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Temperature is the primary factor affecting the morpho-physiological, developmental, and yield attributes of soybean. Despite several temperature and soybean studies, functional relationships between temperature and soybean physiology and yield components are limited. An experiment was conducted to determine the optimum temperature for soybean gas exchange and yield components using indeterminate (Asgrow AG5332, AG) and determinate (Progeny P5333 RY, PR) growth habit cultivars. Plants grown outdoors were exposed to 5 day/night temperature treatments, 21/13, 25/17, 29/21, 33/25, and 37°C/29°C, from flowering to maturity using the sunlit plant growth chambers. Significant temperature and cultivar differences were recorded among all measured parameters. Gas exchange parameters declined with increasing temperature treatments during the mid-pod filling stage, and quadratic functions best described the response. The optimum temperature for soybean pod weight, number, and seed number was higher for AG than PR, indicating greater high-temperature tolerance. Soybean exposed to warmer parental temperature (37°C/29°C) during pod filling decreased significantly the transgenerational seed germination when incubated at 18, 28, and 38°C. Our findings suggest that the impact of temperature during soybean development is transferable. The warmer temperature has adverse transgenerational effects on seed germination ability. Thus, developing soybean genotypes tolerant to high temperatures will help growers to produce high-yielding and quality beans. The quantified temperature, soybean physiology, and yield components-dependent functional algorithms would be helpful to develop adaptation strategies to offset the impacts of extreme temperature events associated with future climate change.

Soybean seed quality is often determined by its constituents which are important to sustain overall nutritional aspects. The objective of this study was to investigate the effects of soil moisture stress during reproductive stage on seed quality and composition. Plants were subjected to five levels of soil moisture stresses at flowering, and yield and quality traits were examined at maturity. Seed protein, palmitic and linoleic acids, sucrose, raffinose, stachyose, N, P, K, and Ca significantly decreased whereas oil, stearic, oleic and linolenic acids, Fe, Mg, Zn, Cu, and B increased in response to soil moisture deficiency. The relationship between seed protein and oil was negatively correlated. The changes in seed constituents could be due to changes in nutrient accumulation and partitioning in soybean seeds under water stress. This information suggests the requirement of adequate soil moisture during flowering and seed formation stages to obtain the higher nutritional value of soybean seeds.

Ambient temperature has a profound effect on agricultural production. Generally, sub- and supra-optimal temperatures have a negative effect on growth/yield, provided the deviation for optimal is large enough. On average, mean global temperatures are projected to increase by 0.3 to 0.6 °C per decade over the next century. Nighttime temperatures (TN) are projected to increase faster (20%–40% by 2100) than day maximum temperatures (TD). Therefore, an experiment was conducted to determine the effects of projected sub- and supra-optimal day/night temperatures on two diverse rice (Oryza sativa) cultivars, IR6 and Rex, during reproductive growth. At flowering, nine different day/night temperature treatments (TTs) were imposed and maintained until harvesting using sunlit growth chambers (SPAR units). Alterations to plant metabolism were evaluated using CO2 response functions, also, to survey gas exchange readings under ambient conditions. Net photosynthesis (AN) declined under both TD and TN effects. The decline in maximum carboxylation rate allowed by Rubisco (Vcmax) and maximal rate of electron transport allowed by the thylakoid reactions (Jmax), with increasing TN mainly contributed to the decline in AN. Dark respiration rates (RD) declined with increasing temperatures could be a cultivars acclimation mechanism to prevent excessive carbon losses. Cultivars varied mainly for primary photochemistry, with cultivar Rex exhibited significantly higher RD, and pigment contents but lower Jmax than IR6 across TTs. The information on genetic, biochemical and physiological processes in these two diverse cultivars under varied temperature regimes could be useful for developing breeding tools to enhance thermotolerance in US rice cultivars for future climatic conditions.

