Silvana de Paula Quintão Scalon

Sugarcane cultivation in Brazil is a major agricultural industry, generating employment and playing a vital role in the production of sugar and ethanol. To maintain high productivity, appropriate management and cultural practices are essential, particularly during the sprouting phase, which is vulnerable to water stress. This study aimed to mitigate the effects of water stress during the sugarcane transplanting through the inoculation of plant growth-promoting rhizobacteria (PGPR) at planting. The responses of photosynthetic metabolism and defense mechanisms, as well as plant growth, were evaluated in two sugarcane varieties RB966928 and CTC7515BT exposed to the following conditions: control (70% of soil water retention capacity, WRC), water deficit (WD): 40% WRC, WD + Bacillus subtilis , and WD + Mix ( B. subtilis , B. pumilus , and B. amyloliquefaciens ). Results showed that drought stress significantly reduced developmental potential and biomass accumulation, as well as negatively affected water content and gas exchange parameters, including photosynthesis, transpiration, stomatal conductance, and intercellular CO₂ concentration. However, the inoculation of PGPR enhanced the enzymatic activity of peroxidase and superoxide dismutase in both cultivars, alleviating the negative effect of water deficit. Therefore, PGPR inoculation represents a promising strategy to alleviate water stress, promote antioxidant enzyme activity, and enhance crop resilience, ultimately contributing to sustainable sugarcane production.

Drought-induced stress promotes the overproduction of reactive oxygen species, which impair the morphophysiology of plants of socioeconomic interest, such as wheat. Thus, studies are needed to establish agents with stress alleviating potential, and in this scenario, bioinputs show promise. We aimed to evaluate the potential of bioinputs to alleviate oxidative stress and contribute to wheat physiology during and after exposure to drought stress. The seeds were inoculated with the following bioinputs: i) microalgae Parachlorella sp., ii) Bacillus subtilis , iii) Trichoderma harzianum , iv) Parachlorella sp. + B. subtilis , v) Parachlorella sp. + T. harzianum , and vi) Parachlorella sp. + B. subtilis + T. harzianum , in addition to the control (without bioinputs), associated with two water regimes: a) irrigated = daily irrigation and b) water deficit: suspension of irrigation, with assessments in stress and post-stress phase. Plants under water deficit inoculated with Parachlorella sp. and Bacillus subtilis , either isolated or associated, reduced malondialdehyde and hydrogen peroxide contents, suggesting physiological and biochemical memory induced by bioinputs, alleviating oxidative damage and increasing the efficiency of the defense system through the activation of superoxide dismutase and peroxidase, which contributed to maintaining the photosynthesis and stomatal conductance. In post-stress phase, the bioinputs contributed in plants with a more efficient resumption of gas exchange. Inoculation with isolated T. harzianum did not mitigate oxidative and physiological stress. Seed inoculation of bioinputs is a promising practice in inducing physiological tolerance and resilience by phenotypic plasticity of wheat to water deficit.

Biological nitrogen fixation is a promising strategy to reduce reliance on synthetic nitrogen fertilizers. This study evaluated foliar inoculation with Methylobacterium symbioticum (Blue N™) and Azospirillum brasilense (Masterfix Gramineas™), alone or combined, in wheat (Triticum aestivum L. cv. TBIO Calibre) under Cerrado abiotic stresses and nitrogen (N) volatilization losses. Field trial (2024 season) with five treatments over basal NPK 15.15.15: T1(no urea aplication); T2 (+ 72 kg ha⁻¹ N-urea+NBPT); T3(+ 250 mL ha⁻¹ Masterfix Gramineas™); T4 (+ 333 g ha⁻¹ Blue N™); T5(+ 250 mL ha⁻¹ Masterfix Gramineas™ + 333 g ha⁻¹ Blue N™) at V3 stage. Co-inoculation (T5) increased foliar N (6.6%), phosphorus (P) (7.5%), potassium (K) (12.8%), zinc (Zn) (12.5%), manganese (Mn) (3.1%) and boron (B) (11.1%) versus T1; A. brasilense alone (T3) increased K (10.4%), Zn (5.5%) and B (122.2%), representing the greatest boron accumulation among all treatments; urea+NBPT (T2) only excelled in chlorophyll b (15.9%). Peroxidase activity was reduced Urea+NBPT (T2) (87.7%), A. brasilense alone (T3) (79.7%), M. symbioticum alone (T4) (46.8%) and co-inoculation (T5) (93%) compared to T1. Foliar co-inoculation of A. brasilense + M. symbioticum optimizes nutrient uptake, strengthens antioxidant defenses and enhances the physiological response capacity of wheat under field conditions, offering a sustainable alternative to synthetic nitrogen in wheat grown in the Brazilian Cerrado.

