Plant Canopy Temperature Research Articles

Estimation of Heritability, Genetic Advance and Correlation in Bread Wheat (Triticum aesitvum L.) under Heat Stress Condition

The current study was conducted on several genotypes during crop season of Rabi 2021-2022 and 2022-2023 with the goal of to work out heritability in general and genetic advance in percentage of mean and estimate correlation coefficient among the growth and yield traits. The field experiments included 60 germplasms of bread wheat. Experimental trials were conducted in 12 environments (E1 to E12). The field experiments were laid out in Augmented Block Design (ABD). The observations on 26 physio-morphological and yield related traits were recorded in both non-stressed and heat-stressed environment. High genotypic and phenotypic coefficients of variation were observed for plant waxiness (8.897 and 11.943) followed by leaf rolling (6.390 and 12.240). Heritability coupled with genetic advance were identified in yield per plot (g), grain yield / plant (g), plant waxiness (0-10 scale). Grain yield per plant exhibited significant positive correlation with grain length (0.712), harvest index (0.629), leaf rolling (0.4638). It exhibited significant negative correlation with plant height (-0.461) and canopy temperature depression (-0.233).

High Throughput Image-Based Phenotyping for Determining Morphological and Physiological Responses to Single and Combined Stresses in Potato.

High throughput image-based phenotyping is a powerful tool to non-invasively determine the development and performance of plants under specific conditions over time. By using multiple imaging sensors, many traits of interest can be assessed, including plant biomass, photosynthetic efficiency, canopy temperature, and leaf reflectance indices. Plants are frequently exposed to multiple stresses under field conditions where severe heat waves, flooding, and drought events seriously threaten crop productivity. When stresses coincide, resulting effects on plants can be distinct due to synergistic or antagonistic interactions. To elucidate how potato plants respond to single and combined stresses that resemble naturally occurring stress scenarios, five different treatments were imposed on a selected potato cultivar (Solanum tuberosum L., cv. Lady Rosetta) at the onset of tuberization, i.e. control, drought, heat, waterlogging, and combinations of heat, drought, and waterlogging stresses. Our analysis shows that waterlogging stress had the most detrimental effect on plant performance, leading to fast and drastic physiological responses related to stomatal closure, including a reduction in the quantum yield and efficiency of photosystem II and an increase in canopy temperature and water index. Under heat and combined stress treatments, the relative growth rate was reduced in the early phase of stress. Under drought and combined stresses, plant volume and photosynthetic performance dropped with an increased temperature and stomata closure in the late phase of stress. The combination of optimized stress treatment under defined environmental conditions together with selected phenotyping protocols allowed to revealthe dynamics of morphological and physiological responses to single and combined stresses. Here, a useful tool is presented for plant researchers looking to identify plant traits indicative of resilience to several climate change-related stresses.

Application of mycorrhizae and rhizobacteria inoculations in the cultivation of processing tomato under water shortage

The effect of mycorrhizal fungi and plant growth promoting rhizobacteria on some physiological properties, yield and soluble solid content (Brix) of ‘Uno Rosso’ F1 processing tomato was studied under water scarcity. Inoculation was performed with mycorrhizal fungi (M) and rhizobacteria preparation (PH) at sowing (M1, PH1) and sowing + planting (M2, PH2). The treated and untreated plants were grown with regular irrigation (RI = ET100%), with deficit irrigation (DI = ET50%) and without irrigation (I0). In drought, the canopy temperature of plants inoculated with arbuscular mycorrhizal fungi (M1, M2) decreased significantly, however, the decrease was small in those treated with the bacterium (PH1, PH2), while the SPAD value of the leaves of plants treated only with Phylazonit increased significantly. On two occasions, inoculations (M2, PH2) significantly increased the total yield and marketable yield, however, under water deficiency, a higher rate of green yield was detected than untreated plants. In dry year using deficit irrigation, the one-time inoculation (M1, PH1) provided a more favorable Brix value, while the double treatments reduced the Brix. In moderate water scarcity, the use of mycorrhizal inoculation (M2) is preferable, while under weak water stress, the use of rhizobacteria inoculation (PH2) is more favorable.

