Stomatal cavity modulates the gas exchange of Sorghum bicolor (L.) Moench. grown under different water levels

Difference in summer heatwave-induced damage between desert native and urban greening plants in an arid desert region

Summer heatwaves have caused a distinct mortality between urban greening and native plants. However, there are insufficient studies revealing the underlying mechanisms. We hypothesized that differentiation in hydraulic traits and their integration cause the varied heatwave-induced damages between the two plant types. To prove it, three desert native species and five urban greening species were selected as the experimental objects. Then, the number of damaged individuals caused by summer heatwaves were investigated based on the 100 individuals for each species. The hydraulic traits (including hydraulic transport, photosynthetic and leaf traits) of 3-5 mature individuals were measured for each species. The comparative analysis (independent sample t test and one-way ANOVA) and the collaborative analysis (Pearson correlation and network analysis) were used to reveal the differences in heatwave-induced damage, hydraulic traits and their integration between urban greening and native plants. Our results showed that the heatwave-induced damage to urban greening plants was larger than that to native species. Water potentials of leaf and branch in pre-dawn and midday, P50, leaf dry matter content, net photosynthetic rate, transpiration rate and stomatal conductance of desert native species were significantly lower than those of urban greening plants (P < 0.05), while twig specific hydraulic conductivity, Huber value, wood density, intrinsic water use efficiency and the specific leaf area showed opposite patterns (P < 0.05). Trait integration of desert native species (0.63) was much higher than greening plants (0.24). Our results indicate that artificial urban greening plants are more susceptible to drought stress caused by heatwaves than native desert species. In the context of global climate change, in order to maintain the stability and function of urban ecosystems in extreme climate, the screening of greening plants should start from the perspective of hydraulics and trait integration, and more native species with strong drought adaptability should be planted.

Differential Leaf-to-Root Movement, Trophic Transfer, and Tissue-Specific Biodistribution of Metal-Based and Polymer-Based Nanoparticles When Present Singly and in Mixture

The transfer of nanoparticles (NPs) through the terrestrial food chain via foliar uptake presents poorly understood risks, especially in scenarios involving copollution and plant translocation. Herein, we exposed the radishes to single and mixed foliar doses of CeO2 NPs and deuterated polystyrene (DPS), investigating the trophic transfer of NPs from radish shoots/roots to snails. Compared to single treatments, mixture treatments increased Ce uptake by plants but had no effect on DPS uptake. Additionally, mixture treatments did not affect the movement of Ce and DPS from shoots to roots. Under NP mixture exposure, trophic transfer efficiencies (TTF) for Ce (2.09 × 10-2) and DPS (2.54 × 10-2) significantly decreased in shoot-feeding snails. In root-feeding snails, TTF for Ce (3.32 × 10-1) also showed a significant decrease, while TTF for DPS remained unchanged. Mixture treatments exhibited differential impacts on different snail body parts, particularly leading to biomagnification of DPS in the digestive glands and soft tissues (TTF > 1) of snails consuming roots exposed to mixtures. Both CeO2 and DPS displayed a sudden increase in assimilation efficiency following translocation to the roots. This study provides insights into changes during trophic transfer due to coexposure and plant translocation processes associated with nanoparticles, enhancing our comprehension regarding their environmental risks.

High water use efficiency due to maintenance of photosynthetic capacity in sorghum under water stress

Environmental change requires more crop production per water use to meet the rising global food demands. However, improving crop intrinsic water use efficiency (iWUE) usually comes at the expense of carbon assimilation. Sorghum is a key crop in many vulnerable agricultural systems with higher tolerance to water stress (WS) than most widely planted crops. To investigate physiological controls on iWUE and its inheritance in sorghum, we screened 89 genotypes selected based on inherited haplotypes from an elite line or five exotics lines, containing a mix of geographical origins and dry versus milder climates, which included different aquaporin (AQP) alleles. We found significant variation among key highly heritable gas exchange and hydraulic traits, with some being significantly affected by variation in haplotypes among parental lines. Plants with a higher proportion of the non-stomatal component of iWUE still maintained iWUE under WS by maintaining photosynthetic capacity, independently of reduction in leaf hydraulic conductance. Haplotypes associated with two AQPs (SbPIP1.1 and SbTIP3.2) influenced iWUE and related traits. These findings expand the range of traits that bridge the trade-off between iWUE and productivity in C4 crops, and provide possible genetic regions that can be targeted for breeding.

