Measuring the soil water content (SWC) is a fundamental component of the sustainable management of water resources, soil preservation, and high irrigation efficiency. Non-destructive SWC measurements ...using soil moisture sensors (SMSs) enables timely irrigation and reduces overirrigation and water stress. Within this context, the performance of four commercial single-point soil moisture sensors (Watermark and tensiometer (Irrometer Company, Inc., Riverside, CA, USA), SM150 (Delta-T Devices, Cambridge, UK)), FieldScout TDR300 (Spectrum Technologies, Aurora, IL, USA) and one soil profile PR2 probe (Delta-T Devices, Cambridge, UK) were tested under anthropogenic eutric cambisol with a silty clay loamy texture (20, 30, and 40 cm) to evaluate accuracy and sensitivity to changes in the SWC in an irrigated apple orchard. The Watermark and tensiometer were additionally tested in the laboratory to convert soil water tension (kPa) to the volumetric soil water content (%vol.). In general, all tested SMSs responded to changes in the SWC, with sensor-to-sensor differences. The Watermark and tensiometer underestimated the SWC, while the TDR overestimated the SWC. The SM150 and PR2 showed high accuracy, i.e., SM150—RMSE-2.24 (20 cm), 2.18 (30 cm) and 2.34 (40 cm), MSE—5.02 (20 cm), 2.93 (30 cm) and 1.89 (40 cm), and PR2—RMSE-1.8 (20 cm), 1.3 (30 cm) and 1.55 (40 cm), MSE-3.23 (20 cm), 1.7 (30 cm) and 2.39 (40 cm) at all observed soil depths.
As most of the soybean in Europe is grown in rainfed conditions, climate aberrations are causing significant crop yield variability. To stabilise the yield and shift the sources of supply to ...European-grown soybean, stable and adaptable cultivars must be created by breeding. To better understand the mechanism of drought tolerance in specific germplasm, more knowledge needs to be acquired by research. Therefore, this research aimed to examine the physiological insights on soybean response to drought exposed plants (50% available water holding capacity) by monitoring the relative water content (RWC), lipid peroxidation (TBARS), pigments (Chl a and b), proteins and photosynthetic efficiency during five days in the pod stage. The decrease of RWC in both tested genotypes due to the drought effect, coupled with TBARS increase, indicates lipid peroxidation, which resulted in photosynthetic pigment and protein changes. Most of the chlorophyll a fluorescence parameters suggested plants initiated a defence mechanism to water deficiency, i.e. there was an initial adjustment on the first and second day of drought exposed plants, followed by drastic changes in electron flow in photosystem II (PSII). According to the correlation analysis, the effect of drought was prevalent for Chl b, Chl a/b, relative variable fluorescence at 30 ms (VI), the density of reaction centres (RC/CS0), absorption, trapping, electron transport and dissipation flux per reaction centre (ABS/RC, TR0/RC, ET0/RC and DI0/RC), plastoquinone at quinone A binding niche reducing RCs per PSII antenna chlorophylls (RC/ABS) and performance index (PIABS), meaning these parameters are good indicators of drought stress, that can facilitate the selection of genotypes and increase the efficiency of breeding programmes. Among tested materials, Korana had lower sensitivity to drought and smaller reduction of yield components than OS-211, indicating a better response of its defence mechanism to oxidative stress caused by lack of water. The methods tested and confirmed in this research could be used for screening large numbers of genotypes to determine in the soybean breeding programs aiming to select superior genotypes adaptable to weather changes.
•Lack of water caused a decrease in leaf water content, lipid peroxidation, changes in photosynthetic pigments and proteins.•Chlorophyll a fluorescence is a reliable method for physiological soybean screening under water deficit.•Tested parameters are good indicators of drought stress that can increase the efficiency of breeding programmes.