Modelling weed seed predation by carabids and its effects on crop production under contrasted farming systems

To reduce herbicide use, different avenues of biological weed regulation are currently investigated. Among these, weed seed predation by carabid beetles appears promising. Though observed in different cropping systems and conditions in fields, there was to date no demonstration that this process actually influences weed dynamics over time and reduces weed harmfulness for crop production. Consequently, the objective of the present paper was to (1) model the impact of cropping system, field margin and pedoclimate on weed seed predation by carabids to complete the FlorSys model, which simulates weed dynamics and crop production from cropping systems, soil and weather, (2) evaluate whether including seed predation is needed to correctly predict weed dynamics in different cropping systems, (3) which components of the seed predation submodel are the most influential. The new seed-predation submodel calculates the daily predation rate for each weed species from seed traits, weather data, canopy state variables and management operations. In FlorSys, this predation rate is applied to the newly shed weed seeds on the soil surface. The equations and parameters were based on past publications from our team and other literature. Then, simulations were run with FlorSys over 13 years, with and without the seed predation submodel, using weather data and management operations from 10 fields from the INRAE Dijon-Epoisses experimental station. The resulting output in terms of weed and crop state variables (plant density, biomass, seed bank, yield) were compared to measurements from the 10 fields, showing that including weed seed predation in the simulations improved the model's prediction quality, by reducing the overestimation in weed-variable predictions. Finally, a sensitivity analysis to the components of the predation submodel was run, by repeating the simulations after successively switching off individual components of the submodel. This showed that daily incident radiation, light interception by plant canopy, harvest, carabid reproduction and daily temperature had the most influence on seed predation rates. The simulations showed that weed seed predation by carabids can indeed contribute to managing weeds, by reducing field infestation and improving crop yields, but with large variations among crops. However, to determine which cropping systems and field margins favour weed seed predation enough to noticeably contribute to biological weed regulation, a larger diversity of cropping systems and weather series needs to be explored by simulation.

Plant canopies exhibit stronger thermoregulation capability at the seasonal than diurnal timescales

Plant canopy temperature (Tc) plays a crucial role in regulating plant growth and metabolism. Although dominant controls on Tc are observed to differ across timescales, whether this would cause differences in plant thermoregulation capability (PTC) remains unclear, raising concerns about extrapolating findings on plant thermoregulation from one timescale to another. Here we constructed diurnal and seasonal datasets of Tc, air temperature (Ta), and other biotic and abiotic factors from global hourly flux data, and explored diurnal and seasonal variations in PTC (indicated by Tcvs. Ta regression slope, with lower slopes indicating higher Tc stability and stronger thermoregulation). Our result revealed significantly lower Tcvs. Ta slopes (i.e. stronger PTC) at seasonal than diurnal timescales, primarily due to different transpiration cooling at high Ta between the two timescales. At the diurnal timescale, transpiration rates initially increase before decreasing with Ta after reaching a specific temperature threshold (∼85th percentile of Ta; related to midday depression of stomatal activities); Conversely, at the seasonal timescale, transpiration rates consistently increase with Ta (related to the coincidence among high water availability and the peak annual Ta). PTC also displays considerable spatial variability, with latent heat vs. net radiation relationship and water availability being the dominant regulators. Collectively, we recommend caution when extrapolating thermoregulation-relevant conclusions drawn from short-term observations to longer-term predictions, and vice versa, since they have different patterns and underlying mechanisms.