Tolerance to mild shading levels in cattail as related to increased photosynthesis and changes in its leaf area and anatomy

Shading is an environmental factor that has been little investigated regarding its effects on emergent aquatic plants. Typha domingensis Pers. is an emergent macrophyte that demonstrates some plasticity for self-shading, and as it can shade other species in the same area, the effect of shading on its traits deserves further investigation. The objective of the present study was to evaluate the gas exchange, leaf anatomy, and growth of T. domingensis cultivated under increasing shading intensities. The plants were collected and propagated in a greenhouse, and the clones were subjected to four shading intensities: 0% (unshaded), 35%, 73%, and 83% shading created by black nets. Growth traits, clonal production, photosynthesis, transpiration, and leaf anatomy were evaluated. The 73% and 83% shading promoted the death of all plants, but all plants survived in the 35% and unshaded treatments. Compared with the unshaded treatment, the 35% shading treatment promoted a higher photosynthetic rate and greater transpiration, supporting increased growth and production of clones. The increase in the photosynthetic rate in the 35% shading was related to the increase in leaf area which increased the photosynthesis of the whole plant. The 73% and 83% treatments inhibited the development of photosynthetic parenchyma and stomata in T. domingensis, leading to a drastic reduction in photosynthesis and energy depletion. Therefore, T. domingensis does not tolerate intense shading, but its photosynthetic characteristics and growth are favored by mild shading, a factor that may be of great importance for its competitiveness and invasive behavior.

Molecular insights into the mutualism that induces iron deficiency tolerance in sorghum inoculated with Trichoderma harzianum

Iron (Fe) deficiency is a common mineral stress in plants, including sorghum. Although the soil fungus Trichoderma harzianum has been shown to mitigate Fe deficiency in some circumstances, neither the range nor mechanism(s) of this process are well understood. In this study, high pH-induced Fe deficiency in sorghum cultivated in pots with natural field soil exhibited a significant decrease in biomass, photosynthetic rate, transpiration rate, stomatal conductance, water use efficiency, and Fe-uptake in both the root and shoot. However, the establishment of T. harzianum colonization in roots of Fe-deprived sorghum showed significant improvements in morpho-physiological traits, Fe levels, and redox status. Molecular detection of the fungal ThAOX1 (L-aminoacid oxidase) gene showed the highest colonization of T. harzianum in the root tips of Fe-deficient sorghum, a location thus targeted for further analysis. Expression studies by RNA-seq and qPCR in sorghum root tips revealed a significant upregulation of several genes associated with Fe uptake (SbTOM2), auxin synthesis (SbSAURX15), nicotianamine synthase 3 (SbNAS3), and a phytosiderophore transporter (SbYS1). Also induced was the siderophore synthesis gene (ThSIT1) in T. harzianum, a result supported by biochemical evidence for elevated siderophore and IAA (indole acetic acid) levels in roots. Given the high affinity of fungal siderophore to chelate insoluble Fe3+ ions, it is likely that elevated siderophore released by T. harzianum led to Fe(III)-siderophore complexes in the rhizosphere that were then transported into roots by the induced SbYS1 (yellow-stripe 1) transporter. In addition, the observed induction of several plant peroxidase genes and ABA (abscisic acid) under Fe deficiency after inoculation with T. harzianum may have helped induce tolerance to Fe-deficiency-induced oxidative stress and adaptive responses. This is the first mechanistic explanation for T. harzianum's role in helping alleviate Fe deficiency in sorghum and suggests that biofertilizers using T. harzianum will improve Fe availability to crops in high pH environments.

