Estimation of leaf water potential by thermal imagery and spatial analysis*

Cohen, Yafit; Alchanatis, V.; Meron, M.; Saranga, Yehoshua; Tsipris, J.

doi:10.1093/jxb/eri174

Cited by 327 publications

(174 citation statements)

References 16 publications

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“…The significance of the observed differences was brought into question, however, after we identified the significant impact of field spatial variability on the overall well being of the cotton within a single variety. The spatial variability of crop water status results from variability of soil, crop canopy, topography, irrigation level (either inherent in the application method or caused by malfunctions), or from other factors such as salinity, which typically is spatially variable (Cohen et al, 2005). The results presented in Figure 9 demonstrate the magnitude of the spatial variability within a relatively small region of the field.…”

Section: Comparison Of Varietal Water-deficit Stress Responsesmentioning

confidence: 98%

Evaluation of Source Leaf Responses to Water-Deficit Stresses in Cotton Using a Novel Stress Bioassay

Burke

2006

Plant Physiology

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Water-deficit stresses preferentially reduce shoot growth, thereby disrupting the flow of carbohydrates from source leaves to the developing sinks. Here, we use a novel stress bioassay to dissect responses of field and greenhouse-grown cotton (Gossypium hirsutum) source leaves to water-deficit stresses. Fifth main stem leaf samples were harvested at sunrise and subjected to a prolonged elevated respiratory demand in the dark. Sucrose levels are lower in nonstressed cotton at sunrise compared to waterdeficit stressed cotton, potentially predisposing the nonstressed tissue to succumb more rapidly. Tissue death was determined initially using the cell viability stain 2,3,5-triphenyltetrazolium chloride, but was determined in subsequent experiments by monitoring the decline in chlorophyll fluorescence yield. Fluorescence yield measurements were obtained within minutes of harvesting and individual samples were monitored over the time course of the treatment. Analyses of the time course and magnitude of chlorophyll fluorescence yield decline in samples from irrigated and dryland plots permitted the detection of stress responses within 24 h of the cessation of irrigation. The rate of fluorescence yield decline during the elevated respiratory demand treatment slowed as the water-deficit stress increased. Upon irrigation, the source leaves of the water-stressed plants recovered to prestress values within 4 d. Well-watered cotton overexpressing heat shock protein 101 had identical rates of fluorescence yield decline as nontransgenic cotton. These results suggest that the delayed decline in fluorescence yield of water-stressed tissue exposed to prolonged elevated respiratory demand can be used as a sensitive indicator of water-deficit stress responses.

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Section: Comparison Of Varietal Water-deficit Stress Responsesmentioning

confidence: 98%

Evaluation of Source Leaf Responses to Water-Deficit Stresses in Cotton Using a Novel Stress Bioassay

Burke

2006

Plant Physiology

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“…The accurate estimate of ETa or latent heat flux (LE) is an important factor for establishing irrigation strategies such as regulated deficit irrigation (RDI), which has been successfully applied on olive orchards to increase water productivity and olive oil quality [7][8][9][10]. In addition, Cohen et al [11] and Ortega-Farias et al [12] indicated that the site-specific irrigation management (SSIM) can be used as a technical tool to improve water productivity. In that case, SSIM characterizes the effect of intra-and inter-field spatial variability of soil and canopy vigor on the estimation of ETa and irrigation scheduling (irrigation frequency and timing).…”

Section: Introductionmentioning

confidence: 99%

Estimation of Energy Balance Components over a Drip-Irrigated Olive Orchard Using Thermal and Multispectral Cameras Placed on a Helicopter-Based Unmanned Aerial Vehicle (UAV)

et al. 2016

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A field experiment was carried out to implement a remote sensing energy balance (RSEB) algorithm for estimating the incoming solar radiation (Rsi), net radiation (Rn), sensible heat flux (H), soil heat flux (G) and latent heat flux (LE) over a drip-irrigated olive (cv. Arbequina) orchard located in the Pencahue Valley, Maule Region, Chile (35˝25 1 S; 71˝44 1 W; 90 m above sea level). For this study, a helicopter-based unmanned aerial vehicle (UAV) was equipped with multispectral and infrared thermal cameras to obtain simultaneously the normalized difference vegetation index (NDVI) and surface temperature (T surface ) at very high resolution (6 cmˆ6 cm). Meteorological variables and surface energy balance components were measured at the time of the UAV overpass (near solar noon). The performance of the RSEB algorithm was evaluated using measurements of H and LE obtained from an eddy correlation system. In addition, estimated values of Rsi and Rn were compared with ground-truth measurements from a four-way net radiometer while those of G were compared with soil heat flux based on flux plates. Results indicated that RSEB algorithm estimated LE and H with errors of 7% and 5%, respectively. Values of the root mean squared error (RMSE) and mean absolute error (MAE) for LE were 50 and 43 W m´2 while those for H were 56 and 46 W m´2, respectively. Finally, the RSEB algorithm computed Rsi, Rn and G with error less than 5% and with values of RMSE and MAE less than 38 W m´2. Results demonstrated that multispectral and thermal cameras placed on an UAV could provide an excellent tool to evaluate the intra-orchard spatial variability of Rn, G, H, LE, NDVI and T surface over the tree canopy and soil surface between rows.