Polyethylene glycol-induced drought stress screening of selected Philippine high-yielding sugarcane varieties

A greenhouse study was conducted to characterize the drought response of eight high-yielding sugarcane varieties at tillering stage using polyethylene glycol 6000 (PEG6000) induced drought conditions. Plant height, stalk diameter, dry matter accumulation, root characteristics, stomatal conductance, chlorophyll fluorescence, SPAD, normalized difference vegetation index (NDVI), and canopy temperature were evaluated at 2.5 months after planting after four weeks of induced drought conditions. The study aimed to determine whether 1.0% PEG treatment would be able to produce significant differences among test genotypes and use it as a basis to determine drought-tolerant and susceptible varieties. Significant differences were observed among genotypes in PEG stress treatments. PEG stress resulted in significant reductions relative to non-PEG treatment in plant height (32.1%), leaf dry matter (31.6%), and stalk dry matter (49.5%) while total root length (11.8%), root surface area (7.8%) and root volume (19.6%) have generally increased. Reduced plant height, stalk diameter, and dry matter accumulation were observed in susceptible genotypes, while potential tolerant lines maintained or exhibited less reduction in these traits. Moreover, principal component analysis suggests that stalk dry matter, stomatal conductance, chlorophyll fluorescence plant height, SPAD, canopy temperature, and NDVI, highly contributed to the overall variation in the data (41.5%). With this, vars. 2289, 1011, 2569, and 1899 were identified to be potential drought-tolerant varieties while vars. 1763 and 2155 were potential drought susceptible varieties. Screening for drought tolerance under controlled conditions using PEG-induced drought stress offers a promising approach for sugarcane breeding especially when focusing on specific drought responses during important formative stages such as tillering stage. Being able to select genotypes of interest as early as the tillering stage would significantly hasten breeding cycles and will highly benefit the efforts towards drought stress tolerance in sugarcane.

Spatial corn canopy temperature extraction: How focal length and sUAS flying altitude influence thermal infrared sensing accuracy

Irrigation water management starts with quantifying irrigation prescriptions based on crop water requirements at a spatial scale. The most accepted and effective method for estimating this water need is to use the canopy temperature of the plants. The use of small unmanned aerial systems (sUAS) with a thermal infrared camera has long been established as an effective method of measuring plant canopy temperatures at a spatial scale. However, concerns still exist about the accuracy of canopy temperatures collected by these systems and how imagery collection altitude or camera viewing angle affects the temperature estimation. To address these concerns, this study was designed to evaluate the effects of flying altitude of airborne thermal infrared (TIR) imagery and camera view angle on corn-canopy temperature sensing accuracy and image quality. Three different thermal cameras with focal lengths of 9 mm, 13 mm, and 19 mm were used, and each camera was flown at an altitude of 30 m, 50 m, and 70 m. Thermal cameras were mounted on an sUAS and flown over a 6000 m2 cornfield. The sUAS was flown at a speed of 3 m/s on autopilot mode guided by pre-planned missions. The thermal camera was triggered once per second, and imagery was geotagged using an external GPS unit. Images obtained using different combinations of focal lengths and flight altitudes were processed and converted into orthomosaics. Calibration was conducted using ground-based temperature reference panels and temperature maps were created from the orthomosaics. The orthomosaics were examined for the accuracy of the corn-canopy temperature sensing, ability to differentiate between hot and cold surfaces, ease of image stitching/developing orthomosaics, geometric accuracy, image quality, and spatial resolution. The results indicated that with the combination of appropriate camera focal length, altitude, and image calibration techniques, a canopy temperature map of crops with a temperature error of less than 2 °C from the actual canopy temperature can be produced. A narrow-angle thermal camera flying at low altitudes (<50 m) was found to be the least suitable combination for corn canopy temperature sensing. The most appropriate combination for temperature estimation of corn canopies was with a 13 mm focal length camera flying at an altitude of 50 m above ground level.

Carbon isotope discrimination as a key physiological trait to phenotype drought/heat resistance of future climate-resilient German winter wheat compared with relative leaf water content and canopy temperature.