This study examined the photosynthetic responses of two sunflower hybrids to elevated temperatures and excess light intensity in the flowering stage by measuring the chlorophyll a fluorescence (ChlF) ...under morning and afternoon field conditions to determine the photosynthetic pigment contents and the relative accumulation of photosynthetic proteins. The morning environmental conditions were considered optimal, while the afternoon was characterised by elevated temperatures and excess light intensity. The minimum fluorescence intensity (F0), the electron-flux-reducing end electron acceptors at the photosystem I acceptor side per reaction centre (RE0/RC), and the D1 protein had significant, high, and positive correlations with the environmental conditions, which indicates that they were the most useful in the sunflower-stress-response research. In hybrid 7, the elevated temperatures and the excess light intensity resulted in the inactivation of the oxygen-evolving complex, which was indicated by the positive L, K, and J steps, the increase in the maximum quantum yield of PSII (TR0/ABS), the decrease in the electron transport further than the primary acceptor QA (ET0/(TR0-ET0)), the reduction in the performance index (PIABS), and the higher relative accumulation of the light-harvesting complex of the photosystem (LHCII). Hybrid 4 had smaller changes in the fluorescence curves in phases O–J and J–I, and especially in steps L, K, J, and I, and a higher PIABS, which indicates a more efficient excitation energy under the unfavourable conditions. As the tested parameters were sensitive enough to determine the significant differences between the sunflower hybrids in their photosynthetic responses to the elevated temperatures and excess light intensity in the flowering stage, they can be considered useful selection criteria. The development of more adaptable sunflower hybrids encourages sustainable sunflower production under stressful growing conditions.
Mitigating the effects of changing climate with adaptable cultivars while reducing the input burden of additional selection criteria is becoming a priority, especially as water shortage is limiting ...soybean production in Europe. To evaluate the functionality of the photosynthetic apparatus in drought, chlorophyll a (Chl a) fluorescence was measured in 16 elite soybean lines in drought and conditions with sufficient water supply in V2 (second node), R1 (beginning bloom), R4 (full pod), R5 (beginning seed) and R6 (full seed) stages. Developmental stage was a significant source of variation for all parameters, and PItotal was chosen as the most sensitive parameter in detecting the average drought effect. Genotypes G5, G9, and G10 had superior overall functioning of the photosynthetic apparatus in drought, while the photosynthetic apparatus of G12 and G16 was the least functional. The drought effect was determined to be the most relevant in R1, R4 and R6. G14 had highest PItotal in drought conditions in R1 and R4, while G9 had the highest drought-stressed PItotal in R6. G7 had the lowest drought-stressed PItotal in R1, G4 and G6 had the lowest in R4, and G8 had the lowest in R6. PItotal proved useful in breeding for abiotic stress tolerance, especially for excluding the material with the poorest photosynthetic apparatus function, which increases the efficiency of the selection process when a large number of genotypes needs to be screened. However, genotypes with superior photosynthetic apparatus functioning should be further tested in yield trials to confirm their drought tolerance and value for use in drought conditions.
This study aimed to investigate the impact of cold stress and priming on photosynthesis in the early development of maize and soybean, crops with diverse photosynthetic pathways. The main objectives ...were to determine the effect of cold stress on chlorophyll
fluorescence parameters and spectral reflectance indices, to determine the effect of cold stress priming and possible stress memory and to determine the relationship between different parameters used in determining the stress response. Fourteen maize inbred lines and twelve soybean cultivars were subjected to control, cold stress, and priming followed by cold stress in a walk-in growth chamber. Measurements were conducted using a portable fluorometer and a handheld reflectance instrument. Cold stress induced an overall downregulation of PSII-related specific energy fluxes and efficiencies, the inactivation of RCs resulting in higher energy dissipation, and electron transport chain impairment in both crops. Spectral reflectance indices suggested cold stress resulted in pigment differences between crops. The effect of priming was more pronounced in maize than in soybean with mostly a cumulatively negative effect. However, priming stabilized the electron trapping efficiency and upregulated the electron transfer system in maize, indicating an adaptive response. Overall, this comprehensive analysis provides insights into the complex physiological responses of maize and soybean to cold stress, emphasizing the need for further genotype-specific cold stress response and priming effect research.
