Core Ideas Plants originated from the high‐vigor seeds presented more efficiency on nitrogen fixation. Low vigor levels resulted in higher yield variability among plants. Plants grown from high vigor seeds exhibited higher yield. Several factors may limit the germination, growth, development, and productivity of soybean [Glycine max (L.) Merrill]. Thus, seed physiological quality is important for crop establishment and uniformity. Among seed quality characteristics, vigor plays a key role for grain production. The objective of this study was to evaluate how seed vigor affects the population density, plant growth, nitrogen fixation, sugar, and starch content in nodes and these influences on yield components in soybean. Treatments consisted of varying vigor levels of seeds of the DM 5958 RSF IPRO cultivar. Using accelerated ageing test, seeds were exposed to 32°C heat for 0, 120, 192, and 216 h to obtain 90%, 75%, 63%, and 48% vigor levels. A field experiment was conducted in a randomized block design with four replicates at three locations. Root and shoot dry mass, leaf area, population density, plant height, stem diameter, nodulation, total soluble sugar and starch content, and grain yield components were measured. Plants grown from high‐vigor seeds had greater shoot and root dry mass, leaf area, population density, stem diameter, plant height, number of nodules, nodule dry mass, and thousand‐seed weight values. The numbers of productive and unproductive nodes and total soluble sugar and starch contents did not vary significantly with the treatments. Low vigor seeds resulted in increased production variability among plants while high vigor seeds resulted in higher yields due to a greater plant population density.

The use of productive cultivars with adaptability and stability and less demanding to fungicide use are critical to the sustainability of production factors. The objective of this work was to determine the per se performance of white oat cultivars and parameters of adaptability and stability on yield and grain quality in the proposition of cultivars more responsive in reducing the use fungicide. The study was conducted in Augusto Pestana, RS, Brazil, between the years 2010 and 2013. The experimental design was randomized blocks with six replicates, three with and three without fungicide. The study evaluated 14 white oat cultivars for yield and industrial capability. The white oat cultivars FAEM 4 Carlasul and URS Corona indicate high grain yield with stability and general adaptability, independent of chemical control. The cultivar URS Corona shows together high yield and thousand grain weight and hectoliter with general adaptability and stability in the absence of fungicide. Although no stability has been detected in industrial yield without the use of fungicides, cultivars of URS Charrua, URS Corona and URS Taura show high means with general adaptability.

Soybean [Glycine max (L.) Merr.] growth rate and grain yield are modified by the interception and solar radiation use efficiency. Thus, it is desirable that the most of plant photosynthetic structures intercepting solar radiation in order to have increment in carbon fixation and reflection on growth and yield. The goal of this study was to assess if soybean cultivars differ in grain yield in relation to solar radiation interception. Four soybean cultivars were evaluated at stages V6, V9, R2, R4, R6 and R8. To determine the photosynthetically active radiation interception by the canopy, the plants were divided into two parts (upper and lower strata). For grain yield components, the plants were divided into three parts (upper, middle and lower thirds). Of the photosynthetically active radiation intercepted by the vegetative canopy at the reproductive stages, the maximum observed intercept was 5.2% in the lower stratum of the plants. The number of infertile nodes increased in the lower third of plants due to low interception of solar radiation in this plant region. Thus, the soybean cultivars more efficient in intercepting photosynthetically active radiation inside the vegetative canopy showed higher grain yields.

Environmental conditions affect crop yield, and water deficit has been highlighted by the negative impact on soybean grain production. Radicial growth in greater volume and depth can be an alternative to minimize losses caused by a lack of water. Therefore, knowledge of how soybean roots behave before the chemical, physical, and biological attributes of the soil can help establish managements that benefit in-depth root growth. The objective was to evaluate the growth of soybean roots in response to chemical, physical, and biological variations in the soil, in different soil locations and depths. Six experiments were conducted in different locations. Soil samples were collected every 5 cm of soil up to 60 cm of soil depth for chemical, physical, and biological analysis. The roots were collected every 5 cm deep up to 45 cm deep from the ground. The six sites presented unsatisfactory values of pH and organic matter, and presented phosphorus, potassium, and calcium at high concentrations in the first centimeters of soil depth. The total porosity of the soil was above 0.50 m3 m−3, but the proportion of the volume of macropores, micropores, and cryptopores resulted in soils with resistance to penetration to the roots. Microbial biomass was higher on the soil surface when compared to deeper soil layers, however, the metabolic quotient was higher in soil depth, showing that microorganisms in depth have low ability to incorporate carbon into microbial biomass. Root growth occurred in a greater proportion in the first centimeters of soil-depth, possibly because the soil attributes that favor the root growth is concentrated on the soil surface.

