Rice (Oryza sativa L.) plays a pivotal role in the Brazilian economy, serving as a staple food for more than half of the world’s population and thereby contributing to global food security. Projections of future climate change scenarios indicate an increase in extreme weather events. Among climate variables that impact the development and productivity of irrigated rice, solar radiation is one of the most important in defining productive potential. Understanding the risks imposed on agricultural production by the occurrence of days with reduced luminosity availability is crucial for guiding adequate responses that mitigate the negative impacts of climate variability. Therefore, this study aimed to investigate the effect of shade on the metabolism and productivity of irrigated rice plants, with a specific focus on the synthesis of photosynthetic pigments, carbohydrate accumulation, invertase activity, and the nutritional status and grain yield of rice. For this, the study was conducted on the field rice cultivars IRGA 424 RI, BRS PAMPA, and BRS PAMPEIRA, which were subjected to 35% shading using black nylon netting installed when the plants reached the reproductive stage (R0). The restriction was maintained until the R4 stage, and later, from the R4 stage until the R9 stage. After the imposition of treatments, evaluations took place at the phenological stages R2, R4, R6, and R8. In shaded plants, a higher content of photosynthetic pigments and a lower accumulation of carbohydrates were observed, which was reflected in an increase in the activity of invertase enzymes. These conditions were able to potentiate effects on the nutritional status of the plants, in addition to reducing productivity and 1000-grain weight and increasing spikelet sterility, due to changes in the source–sink relationship, with effects more pronounced in cultivars BRS PAMPA and BRS PAMPEIRA during the R4–R9 period.

Bioactive compounds in plants, such as carrots, have been widely used for their benefits. In agriculture, their potential as biostimulants still needs to be investigated, especially for their possible antioxidant action in plants subjected to abiotic stresses, such as salinity. This work aimed to evaluate the elicitor potential of carrot extract in alleviating salt stress in rice plants. This study aimed to evaluate the elicitor potential of carrot extract in alleviating saline stress in the rice cultivars BRS Querência and BRS 358. Aqueous extracts of carrot roots at concentrations of 0% (water), 25%, 50%, and 100% were used to soak rice seeds for 48 h, which were then subjected to different concentrations of NaCl (0, 25, 75, and 150 mM). To determine the effect of carrot extract as an elicitor under saline stress conditions, the following tests were conducted: germination, seedling length, dry mass, and oxidative stress through the activity of antioxidant enzymes, superoxide dismutase (SOD), ascorbate peroxidase (APX), catalase (CAT), peroxide content, and lipid peroxidation (hydrogen peroxide H₂O₂ and malonaldehyde MDA). Carrot extract increased the germination rate and maintained germination even under increased salinity rates in both cultivars. The application of 25 mM NaCl also boosted germination rates, followed by a significant decrease due to increased salinity rates. Shoot and root lengths and dry mass parameters showed a linear decrease in response to increasing NaCl concentrations. The activities of superoxide dismutase (SOD), ascorbate peroxidase (APx), and catalase (CAT) enzymes tended to decrease as the concentration of carrot extract increased, whereas the opposite was observed with NaCl application. Based on the combined analysis of the evaluated parameters, carrot extract application under the tested conditions was efficient in mitigating oxidative stress caused by high salinity conditions.

The present work aimed to investigate the effect of increasing CO₂ concentration on the growth, productivity, grain quality, and biochemical changes in quinoa and amaranth plants. An experiment was conducted in open chambers (OTCs) to evaluate the responses of these species to different levels of CO₂ {a[CO₂] = 400 ± 50 μmol mol⁻¹ CO₂ for ambient CO₂ concentration, e[CO₂] = 700 ± 50 μmol mol⁻¹ CO₂ for the elevated CO₂ concentration}. Growth parameters and photosynthetic pigments reflected changes in gas exchange, saccharolytic enzymes, and carbohydrate metabolism when plants were grown under e[CO₂]. Furthermore, both species maintained most of the parameters related to gas exchange, demonstrating that the antioxidant system was efficient in supporting the primary metabolism of plants under e[CO₂] conditions. Both species were taller and had longer roots and a greater dry weight of roots and shoots when under e[CO₂]. On the other hand, the panicle was shorter under the same situation, indicating that the plants invested energy, nutrients, and all mechanisms in their growth to mitigate stress in expense of yield. This led to a reduction on panicle size and, ultimately, reducing quinoa grain yield. Although e[CO₂] altered the plant’s metabolic parameters for amaranth, the plants managed to maintain their development without affecting grain yield. Protein levels in grains were reduced in both species under e[CO₂] in the average of two harvests. Therefore, for amaranth, the increase in CO₂ mainly contributes to lowering the protein content of the grains. As for quinoa, its yield performance is also affected, in addition to its protein content. These findings provide new insights into how plants C3 (amaranth) and C4 (quinoa) respond to e[CO₂], significantly increasing photosynthesis and its growth but ultimately reducing yield for quinoa and protein content in both species. This result ultimately underscore the critical need to breed plants that can adapt to e[CO₂] as means to mitigate its negative effects and to ensure sustainable and nutritious crop production in future environmental conditions.

The quality of soybean seeds is essential for the success of the crop, with the seed coat being a vital element in protecting the embryo. The objective of this study was to understand the chemical causes and dynamics of the formation of cracks in soybean seed coat. The seed coats of five lots, with and without cracks, were used, and chemical analyses were conducted to evaluate the contents of silicon, nitrogen, phosphorus, potassium, calcium, and magnesium. Anatomical analysis was also performed; for this, the seed coats were cut and observed under a microscope to identify the cell layers and the presence of cracks. The results showed that seeds with cracks had higher phosphorus and magnesium contents and lower calcium content. Seed coat thickness ranged from 47 to 230 micrometers, and the cracks occurred preferentially in the thicker regions. The crack initiates between the palisade cells and can extend, creating air pockets that accumulate water and chemicals. Thus, cracks in soybean seed coat are related to the contents of phosphorus, calcium, and magnesium, and variations in seed coat thickness contribute to their occurrence. Cracks affect permeability and can reduce the quality of the seeds.

Soil salinization is a major constraint on irrigated rice cultivation, mainly due to poor irrigation management and cropping in coastal areas. Seed priming is widely recognized as a cost-effective and practical approach to enhance early growth and improve tolerance to abiotic stresses, including salinity. This study evaluated the effects of seed priming of rice seeds from two cultivars, BRS Querência (Indica) and BRS 358 (Japonica), using aqueous carrot root extract at 0% (water), 25%, and 50% concentrations for 48 h. Seeds were sown in rhizotrons and exposed to 0, 75, or 150 mM NaCl. Morphological, physiological, and biochemical traits were evaluated at 21 days after sowing. Seed priming with carrot extract was associated with improved growth and physiological responses under salinity stress. Under 150 mM NaCl, primed seedlings showed approximately 40% higher chlorophyll index, 35% greater root volume, and 30% higher shoot dry mass compared to unprimed controls. The 25% extract concentration was particularly effective for BRS Querência, which showed enhanced root elongation and a higher nitrogen balance index. Activities of superoxide dismutase, ascorbate peroxidase, and catalase increased by 45–70%, while hydrogen peroxide and malondialdehyde levels decreased by approximately 50%, suggesting enhanced antioxidant responses and improved redox balance. Anthocyanin accumulation also increased in specific cultivar–treatment combinations, suggesting a potential effect on secondary metabolism and antioxidant pathways. Overall, carrot-based seed priming was associated with improved seedling performance, pigment stability, and regulation of oxidative stress under saline conditions. These results suggest that carrot-based seed priming may improve physiological performance under salinity stress.