Climate change is expected to influence crop growth through frequent drought and heat extremes, and thus, drought and heat tolerance are of increasing importance as major breeding goals for cereal crops in Central Europe. Plant physiological water status traits are suitable for phenotyping plant drought/heat tolerance. The objective of this study was to determine whether relative leaf water content (RLWC), plant canopy temperature (CT), and carbon isotope discrimination (CID) are suitable for phenotyping the drought/heat resistance of German winter wheat for future climate resilience. Therefore, a comprehensive field evaluation was conducted under drier and warmer conditions in Moldova using a space-for-time approach for twenty winter wheat varieties from Germany and compared to twenty regionally adapted varieties from Eastern Europe. Among the physiological traits RLWC, CT, and CID, the heritability of RLWC showed the lowest values regardless of year or variety origin, and there was no significant correlation between RLWC and grain yield regardless of the year, suggesting that RLWC did not seem to be a useful trait for distinguishing origins or varieties under continental field conditions. Although the heritability of CT demonstrated high values, the results showed surprisingly low and nonsignificant correlations between CT and grain yield; this may have been due to a confounding effect of increased soil temperature in the investigated dark Chernozem soil. In contrast, the heritability of CID in leaves and grain was high, and there were significant correlations between grain yield and CID, suggesting that CID is a reliable indirect physiological trait for phenotyping drought/heat resistance for future climate resilience in German wheat.

What lies beneath: Vertical temperature heterogeneity in a Mediterranean woodland savanna

As the availability of satellite and airborne thermal infrared remote sensing (TIR-RS) data increases and their spatial, temporal, and spectral resolutions improve, researchers are finding diverse applications for TIR-RS measurements. TIR-RS is now commonly applied in regional- and continental-scale analyses, such as those focused on fire and surface energy balance. However, its application lags in plant physiology and ecology, for which a finer-scale understanding of plant canopy temperatures would be useful to elucidate plant water dynamics, for example. In particular, while methods to disaggregate TIR-RS pixels in horizontal space have advanced, possible vertical stratification of plant canopy temperature and its implications for understanding the correspondence between TIR-RS and finer-scale, field-based thermal measurements (e.g. made with a thermal camera) remain unexplored. Here, we use data from a thermal camera deployed concurrently with the recent ECOSTRESS mission to quantify vertical temperature gradients within tree canopies and temperatures of over- vs. under-story plants in a Mediterranean woodland savanna. We then leverage diverse ancillary data to maximize the geometric comparability of ECOSTRESS and thermal camera measurements, in order to assess the extent to which the two forms of thermal measurements correspond. Specifically, we ask: (1) What are the patterns of intra-canopy and over- vs. under-story vertical temperature in a Mediterranean woodland savanna?, and (2) How can vertically-resolved, but spatially-limited field-based temperature measurements be reconciled with spatially-extensive, but surface-only, temperature measurements of a space-borne remote sensor? We found consistent patterns of vertical thermal heterogeneity both within tree canopies and between ecosystem over- and under-stories. The daytime difference between the top and bottom thirds of blue oak canopies was, on average, 0.48 ° C – and sometimes several times larger. Notably, canopy tops are cooler, likely associated with the under-story grass reaching daytime temperatures often exceeding over-story temperatures by 10° C. Given the consistency of the intra-canopy temperature gradients, we expected the ECOSTRESS sensor would be in better agreement with camera measurements of canopy tops than bulk canopies or canopy bottoms. However, within-canopy gradients were overwhelmed by other sources of disagreement between the measurements, in part associated with upscaling camera measurements across space. Overall, thermal camera and ECOSTRESS measurements were largely in agreement at night (pixel RMSE = 1.1°C), but they were more divergent during times of low (but >0 W/m2) and high incoming solar radiation (daytime pixel RMSE = 3.5°C).