Phosphorus (P) availability is currently a limiting factor for agricultural production, especially in tropical soils, and its interaction with cationic micronutrients can significantly affect physiological efficiency and nutrient uptake by plants. Therefore, this study aimed to evaluate the uptake kinetic parameters described by the Michaelis–Menten model (Vmax, Km, and Cmin) for P as a function of the supply of Cu, Fe, Mn, and Zn, as well as the kinetic parameters of Cu, Fe, Mn, and Zn as a function of P supply in cotton (Gossypium hirsutum L.). The experiment was conducted in a greenhouse at the experimental unit of CENA, in Piracicaba, São Paulo, Brazil, using individual pots. Phosphorus concentration and accumulation were reduced only under Fe and Zn deficiency, with reductions of up to 60% in the shoots and 85% in the roots. Zn deficiency caused a drastic reduction in P uptake capacity, with Vmax decreasing from 590 to 50.85 µmol g⁻¹ h⁻¹ (approximately a 12-fold reduction), accompanied by an increase in Cmin (from 269 to 1508 µmol L⁻¹). In terms of micronutrient kinetics, P omission reduced plant growth and affected only Fe and Zn uptake. For Fe, Km increased from 12.82 to 27.31 µmol L⁻¹ and Cmin from 1.03 to 20.51 µmol L⁻¹. For Zn, and Vmax decreased from 0.16 to 0.02 µmol g⁻¹ h⁻¹ (approximately 8-fold), while Cmin increased from 0.08 to 1.56 µmol L⁻¹. These results demonstrate a strong interaction between P, Fe, and Zn, highlighting their regulatory roles in nutrient uptake and providing mechanistic insights into plant nutritional efficiency.

Flooding, depending on exposure time, can be stressful and impair plant morphophysiology, but the foliar application of salicylic acid (SA) is an efficient physiological management to alleviate these negative effects. We aimed to evaluate the responsiveness of Hymenaea courbaril L. to flooding and the potential of SA to alleviate the associated stress. Seedlings received foliar applications of four SA concentrations (0, 100, 200, and 400 mg L-1), were exposed to two water regimes (control and flooded), and were evaluated at 15 and 30 days. The treatments were arranged in a subplot scheme, with water regimes assigned to plots and SA doses to subplots. The evaluation periods were treated as time-structured plots. Although flooding decreased photochemical activity in photosystem II, especially at 15 days, it did not negatively affect seedling growth. Foliar application of SA at varying doses increased chlorophyll indices and stimulated seedling growth, as reflected in biomass production, but did not affect photochemical efficiency. H. courbaril seedlings are physiologically responsive to flooding, but this did not reflect in growth through adjustment mechanisms. Foliar application of SA at a dose between 242-266 mg L-1 stimulates the growth of H. courbaril seedlings, regardless of exposure time and water regimes.

Glufosinate is often used for pre-harvest desiccation in soybeans, however, its use is not feasible in varieties with tolerance to this herbicide. Thus, the objective of this study was to evaluate the performance of the herbicides amicarbazone, saflufenacil, flumioxazin, diquat, carfentrazone, tiafenacil and florpyrauxifen, applied alone or in combination, for the pre-harvest desiccation of glufosinate tolerant soybean. To this end, a field experiment was conducted in a randomized block design with four replications. Treatments were applied at the R7.3 phenological stage, with evaluations for defoliation, desiccation, grain moisture, membrane damage, fluorescence, and antioxidant enzymes. For defoliation, except for saflufenacil and the untreated control, all the treatments presented values greater than 80% at 10 days after application (DAA). Membrane damage exceeded 60% for protoporphyrinogen oxidase (PROTOX) inhibitors, whereas for florpyrauxifen, it was less than 10%. The application of amicarbazone resulted in an electron transport rate (ETR) of 1.5. In terms of protein expression, the highest levels (22 mg/g FW) were observed for the combination of amicarbazone with florpyrauxifen and diquat. For the antioxidant enzymes peroxidase and superoxide dismutase, the highest expression was observed for florpyrauxifen + saflufenacil, with values of approximately 2.7 × 10-5 mg/g FW, this suggested that products characterized by a delayed expression of phytotoxicity and minimal membrane damage lead to decreased activity of antioxidant enzymes. Thus, in the pre-harvest desiccation of glufosinate-ammonium-tolerant soybean, considering both productive and physiological aspects, diquat, applied alone or in association with other herbicides, stands out as the most promising management alternative