Developing a model for soybean seed emergence offers a tool producers could use for planting date options and in predicting seedling emergence. In this study, temperature effects on soybean seed emergence were quantified, modeled, and validated. The data for seed emergence model development was generated at varying temperatures, 20°C/12°C, 25°C/17°C, 30°C/22°C, 35°C/27°C, and 40°C/32°C, on two soybean cultivars, Asgrow AG5332 and Progeny P 5333 RY. Time for 50% emergence (t50%) was recorded, and seed emergence rate (SER) was estimated as reciprocal to time at each temperature in both the cultivars. No differences were observed between the cultivars in their response to temperature. A quadratic model (QM) best described the relationship between t50% and SGR and temperature (R2 = 0.93). Two sets of experiments were conducted to validate the model. In Experiment 1, 17 time-series planting date studies with the same cultivars were used by utilizing diurnal and seasonal changes in temperature conditions. In the second experiment, sunlit growth chambers with 3 different day/night temperatures, low—20°C/12°C, optimum—30°C/22°C, and high—40°C/32°C, and 64 soybean cultivars belonging MG III, IV, and V, were used. Air temperature and t50 were recorded, and SGR was estimated in all experiments. No differences were recorded among the cultivars for t50% and SGR, but differences were observed among seeding date and temperature experiments. We tested QM and traditionally used Growing Degree Days models against the data collected in validation experiments. Both the model simulations predictions agreed closely with the observed data. Based on model statistics, R2, root mean square errors (RMSE), and comparison of observations and predictions to assess model performance, the QM model performed better than the GDD model for soybean seed emergence under a wide range of cultivars and environmental conditions.

Temperature is considered as a major environmental factor upon which the storage behavior of sweetpotatoes depends. To quantify shoot and root vigor responses during sweetpotato early transplant establishment, an experiment was conducted using sunlit environmental growth chambers at three day/night temperatures, 22/14 (low), 30/22 (optimum), 38/30 °C (high). Ten sweetpotato cultivars were transplanted in pots for 20 days and several shoot and root morphological and physiological traits were assessed. Sweetpotato cultivars varied significantly for many traits measured particularly root components. High and low temperatures significantly decreased the production of storage root number. Low temperature caused a marked decrease in vine length, node number, leaf area, total biomass, and net photosynthesis causing 95, 70, 78, 66, and 36% reduction compared to the optimum temperature. At high temperature, average leaf area was seven times more than optimum indicating strong temperature effects on leaf number, size, and leaf area development. Principal component analysis was used to classify sweetpotato cultivars to low and high-temperature tolerant, intermediate, and sensitive groups. The sweetpotato cultivars O’henry and Bonita were identified as tolerant, Evangeline, B14, Vardaman, and Covington as intermediate tolerant, and NC05198 and Travis as sensitive to both low and high temperatures. A poor correlation was observed between low and high temperature response indices indicating that cold and heat tolerance mechanisms are different and the selection has to be made independently in developing tolerance to low and high temperatures. The identified low and high temperature tolerant cultivars and their associated morpho-physiological characteristics may be useful for breeders to develop new cultivars that could withstand variable temperatures projected to occur in future climates aiming to increase storage root yield.

Soil moisture stress is the major abiotic stress factor that causes extensive losses to soybean production worldwide. Quantitative relationships between soil moisture deficit and yield components are needed to improve algorithms of the existing soybean models predictability. The objective of this study was to quantify water stress effects on various plant growth and reproductive traits using two soybean cultivars with distinct growth habits, indeterminate type, Asgrow AG5332 and determinate type, Progeny P5333RY. Plants grown in pots outdoors were moved into sunlit controlled environment at flowering stage. Five water stress treatments, 100, 80, 60, 40, and 20% of daily evapotranspiration of the control, were imposed at flowering and continued until maturity. Plant height and node numbers were recorded at 7-day intervals. Plant component dry weights, pod distribution patterns, and pod and seed yield were measured at the final harvest. A quadratic function best described the relationship between soil moisture content and midday leaf water potential and − 1.0 MPa leaf water potential was achieved at optimum soil moisture content of 0.15 m3 m− 3 soil. The middle region of the canopy in both cultivars accounted for about 60% of final yield compared to top and bottom regions. Branch pod yield was about threefold as high as mainstem yield, and it was more sensitive to moisture stress than mainstem yield. Harvest index declined linearly with decreasing soil moisture levels in the cultivars, and rate of decline in Asgrow AG5332 was lower (slope = 1.68) than the decline of Progeny P5333RY (slope = 2.42) m3 m− 3. The functional relationships between soil moisture stress and yield components will be useful to aid farm managers in scheduling irrigation and to improve the functionality of soybean crop models under varying soil moisture conditions.