Cooler canopy leverages sorghum adaptation to drought and heat stress

In the present study, individual and combined effects of drought and heat stress were investigated on key physiological parameters (canopy temperature, membrane stability index, chlorophyll content, relative water content, and chlorophyll fluorescence) in two popular sorghum cultivars (Sorghum bicolor cvs. Phule Revati and Phule Vasudha) during the seedling stage. Estimating canopy temperature through pixel-wise analysis of thermal images of plants differentiated the stress responses of sorghum cultivars more effectively than the conventional way of recording canopy temperature. Cultivar difference in maintaining the canopy temperature was also responsible for much of the variation found in critical plant physiological parameters such as cell membrane stability, chlorophyll content, and chlorophyll fluorescence in plants exposed to stress. Hence, the combined stress of drought and heat was more adverse than their individual impacts. The continued loss of water coupled with high-temperature exposure exacerbated the adverse effect of stresses with a remarkable increase in canopy temperature. However, Phule Vasudha, being a drought-tolerant variety, was relatively less affected by the imposed stress conditions than Phule Revati. Besides, the methodology of measuring and reporting plant canopy temperature, which emerged from this study, can effectively differentiate the sorghum genotypes under the combined stress of drought and heat. It can help select promising genotypes among the breeding lines and integrating the concept in the protocol for precision water management in crops like sorghum.

Remote sensing devices as key methods in the advanced turfgrass phenotyping under different water regimes

Turfgrass phenotyping is a potential tool in different grass program breeding. The traditional methods for turfgrass drought phenotyping in field are time-consuming and labor-intensive. However, remote sensing techniques emerge as effective, rapid and easy approaches to optimize turfgrass selection under water stress. Remote sensing approaches are considerate as important strategies to select species of turfgrass tolerable to drought allowing green space sustainability and environment protection in regions with water limitation. Here we evaluated differences between six mixtures of C3-C4 turfgrass grown under two water regimes (limited and high irrigation). The performance of turf species was achieved using the green area (GA) vegetation index calculated from RGB (red green, blue) images obtained by ground camera and drone imagery, the normalized difference vegetation index (NDVI), the plant canopy temperature (CT) and soil moisture content (SM). Both vegetation (GA and NDVI) and water status (CT and SM) indices presented a significant difference in turfgrass growth under the two water regimes. Differences among turfgrass species were detected under limited and high irrigation using the vegetation indices. Both NDVI and GA allowed clear separation between drought-tolerant and susceptible turfgrass, as well as the identification of the mixtures with a rapid green regeneration after a period of limited irrigation. Moreover, the canopy temperature also discriminated between turfgrass species but only under limited irrigation, while soil moisture values did not differentiate between species. Furthermore, the regression and conceptual model using remote sensing parameters revealed the most adequate criteria to detect turfgrass variability under each growing condition. This study also highlights the usefulness of green area vegetation index derived from drone imagery. GA obtained by drone images in this study explained turfgrass variability better than that derived from ground RGB images or the NDVI.

Energy Minimisation in a Protected Cropping Facility Using Multi-Temperature Acquisition Points and Control of Ventilation Settings

Energy management in protected cropping is critical due to the high cost of energy use in high-tech greenhouse facilities. The main purpose of this research was to investigate the optimal strategy to reduce cooling energy consumption, by regulating the settings (opening/closing) of either vents or curtains during the day, at the protected cropping facility at Western Sydney University. We measured daily changes in air temperature and energy consumption under four treatments (open/closed combinations of vents and shade screens) and developed an optimal cooling strategy for energy management using multi-temperature acquisition points at different heights within a greenhouse compartment. The optimal treatment (vents open/curtains closed) reduced energy load at the rooftop, thereby maintaining a desirable plant canopy temperature profile, and reducing cooling energy. Daily energy consumption was lowest for vents open/curtains closed (70.5 kWh) and highest for vents closed/curtains open (121 kWh). It was also found that delaying the operation of opening and closing of vents and curtains until the plant canopy temperature reached 25 °C reduced cooling energy consumption and decreased heating energy consumption in the morning (e.g., 08:00 to 10:00). The estimated savings of 1.83 kWh per 1 °C cooling between the optimal (vents open/curtains closed) and least optimal (vents closed/curtains open) conditions had the potential for significant energy savings at 494 kWh per °C over a crop cycle of nine months in warm weather conditions. However, selection of the optimal cooling strategy utilising control of vents and curtains must also account for the impact from other greenhouse environmental factors, including light, humidity, and CO2 concentration, which may be crop specific.