Water deficit is a stressful condition that negatively affects photosynthetic metabolism and plant growth. In an attempt to alleviate the effect of low water availability, the use of water-retaining polymer (hydrogel) has proven to be a viable strategy. We aimed to evaluate the effect of the hydrogel on photosynthetic metabolism and antioxidant protection in Dipteryx alata Vogel. seedlings under water deficit and on potential recovery in post-stress. The seedlings grown under the following water regimes: i) control – irrigated daily, ii) water deficit – suspension of irrigation, and iii) water deficit + hydrogel – addition of polymer in the time of transplanting. Assessments were carried out at photosynthesis close to zero and at recovery (resumption of irrigation after). We observed decreased in gas exchange and growth of seedlings subjected to water deficit in photosynthesis close to zero, but those with hydrogel maintained high values, in addition to a more efficient recovery. Although the hydrogel did not contribute to chlorophyll a fluorescence, it favored enzymatic regulation similar to control plants, especially peroxidase in leaves and roots, and superoxide dismutase in roots. D. alata responds to water deficit activating protective mechanisms through physiological and antioxidants adjustments that ensure its survival when exposed to water deficit and its recovery post-stress, indicating phenotypic plasticity. The hydrogel contributes positively to the photosynthetic, enzymatic, and quality maintenance of D. alata seedlings during and after stress.

The timing of ammonium glufosinate application influences its efficacy in the preharvest desiccation of soybean. The objective of this study was to evaluate the performance of two glufosinate‐ammonium formulations applied at different times of the day for the preharvest desiccation of soybeans and to assess their physiological impacts on the crop. Two experiments were conducted, one for each formulation (Finale and Trunfo), in a randomized complete block design with four replications. The treatments consisted of applications at the following times: 6:20 a.m., 10:20 a.m., 2:20 p.m., 6:20 p.m., 10:20 p.m. and 2:20 a.m. The following parameters were assessed: defoliation, desiccation, quantification of green pixels, membrane damage, initial fluorescence ( F ₀ ), electron transport rate (ETR), ammonia (NH ₃ ) accumulation, activity of antioxidant enzymes (peroxidase and superoxide dismutase), daily grain moisture, yield, and thousand‐grain weight. For Finale, the highest defoliation rates (90%) were achieved with applications at 6:20 a.m. and 10:20 a.m., whereas for Trunfo, the highest rates (85%) were achieved at 6:20 a.m., 10:20 a.m. and 2:20 p.m. The greatest reduction in green pixels occurred with applications at 6:20 a.m. and 10:20 a.m., resulting in 95% and 100% decreases in green area, respectively. For both formulations, the greatest membrane damage (60 µs/cm) was observed with the 10:20 a.m. application. The ETR reached 25 and 55 μmol for Finale and Trunfo, respectively. Significant antioxidant enzyme activity was observed for the 6:20 a.m. and 10:20 a.m. treatments, while the highest ammonia (NH ₃ ) accumulation occurred at 6:20 p.m. Finale exhibited greater efficacy under high‐light conditions. The Trunfo performed better under low‐light conditions.

Co-inoculation of plant growth-promoting bacteria and the application of hormones can be practical for soybeans. We aimed to evaluate the effect of co-inoculation methods of Azospirillum brasilense + Pseudomonas fluorescens and auxin application on the nutrition and morphophysiology of soybeans. The co-inoculation methods were: control; inoculation with Bradyrhizobium spp. only; and co-inoculation with Bradyrhizobium spp. and a commercial source containing A. brasilense + P. fluorescens applied via seed, via foliar at stage V3, or via seed + foliar, associated or not with the application of auxin at stage V4. The application of auxin had little influence on photochemical yield. The best values of photochemical activity in the reaction centers of photosystem II occurred in plants co-inoculated via seed + foliar. Photosynthesis was higher in plants co-inoculated via seed and via seed + foliar, as were intrinsic carboxylation and water use efficiency. The highest nitrogen contents were observed in the control treatment and in the seed + foliar co-inoculation, regardless of auxin application. The control plants showed higher potassium, magnesium, and sulfur contents, while auxin application increased calcium content in plants. The application of auxin contributed to an increase in leaf area and biomass of leaves, roots, and nodules. Co-inoculation via foliar and seed + foliar routes anticipated flowering and increased the number of pods per plant. Co-inoculation of A. brasilense + P. fluorescens via seed + foliar routes promoted improvements in soybean morphophysiology, while auxin application contributed positively to soybean morphophysiology and nutrition.