coefficients for 18 P use efficiency (PUE) related traits. This analysis revealed 44 multi-environment stable quantitative trait loci (QTLs) and 904 candidate genes. By integrating root transcriptome data from low-Pi tolerant and sensitive genotypes under low-Pi treatment for 3 days, 14 days, and post-Pi resupply for 4 days, we performed weighted gene co-expression network analysis (WGCNA) to identify specific modules associated with PUE. Functional annotation and enrichment analysis identified four hub genes (TraesCS2A03G0333400, TraesCS2A03G0335700, TraesCS4B03G0787300 and TraesCS7D03G0752400) linked to PUE, among which TraesCS4B03G0787300 (TaERF112), a candidate gene for the stable QTL qRDW4B.1. Further validation through expression analysis and gene knockout experiments confirmed that TaERF112 positively regulates low-Pi tolerance in wheat seedlings. This study provides novel insights into the genetic and molecular basis of wheat PUE, offering a foundation for breeding P-efficient wheat varieties that enhance agricultural sustainability.

Xylan is one of the main components of hemicellulose in the wood cell walls of Populus. Low nitrogen (LN) promotes cell wall thickening and hemicellulose biosynthesis in the wood. Glycosyltransferase 43B (GT43B) is a key gene in xylan biosynthesis. However, it remains unclear which specific gene regulates GT43B in xylan biosynthesis in acclimation to LN availability. Here, we report that a previously unrecognized PagMYB057-PagGT43B module regulates xylan biosynthesis in the secondary xylem of P. alba × P. glandulosa in acclimation to LN availability. PagGT43B was highly expressed in the secondary xylem and its expression was induced by LN. The thickness of fiber cell walls and xylan contents were increased in the secondary xylem of PagGT43B-overexpressing poplars compared with those of WT plants under LN conditions, whereas the opposite results were observed in PagGT43B-knockdown poplars compared to those of WT plants. Further molecular analyses revealed that PagMYB057 directly bound to the promoter sequence of PagGT43B to activate its expression. The phenotypes of PagMYB057-overexpressing poplars were similar to those of PagGT43B-overexpressing poplars under LN availability. These results suggest that PagMYB057 activates PagGT43B transcription to enhance xylan biosynthesis in the secondary xylem of P. alba × P. glandulosa in acclimation to LN availability.

Understanding nitrogen (N) isotopic fractionation during plant uptake is critical for interpreting δ¹⁵N variations in terrestrial ecosystems. We investigated isotopic discrimination during ammonium (NH₄⁺) or nitrate (NO₃⁻) uptake in maize (Zea mays) grown hydroponically under controlled conditions with 0.2 and 2 mM to represent high and low affinity transport systems, respectively. Nitrogen (¹⁵ε) and oxygen (¹⁸ε) isotopic fractionation during NO₃⁻ uptake were determined. NO₃⁻ uptake exhibited low and concentration-independent ¹⁵ε values (0.2 mM: ¹⁵ε = −2‰; 2 mM: ¹⁵ε = −1.7‰). In contrast, ¹⁸ε was lower at high concentrations (0.2 mM: ¹⁸ε = −5.3‰; 2 mM: ¹⁸ε = −2.1‰). For NH₄⁺ uptake, ¹⁵ε was higher and increased with concentration (0.2 mM: ¹⁵ε = −5.7‰; 2 mM: ¹⁵ε = −8.5‰). An isotope mixing model suggests a small NO₃⁻ efflux contributes to ¹⁵N and ¹⁸O enrichment in solution due to significant isotopic fractionation during assimilation. The discrimination between source and plant δ¹⁵N is influenced by the source δ¹⁵N, the magnitude of ¹⁵ε, N supply, and uptake kinetics. While plant δ¹⁵N integrates source δ¹⁵N over time, it is unsuitable as a direct tracer. This study refines the understanding of isotopic fractionation mechanisms in plant N uptake and their implications for δ¹⁵N-based ecological investigations.

Kalmia procumbens (K. procumbens), a ubiquitous alpine dwarf shrub, thrives at high elevations, particularly on wind-exposed sites. Plants on contrasting north- and southeast-facing slopes at ~2237 m elevation exhibit differences in leaf colour and growth, suggesting acclimative strategies. Leaves from the southeast-facing slope, exposed to higher leaf temperatures (54°C), stronger winds (21 m ∙ s⁻¹), and increased solar irradiation (2319 µMol photons m⁻² ∙ s⁻¹), developed thicker cuticles (16 µm) than leaves from north-facing slope (11 µm). Raman imaging revealed that cutin and triterpenoids built the foundation in all cuticles on the adaxial and abaxial leaf sides sampled from the two contrasting slopes, while flavonoids accumulated mostly in the outer adaxial cuticle layer and reached the highest values at the N-site. The thicker cuticle of the S-site was mainly composed of cutin and triterpenoids, while the flavonoids were restricted to a thinner outer layer. Minimum diffusive conductance (g_min) was lower in the S-site leaves, which may be associated to their thicker cuticle. The water permeability (g_min) increased exponentially with temperature in leaves from both slopes. Under heat, above 38°C, north-facing leaves with higher flavonoid content lost increasingly more water. While the flavonoids will defend bacterial and fungal pathogens and have a vital role in enhancing plant resilience, they seem to promote higher water permeability of the cuticle of K. procumbens. By combining physiological, structural and chemical insights, our findings suggest that micro-environmental factors play a significant role in driving acclimative responses in K. procumbens. Cuticle structure, composition and function are finely tuned to alpine microhabitats and illustrate a distinct potential for phenotypic adjustment to environmental and biotic constraints.