Use of Thermal Imaging to Assess Water Status in Citrus Plants in Greenhouses

The direct examination of plant canopy temperature can assist in optimizing citrus irrigation management in greenhouses. This study aimed to develop a method to measure canopy temperature using thermal imaging in one-year-old citrus plants in a greenhouse to identify plants with water stress and verify its potential to be used as a tool to assess citrus water status. The experiment was conducted for 48 days (27 November 2019 to 13 January 2020). We evaluated the influence of five levels of irrigation on two citrus species (‘Red Ruby’ grapefruit (Citrus paradisi) and ‘Valencia’ sweet orange (Citrus sinensis (L.) Osbeck)). Images were taken using a portable thermal camera and analyzed using open-source software. We determined canopy temperature, leaf photosynthesis and transpiration, and plant biomass. The results indicated a positive relationship between the amount of water applied and the temperature response of plants exposed to different water levels. Grapefruit and sweet orange plants that received less water and were submitted to water restrictions showed higher canopy temperatures than the air (up to 6 °C). The thermal images easily identified water-stressed plants. Our proof-of-concept study allowed quickly obtaining the canopy temperature using readily available equipment and can be used as a tool to assess citrus water status in one-year-old citrus plants in greenhouses and perhaps in commercial operations with mature trees in the field after specific experimentation. This technique, coupled with an automated system, can be used for irrigation scheduling. Thus, setting up a limit temperature is necessary to start the irrigation system and set the irrigation time based on the soil water content. To use this process on a large scale, it is necessary to apply an automation routine to process the thermal images in real time and remove the weeds from the background to determine the canopy temperature.

Foliar Growth Regulator Sprays Induced Tolerance to Combined Heat Stress by Enhancing Physiological and Biochemical Responses in Rice.

Rice yield has decreased due to climate variability and change in Colombia. Plant growth regulators have been used as a strategy to mitigate heat stress in different crops. Therefore, this study aimed to evaluate the effect of foliar applications of four growth regulators [auxins (AUX), brassinosteroids (BR), cytokinins (CK), or gibberellins (GA)] on physiological (stomatal conductance, total chlorophyll content, Fv/Fm ratio, plant canopy temperature, and relative water content) and biochemical (Malondialdehyde (MDA) and proline contents) variables in two commercial rice genotypes exposed to combined heat stress (high day and nighttime temperatures). Two separate experiments were carried out using plants of two rice genotypes, Fedearroz 67 (“F67”) and Fedearroz 2000 (“F2000”) for the first and second experiments, respectively. Both trials were analyzed together as a series of experiments. The established treatments were as follows: absolute control (AC) (rice plants grown under optimal temperatures (30/25°C day/nighttime temperatures), heat stress control (SC) [rice plants only exposed to combined heat stress (40/30°C)], and stressed rice plants and sprayed twice (5 days before and after heat stress) with a plant growth regulator (stress+AUX, stress+BR, stress+CK, or stress+GA). The results showed that foliar CK sprays enhanced the total chlorophyll content in both cultivars (3.25 and 3.65 mg g−1 fresh weight for “F67” and “F2000” rice plants, respectively) compared to SC plants (2.36 and 2.56 mg g−1 fresh weight for “F67,” and “F2000” rice plants, respectively). Foliar CK application also improved stomatal conductance mainly in “F2000” rice plants compared to their heat stress control (499.25 vs.150.60 mmol m−2s−1). Foliar BR or CK sprays reduced plant canopy temperature between 2 and 3°C and MDA content in plants under heat stress. The relative tolerance index suggested that foliar CK (97.69%), and BR (60.73%) applications helped to mitigate combined heat stress mainly in “F2000” rice plants. In conclusion, foliar BR or CK applications can be considered an agronomic strategy to help to ameliorate the negative effect of combined heat stress conditions on the physiological behavior of rice plants.

Stomatal Traits and Barley (Hordeum vulgare L.) Forage Yield in Drought Conditions of Northeastern Mexico.