Changes in Physiological Indices, Amino Acids, and Volatile Compounds in Vitis vinifera L. cv. Pinot Noir under UV-B Radiation and Water Deficit Conditions

UV-B radiation and water deficit can challenge Pinot noir growth and fruit quality. The aim of this work is to determine the effects of UV-B and water deficit on the physiological indices, amino acids, and volatile compounds of Pinot noir vine and fruit. The results showed that both individual and combined treatments caused a decrease in the leaf SPAD, with the largest amplitude being observed in the combined treatment. Water deficit also decreased the leaf water potential and increased the juice δ13C‱ at harvest, which was the opposite of the latter under UV-B radiation. Interestingly, most of the physiological indices under combined stresses did not show significant changes compared with that under no UV-B and the well-watered control treatment. Moreover, the concentrations of amino acids and volatile compounds in the berries were determined at harvest. The amino acid contents were significantly increased by the combined treatment, particularly proline (Pro), aspartate (Arg), alanine (Ala), and threonine (Thr). There were slight increases in volatile compounds. This research substantially contributed to improve our scientific understanding of UV-B and water deficit responses in an important commercial species. In addition, it highlighted some future research to produce high-quality wines with the anticipated specific characteristics.

Morpho-Anatomical, Physiological and Biochemical Adjustments in Response to Heat and Drought Co-Stress in Winter Barley

This study aimed to investigate the combined effect of high temperatures 10 °C above the optimum and water withholding during microgametogenesis on vegetative processes and determine the response of winter barley genotypes with contrasting tolerance. For this purpose, two barley varieties were analyzed to compare the effect of heat and drought co-stress on their phenology, morpho-anatomy, physiological and biochemical responses and yield constituents. Genotypic variation was observed in response to heat and drought co-stress, which was attributed to differences in anatomy, ultrastructure and physiological and metabolic processes. The co-stress-induced reduction in relative water content, total soluble protein and carbohydrate contents, photosynthetic pigment contents and photosynthetic efficiency of the sensitive Spinner variety was significantly greater than the tolerant Lambada genotype. Based on these observations, it has been concluded that the heat-and-drought stress-tolerance of the Lambada variety is related to the lower initial chlorophyll content of the leaves, the relative resistance of photosynthetic pigments towards stress-triggered degradation, retained photosynthetic parameters and better-preserved leaf ultrastructure. Understanding the key factors underlying heat and drought co-stress tolerance in barley may enable breeders to create barley varieties with improved yield stability under a changing climate.

Influence of seasonal variation to the population growth and ecophysiology of Typha domingensis (Typhaceae)

Precipitation is an important climatic element that defines the hydrological regime, and its seasonal variation produces annual dry and wet periods in some areas. This seasonality changes wetland environments and leverages the growth dynamics of macrophytes present, including Typha domingensis Pers. This study aimed to evaluate the influence of seasonal variation on the growth, anatomy and ecophysiology of T. domingensis in a natural wetland. Biometric, anatomical and ecophysiological traits of T. domingensis were evaluated over one year at four-month intervals. Reductions in photosynthesis were evidenced at the end of the wet periods and during the dry periods, and these reductions were associated with thinner palisade parenchymas. Increased stomatal indexes and densities as well as thinner epidermis observed at the beginning dry periods can be associated with higher transpiration rates during this period. The plants maintained their water contents during the dry periods, which may be related to the storage of water in leaf trabecular parenchyma, as this is the first time that results indicate the function of this tissue as a seasonal aquiferous parenchyma. In addition, increasing proportions of aerenchymas were evident during the wet periods, which may be related to a compensation mechanism for soil waterlogging. Therefore, the growth, anatomy and ecophysiology of T. domingensis plants change throughout the year to adjust to both the dry and wet periods, providing conditions for the survival of the plants and modulating population growth.

Contrasting leaf intercellular space development in sorghum and maize modulates different tolerance capacity to water limitation

The objective of this study was to evaluate the relationship between intercellular spaces and leaf gas exchange and the effect of total intercellular space on the growth of maize and sorghum under water restriction. The experiments were conducted in a greenhouse in a 2 × 3 factorial arrangement (two plant types and three water conditions: field capacity (FC = 100%), 75%FC, and 50%FC) with 10 replicates. The lack of water was a limiting factor for maize because it showed reductions in leaf area, leaf thickness, biomass, and gas exchange parameters, while sorghum remained unchanged, maintaining its water-use efficiency. This maintenance was correlated with the growth of intercellular spaces in sorghum leaves because the increased internal volume led to better CO₂ control and prevented excessive water loss under drought stress. In addition, sorghum had more stomata than maize. These characteristics contributed to the drought tolerance of sorghum, while maize could not make the same adjustments. Therefore, changes in intercellular spaces promoted adjustments to avoid water loss and may have improved CO₂ diffusion, characteristics that are important for drought-tolerant plants.