This study was conducted to determine if root, shoot, and gas exchange traits of determinate and indeterminate soybean cultivars respond differently to soil water deficit. The effect of soil water deficit imposed 4 and 10 days after sowing on growth and development parameters of determinate and indeterminate soybeans was evaluated for 18 and 30 days in experiment I and II, respectively. At both 18 and 30 days after seeding, nearly all root, shoot, and physiological parameters were inversely correlated with the soil moisture level, and the adverse effects of drought stress were more evident in Progeny P5333RY than in Asgrow AG5332. For both cultivars, the effect of soil water deficit on net photosynthesis was mainly due to stomatal limitations. The developed algorithms for the plant processes based on the environmental productivity index were not different between the cultivars, suggesting that soybean plants respond in a similar way irrespective of their growth habits, probably due to the shorter period of water stress.

Effects of environmental stressors on the parent may be transmitted to the F1 generation of plants that support global food, oil, and energy production for humans and animals. This study was conducted to determine if the effects of drought stress on parental soybean plants are transmitted to the F1 generation. The germination and seedling vigor of F1 soybean whose maternal parents, Asgrow AG5332 and Progeny P5333RY, were exposed to soil moisture stress, that is, 100, 80, 60, 40, and 20% replacement of evapotranspiration (ET) during reproductive growth, were evaluated under controlled conditions. Pooled over cultivars, effects of soil moisture stress on the parents caused a reduction in the seed germination rate, maximum seed germination, and overall seedling performance in the F1 generation. The effect of soil moisture stress on the parent induced an irreversible change in the seed quality in the F1 generation and the effects on seed quality in the F1 generation were exasperated when exposed to increasing levels of drought stress. Results indicate that seed weight and storage reserve are key factors influencing germination traits and seedling growth. Our data confirm that the effects of drought stress on soybean are transferable, causing reduced germination, seedling vigor, and seed quality in the F1 generation.

OBJECTIVES: The objectives of this study were to investigate the impact of flooding on: Reproductive, growth, and development Nutrient concentration Soybean productivity and resilient in changing environment METHODS: An out-door pot-culture experiment was conducted to determine flooding effects on soybean growth and physiology during the reproductive period. Cultivar Asgrow AG5332 was seeded in 5.2 L pots filled with 3:1 by volume fine sand and topsoil and irrigated with full-strength Hoagland's nutrient solution. After 34 days of sowing, treatments were induced flooding at 2.5 cm above the soil surface for 16 additional days. Measurements were made on soil oxygen content and leaf gas exchange and pigment. Growth parameters and plant components biomass were also measured, 66 days after sowing. RESULTS: Soil oxygen levels declined rapidly to 0% in around 5-days of flood treatment, but the control remained 18%. The nutrient: N and Mg concentrations significantly decreased with flooding. All plant growth parameters and reproductive potential declined in the treatments at P = 0.001. Pod numbers and weights as a measure of reproductive potential declined in the plants under flood conditions. CONCLUSIONS: This study confirmed that the soybean plant during the reproductive period is highly sensitive to flooding. Flood-resistant cultivar should be encouraged by farmers to improve crop productivity and food security. FUNDING SOURCES: United State Soybean Production Board USAID.