Infrared technology is a practical, fast, non-destructive method that helps in forecasting plant development and can be used to select physiological traits, instead of other methodologies that require more time and breeding efforts. According to the statistical analyses and the relationship between the direct and indirect effects of the variables, this technology could serve as the basis for implementing a genotype selection methodology. Awnless barley was assessed in a randomized block design with three replicates in two crop seasons at Mexico’s northeastern region. Two samplings were carried out during crop development: at 75 and 90 days after sowing. The infrared and stomatal sensors were used to identify the direct and indirect effects of stomata’s traits on dry forage yield. The data were analyzed in a subdivided plot design, using mean comparison tests, correlation coefficients and path analyses, finding significant differences (p < 0.05) among localities and among samplings. Dry forage yield was significant and positively correlated with plant height (r = 0.578) and canopy temperature (r = 0.724), and negatively correlated with the leaf upper side stomatal width (r = −0.409) and the leaf lower side stomatal width (r = −0.641), chlorophyll content and vegetation index. Temperature, chlorophyll, density and leaf lower side stomatal index had the strongest direct effects on yield. Therefore, the infrared technology appears as a way to select high yielding awnless forage barley, to obtain the correlation, the positive direct effect of temperature and the negative effect of chlorophyll. Due to their direct effects, low density and low leaf underside stomatal indexes can also help in the indirect selection of higher yielding forage barley genotypes.

Salinity stress effects on transpiration and plant growth under different salinity soil levels based on thermal infrared remote (TIR) technique

Soil salinization is a serious land degradation issue in Northwest China and significantly threatens food security; thus, a comprehensive understanding of plant response to salinity stress is desirable. The objective was to detect the effect of salinity stress on alfalfa transpiration rate and plant growth under four salinity levels. The thermal infrared remote (TIR) technique was used to acquire the canopy temperature of plants exposed to four salinities (no salinity, S0; slight salinity, S3; moderate salinity, S5; and severe salinity, S7), while transpiration was evaluated based on the three temperature (3 T) model. Results indicated that the 3 T model and TIR technique successfully simulated transpiration with a high coefficient determination of R2 above 0.8. The general pattern is that canopy temperature values correspond well with salinity values. With the increase of soil salinity for the treatment of S3, S5, and S7, the canopy temperature increased by 0.88 °C, 0.98 °C, and 1.19 °C, respectively. Moreover, the growth of alfalfa was inhibited, resulting in a corresponding decrease in leaf area index by 19.3%, 31.2%, and 54.2%, respectively. Transpiration reduced by 1.2%, 6.7%, and 20.0%, correspondingly, because of stunted growth and less canopy cover. Salinity stress on agricultural crops was extremely negative; the higher the soil salinity was, the lower the canopy cover, so salinity reduced the growth rate and resulted in reduced plants growing due to osmotic effects. Where salt accumulation occurs in a horizontally nonuniform way, transpiration may be presented by spatial heterogeneity; however, there remains limited research on this issue. This research will provide a scientific basis for ecological construction programs.

Using Thermography to Confirm Genotypic Variation for Drought Response in Maize.

The feasibility of thermography as a technique for plant screening aiming at drought-tolerance has been proven by its relationship with gas exchange, biomass, and yield. In this study, unlike most of the previous, thermography was applied for phenotyping contrasting maize genotypes whose classification for drought tolerance had already been established in the field. Our objective was to determine whether thermography-based classification would discriminate the maize genotypes in a similar way as the field selection in which just grain yield was taken into account as a criterion. We evaluated gas exchange, daily water consumption, leaf relative water content, aboveground biomass, and grain yield. Indeed, the screening of maize genotypes based on canopy temperature showed similar results to traditional methods. Nevertheless, canopy temperature only partially reflected gas exchange rates and daily water consumption in plants under drought. Part of the explanation may lie in the changes that drought had caused in plant leaves and canopy structure, altering absorption and dissipation of energy, photosynthesis, transpiration, and partitioning rates. Accordingly, although there was a negative relationship between grain yield and plant canopy temperature, it does not necessarily mean that plants whose canopies were maintained cooler under drought achieved the highest yield.

Genome-wide association study reveals genomic regions controlling root and shoot traits at late growth stages in wheat.