Drought stress is one of the most severe environmental constraints on plant production. Under environmental pressures, complex daily heliotropic adjustments of leaflet angles in soybean can help to reduce transpiration losses by diminishing light interception (paraheliotropism), increase diurnal carbon gain in sparse canopies and reduce carbon gain in dense canopies by solar tracking (diaheliotropism). The plant materials studied were cultivar BR 16 and its genetically engineered isoline P58, ectopically overexpressing AtDREB1A, which is involved in abiotic stress responses. We aimed to follow the movements of central and lateral leaflets in vegetative stages V7-V10 and reproductive stages R4-R5, integrating the reversible morphogenetic changes into an estimate of daily plant photosynthesis using three-dimensional modeling, and to analyze the production parameters of BR 16 and P58. The patterns of daily movements of central leaflets of BR 16 in V7-V10 and R4-R5 were similar, expressing fewer diaheliotropic movements under drought stress than under non-limiting water conditions. Daily heliotropic patterns of lateral leaflets in V7-V10 and R4-R5 showed more diaheliotropic movements in drought-stressed P58 plants than in those grown under non-limiting water conditions. Leaf area in R4-R5 was generally higher in P58 than in BR 16. Drought significantly affected gas exchange and vegetative and reproductive architectural features. DREB1A could be involved in various responses to drought stress. Compared with the parental BR 16, P58 copes with drought through better compensation between diaheliotropic and paraheliotropic movements, finer tuning of water-use efficiency, a lower transpiration rate, higher leaf area and higher pod abortion to accomplish the maximum possible grain production under continued drought conditions.

Leaf angle and plant architecture may determine the penetration of phytosanitary products in the low layer of soybean [Glycine max (L.) Merr.] plants, make the diseases control difficult, and promote losses in crop productivity. Strategies should be studied to increase the efficiency of deposition of phytosanitary products inside the canopy. The hypothesis of this work was that reversible leaf movements and plant architecture may change the penetration of spray droplets into the low layer of soybean plants. We evaluated whether plant architectural characteristics affect spray droplet deposition and monitored if heliotropic movements can increase the efficiency of applications of plant protection products. Four soybean cultivars were investigated. Plant architectural characteristics were evaluated in the V6, V9, R2, and R4 phenological stages, interception of photosynthetically active radiation was evaluated in the V9, R2, and R4 stages, and heliotropic movements were evaluated in the V6 and R4 stages. Sprayings were performed at 0800, 1100, 1400, and 1700 h in the R4 stage. Occurrence of diaheliotropic movements was greater in the V6 than in the R4 stage. The number of branches per plant in the R4 stage was 8, 14, 6, and 14, the branch size was 10.6, 25.8, 12.5, and 21.4 cm, and the leaf area index was 4.2, 4.7, 3.7, and 4.7 for cultivars ‘BMX Ativa RR’, ‘NA 5909 RG’, ‘95R51’, and ‘BMX Potência RR’, respectively. Those architectural characteristics played the most important role in droplet penetration into the low canopy layer. Droplet deposition in the low canopy layer was greater at daylight hours close to noon, showing that the paraheliotropism occurring in those daily hours is more helpful to droplet penetration deeper into the canopy than in other hours.

The aim was to evaluate the interactive effects on biochemistry and physiology of soybean plants exposed to simultaneous xenobiotic and water deficit stresses, and the possible attenuation of plant damage by an antioxidant agent. Soybean plants were submitted to eight different soil water potentials, in two experiments (first experiment: −0.96, −0.38, −0.07, −0.02 MPa, and second experiment: −3.09, −1.38, −0.69, −0.14 MPa), xenobiotic, and antioxidant agent applications. Was observed a reduction in water status, gas exchange, photosynthetic pigments, photosystem II quantum yield, and increased leaf temperature in plants under low water availability. Water deficit also induced oxidative stress by the increased production of reactive oxygen species, cellular and molecular damage, and induction of the antioxidant defense metabolism, reduction of gas exchange, water status, and photosynthetic efficiency. The xenobiotic application also caused changes, with deleterious effects more pronounced in low soil water availability, mainly the reactive oxygen species production, consequently the antioxidant activity, and the oxidative damages. This indicates different responses to the combination of stresses. Antioxidant enzyme activity was reduced by the application of the antioxidant agent. Principal Component Analysis showed a relation with the antioxidant agent and reactive oxygen species, which is probably due to signaling function, and with defense antioxidant system, mainly glutathione, represented by thiols.

The soybean plant architecture in relation to better solar radiation interception and production gain is an aspect that requires a better understanding, since soybean is an important crop worldwide. The genetic traits, management and environmental conditions are points that further extend the range of issues on crop productivity. The light quality is measured by the red/far-red (R/FR) ratio (R ∼ 660 nm, FR ∼ 730 nm). This affects the plant growth and morphological developments in different ways. The plant leaves change their angle during the day to better intercept radiation. This heliotropic movement and some computational models together have been used to enhance some agricultural practices. Soybean plant is dependent on the interaction between genotype and environment. Thus, the enhanced understanding in relation to photosynthetic activity, grain yield by light interception efficiency and culture protection managements in soybean are covered.