Interactive effects of multiple environmental stresses are predicted to have a negative effect on cotton growth and development and these effects will be exacerbated in the future climate. The objectives of this study were to test the hypothesis that cotton cultivars differ in their responses to multiple environmental factors of (CO2) [400 and 750 µmol·mol–1 (+(CO2)], temperature [28/20 and 20/12°C (–T)], and UV–B radiation [0 and 10 kJ·m–2·d–1 (+ UV–B)]. A genetic and molecular standard (TM-1) and three modern cotton cultivars (DP1522B2XF, PHY496W3R, and ST4747GLB2) were grown in eight sunlit, controlled environment chambers with control treatment 400 µmol·mol–1 [CO2], 28/21°C temperature, and 0 kJ UV–B. The results showed significant differences among the cultivars for most of the shoot and root parameters. Plants grown under low temperature alone or as a combination with + UV–B treatment caused more detrimental effects on root and shoot vigor. Although the elevated CO2 treatments weakened the damaging effects of higher UV–B levels on cotton growth on all cultivars, increased CO2 could not mask the negative effects of low temperature. When comparing all cultivars, genetic standard TM-1 produced the smallest values for the majority of traits under CO2, UV–B, and low temperature either alone or in combination with other treatments. Based on principal component analysis, the four cultivars were classified as tolerant (DP1522B2XF), intermediate (PHY496W3R and ST4747GLB2) and sensitive (TM-1) to multiple environmental stresses.Low temperature was identified as the most damaging treatment to cotton early seedling vigor while elevated CO2 caused the least. Existing variability of cotton cultivars in response to multiple environmental stresses could allow for selection of cultivars with the best coping ability and higher lint yield for future climate change environments.

Global food demand has risen continuously because of increasing population with greater food and energy needs. Corn production, however, is constrained by current and possible increased future vari...

Early planting of corn ( Zea mays L.) is a strat - egy to avoid excessive heat and drought that often negatively influence grain production dur - ing its reproductive phase. An experiment was conducted by imposing very low (day/night, 21/13°C), low (25/17°C), and optimum (29/21°C) temperatures during seed germination and seedling growth stages under optimum mois - ture and nutrient conditions. Above- and below - ground growth parameters were assessed at 18 d after seeding. Several root morphological traits were assessed using the Win rHIZo root image analysis system. Corn hybrids varied sig nificantly for many traits measured, particularly plant component weights and root morphologi - cal parameters. p rincipal component analysis (pCA) and total low-temperature response index (TLTrI) methods were used to categorize corn hybrid tolerance to low temperature and to group corn hybrids as cold tolerant, moder - ately cold tolerant, moderately cold sensitive, and cold sensitive. Total leaf and root weights and cumulative root length and length per unit volume were the most important morphologi - cal traits in describing hybrid tolerance to cold temperature. Based on the TLTrI method, relative scores were provided for each hybrid, which ranged from 22.45 to 29.52 among the hybrids. The hybrids C8410VT3p, D57Vp51, and r22BHr43 were classified as cold sensitive and Ar1262, DKC6697, DKC6804, and M2V707 as cold tolerant based on p CA and TLTrI tech- niques. Based on the relative scores assigned in this study, corn producers could select hybrids to maximize corn production in an early planting production system.

Development of rapid and inexpensive screening tools for heat and drought stress tolerance is needed and will be helpful in cotton breeding programs and selecting cultivars for a niche environment. In this study, several pollen-based traits at optimum and high temperatures and physiological parameters measured during the boll-filling period were used to evaluate variability among the cultivars for heat and drought stresses. Principal component analysis and drought stress response index methods were used to categorize cotton cultivars into three heat and drought tolerant clusters. Based on the combined analysis, PX532211WRF has been identified as heat- and drought-tolerant, and would be expected to perform better under both heat- and drought-stressed environments. A poor correlation between reproductive and physiological indices indicates that screening breeders have to use different traits to screen cultivars for reproductive and vegetative tolerance. Identified traits could serve as valuable screening tools in cotton breeding programs aimed at developing genotypes to a changing climate. Moreover, cultivar-dependent relative scores will aid in the identification of cultivars best suited to niche environments to alleviate the influences of abiotic stresses at both vegetative and reproductive stages.