Background and AimsRoot system morphology is important for sustainable agriculture, but the genetic basis of root traits and their relationship to shoot traits remain to be elucidated. The aim of the present study was to dissect the genetic basis of root traits at late growth stages and its implications on shoot traits in wheat.MethodsAmong 323 wheat accessions, we investigated phenotypic differences in root traits at booting and mid-grain fill stages in PVC tubes, shoot traits including plant height (PH), canopy temperature (CT) and grain yield per plant (YPP) in a field experiment, and performed a genome-wide association study with a Wheat 660K SNP Array.Key ResultsDeep-rooted accessions had lower CT and higher YPP than those with shallow roots, but no significant relationship was identified between root dry weight and shoot traits. Ninety-three significantly associated loci (SALs) were detected by the mixed linear model, among which three were hub SALs (Co-6A, Co-6B and Co-6D) associated with root depth at both booting and mid-grain fill stages, as well as CT and YPP. Minirhizotron system scanning results suggested that the causal genes in the three SALs may regulate root elongation in the field. The heritable independence between root depth and PH was demonstrated by linkage disequilibrium analysis. The YPP was significantly higher in genotypes which combined favourable marker alleles (FMAs) for root depth and PH, suggesting that a deep root and shorter plant height are suitable traits for pyramiding target alleles by molecular marker-assisted breeding.ConclusionsThese results uncovered promising genomic regions for functional gene discovery of root traits in the late growth period, enhanced understanding of correlation between root and shoot traits, and will facilitate intensive study on root morphology and breeding through molecular design.

Spatial Analysis of Soybean Plant Height and Plant Canopy Temperature Measured with On-the-Go Tractor Mounted Sensors

There is a growing interest in the Open Ag community to use inexpensive sensors controlled by open-source software to measure plant height and plant canopy temperature of agricultural crops. Plant height and plant canopy temperature are key indicators of plant health. This research study reports on an ongoing research initiative to test a compact and inexpensive mobile sensor to measure plant height and plant canopy temperature. The system is controlled by open source software and hardware. The specific objectives for this study were to analyze the relationship between plant height and plant canopy temperature of soybeans (Glycine max L.) measured with the mobile system and to analyze the spatial correlation of the plant height and plant canopy temperature measurements. Data were collected in a soybean plot in 2018 and 2019. Descriptive statistics, Pearson correlation, and geostatistical techniques were used to evaluate the data. A negative statistically significant (p ≤ 0.05) relationship was observed between the plant height and the plant canopy temperature measurements (r = −0.54, 2018; r = −0.37, 2019). Also, both parameters were spatially correlated; however, plant height had a greater spatial continuity than plant canopy temperature. Furthermore, similar patterns were observed for the in-field variability of the plant height and plant temperature maps derived via kriging. Similarities in plant height and plant canopy temperatures were observed from one year to the next, suggesting that the sensor technologies could be used as a historical record for monitoring growth patterns in soybean fields. The sensors and techniques used in this study can be easily adapted to other crops, thus providing two important layers for monitoring plant growth and potentially plant stress.

Simple Background Subtraction of Thermal Imagery for Canopy Temperature Measurement in Greenhouse

Abstract. While infrared thermometry and thermal imagery have potential to detect crop water stress and quantify evapotranspiration, both valuable in irrigation scheduling, it is often difficult to isolate plant canopy temperature from background temperatures. In this study, we demonstrate a simple technique that uses a homogeneous background temperature that contrasts with canopy temperature, thereby allowing the canopy temperature itself to be isolated in a thermal image. Analysis of pixel temperatures and their associated statistics demonstrate the potential of this method to measure small (ca. &amp;lt; 0.5°C) and rapid (ca. &amp;lt; 1 s) fluctuations in leaf energy balance. This technique has broad applicability in greenhouse, growth chamber, and other small-scale experiments where real time response of individual leaves or canopies is required. Keywords: Thermal imaging, Crop water stress, Infrared thermometry, Background masking, Deficit irrigation, Greenhouse.