The reason for this examination is today’s wide usage of chlorophyll a fluorescence (ChlF) among researchers worldwide to measure photosynthetic efficiency. Although the instructions of the ChlF ...measuring device clearly emphasize the need for methodology adjustments, depending on the specific plant species, many researchers use the usual 30 min of dark adaptation before measurement. Namely, before any ChlF measurement, it is necessary to determine the specific duration of the leaf adaptation to the conditions of darkness of each plant tissue. Because of the numerous uses of the ChlF measurements, we decided to conduct this research to determine whether the appearance of the curves and parameter values depend on the time of sunflower leaf tissue adaptation to dark conditions. Therefore, this research aimed to examine the optimal adaptation time of sunflower tissue to dark conditions to obtain timely precise measurements and credible appearance of ChlF transient curves as well as accurate parameter values. The research was carried out on the sunflower hybrid Luka with 0, 15, 30, 45, 60, 75 and 90 min of dark adaptation in the vegetative, budding and flowering stages in the field conditions. According to the analyzed transient curves and parameters, it was determined that sunflower leaves should be kept in dark conditions for at least 15 min before the measurement of ChlF, which leads to the complete oxidation of PSII and the electron transport chain prior to a saturating pulse of light.
Given the great potential of soybean (Glycine max (L.) Merr.) as a staple crop for food, feed and pharmaceutical industry, improving the genetic basis of seed quality is one of the main breeding aims ...on a global scale. An important quality trait is saccharide composition since it affects digestibility and nutritional value of soybean seed, affecting the usability of this agricultural commodity. This 3-year research (2010-2012) investigated soybean variability by measuring saccharide contents (glucose, fructose, sucrose, raffinose, stachyose) in high-yielding genotypes (maturity groups 00-II) suitable for almost all European regions, while taking into consideration the effect of weather conditions. Statistical analyses included calculating the basic measures of descriptive statistics, analysis of variance (ANOVA), determining correlation and using the Nearest Neighbour clustering to construct a dendrogram based on the Euclidean distance. Results showed the existence of diversity in saccharide content with the influence of genotype, year and their interaction being statistically significant. The lack of correlation between investigated parameters indicates the use of indirect selection is not possible. Nevertheless, the determined divergence indicates the given set of genotypes is suitable for use in future crossing programmes aiming to produce cultivars with more beneficial sugar content in comparison to the existing ones.
This four-year study with four elite soybean lines with different maturities was conducted to investigate the impact of deficit (a field water capacity, or FWC, of 60%) and full irrigation (an FWC of ...80–100%) on soybean grain yield and grain quality (grain protein and oil contents and crude protein and oil yields), depending on the environmental conditions and genotype. Overall, the irrigation effect was positive for the grain yield and grain protein content but negative for the grain oil content. The differences between the full and deficit irrigation were only 2.9% for the grain yield, 2.8% for the crude protein yield and 1.7% for the crude oil yield. The results indicate that deficit irrigation could be the best option for optimizing soybean production in environments similar to the tested one. In such conditions, further rationalization of soybean production could be achieved by choosing the C2 genotype (0 maturity group), which, combined with deficit irrigation, had the highest grain, crude protein and crude oil yields.
Global warming and the associated climate change are imposing abiotic stress on plants. Abiotic factors are crucial for plant productivity, survival, and reproduction. Eight sunflower hybrids were ...tested in conditions of different water availability and with combinations of different temperatures and irradiation. The changes in the photosynthetic efficiency were measured in the morning (control conditions: 2013, 25.8 °C and 349.1 W m−2; 2014, 21.8 °C and 296.4 W m−2) and afternoon (the combination of increased temperatures and high irradiation: 2013, 34 °C and 837.9 W m−2; 2014, 29.4 °C and 888.9 W m−2) at a flowering stage in rainfed or irrigated conditions. The measurement time (morning and afternoon conditions) had a statistically significant effect on all the tested parameters. The performance index (PIABS) in 2013 and the maximum quantum yield of photosystem II (TR0/ABS) in 2014 are the only parameters significantly affected by the irrigation. As a result of the combined effect of increased temperatures and high irradiation, PIABS values decreased by 73–92% in rainfed conditions and by 63–87% in irrigated conditions in 2013, depending on the hybrid, while in 2014, the decrease varied between 70 and 86%. The TR0/ABS decrease was 7–17% in 2013, depending on the hybrid, and 6–12% in 2014, both in rainfed and irrigated conditions. The principal component analysis confirmed the effect of the combination of increased temperatures and high irradiation on hybrids, sorting them exclusively according to the time of measurement. All investigated parameters highly fluctuated between hybrids but without observable trends for the morning and afternoon conditions, as well as for irrigation. Plants’ reaction to the combination of increased temperatures and high irradiation manifested as a change in their photosynthetic efficiency, i.e., the photosynthetic apparatus’ functioning was impaired.
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