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“…ET o basis irrigation can be applied when no major soil water limit and also, when plant tissues are sufficiently hydrated, which must not always be the case (Cohen et al 2005). Besides, irrigation to maintain non-limiting soil water conditions is not always the best option for water and nutrient management.…”

Section: Resultsmentioning

confidence: 99%

Evaluation of evapotranspiration models for estimating daily reference evapotranspiration in arid and semiarid environments

Mohawesh¹

2011

PLANT SOIL ENVIRON

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145The United Nations of Food and Agricultural Organization (FAO) proposed a methodology for computing crop evapotranspiration (ET o ) and crop coefficient (K c ) (Doorenbos and Pruitt 1977). These coefficients depend on several factors including crop type, stage of crop growth, canopy height and density (Allen et al. 1998). To schedule irrigation properly, an accurate and standard method to estimate ET o to predict crop water requirements, was stated by several authors (Chiew et al. 1995;Allen 1996). A great number of models was developed to estimate ET o for use in environments that lack direct ET o measurements Pruitt 2004, Gavilán et al. 2006). A major complication in ET o estimation using these models is the requirement for meteorological data that may not be easily available. This restriction at times prohibits use of more accurate models, and necessitates the use of models that have less demanding data requirements.An international scientific community has accepted the FAO56 Penman-Monteith (FAO56PM) model as the most precise one for its good results when compared with other models in various regions of the entire world (Chiew et al. 1995, Garcia et al. 2004, Gavilán et al. 2006. Estimation of reference ET o by globally accepted FAO56PM (Allen et al. 1998) requires the weather parameters like maximum and minimum temperature, solar radiation, sunshine hours, wind speed, relative humidity. However, for many locations, as is the case for Jordan, such meteorological variables are often incomplete and/ or not available. Furthermore, no published studies have examined the applicability of ET o models across Jordan, a country with a great gradient in temperature and precipitation. Moreover, the local calibration and validation of other models is more important in semiarid and arid regions than the temperate climate because most of these models were calibrated and validated in temperate environment (Dehghani Sanji et al. 2003). The objectives of this study were to (1) assess the performance of simpler models that require less readily available data against FAO56PM, and (2) to determine models performance across spaces in Jordan, focusing on arid versus semiarid environment. Evaluation of evapotranspiration models for estimating daily reference evapotranspiration in arid and semiarid environments O.E. MohaweshDepartment of Plant Production, Faculty of Agriculture, Mu'tah University, Al-Karak, Jordan ABSTRACT Daily outputs from eight evapotranspiration models were tested against reference evapotranspiration (ET o ) data computed by FAO56PM to assess the accuracy of each model in estimating ET o . Models were compared at eight stations across Jordan. Results show that Hargreaves modified models were the best in light of mean biased error (MBE), root mean square error (RMSE) and mean absolute error (MAE). The MBE, RMSE, and MAE values ranged from -1.47 to 0.81, 3.87 to 1.14 and 0.87 to 3.15 mm/day for HarM1, and from -1.45 to 0.89, 1.08 to 3.91, and 0.85 to 3.16 mm/day for HarM2, respectively, which would make it th...

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Estimation of leaf water potential by thermal imagery and spatial analysis*

Cited by 327 publications

References 16 publications

Evaluation of Source Leaf Responses to Water-Deficit Stresses in Cotton Using a Novel Stress Bioassay

Evaluation of Source Leaf Responses to Water-Deficit Stresses in Cotton Using a Novel Stress Bioassay

Estimation of Energy Balance Components over a Drip-Irrigated Olive Orchard Using Thermal and Multispectral Cameras Placed on a Helicopter-Based Unmanned Aerial Vehicle (UAV)

Evaluation of evapotranspiration models for estimating daily reference evapotranspiration in arid and semiarid environments

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