The hypothesis that heterosis in biomass production of sorghum (Sorghum bicolor L. Moench) may be ascribed to stability in carbon exchange rate (CER) over a wide range of environmental conditions was ...evaluated. This hypothesis was based on previous results from detached leaves that hybrids sustained greater CER over a wider temperture range than their parents. Two grain sorghum hybrids (AT×378/RT×430 and AT×378/RT×434) and their parental lines were grown in the greenhouse in a gradient of ambient temperatures under two water regimes (well-irrigated and drought up to heading). Plant water-use (estimated by weighing pots), leaf area, leaf gas exchange, grain yield, and above-ground biomass were determined. Significant heterosis was found for biomass, grain yield per plant, and grain number per panicle. No heterosis occurred for harvest index, indicating that heterosis in grain yield was due to heterosis in biomass. Neither growth duration nor leaf area could explain heterosis in biomass. CER and stomatal conductance for hybrid AT×378/RT×430 in the controls were greater than for both its parents at leaf temperatures above 38 °C. This, however, was not observed in the other hybrid which was less heterotic for biomass and grain yield in the controls. When CER data were subjected to a stability analysis by joint linear regression, the two hybrids had greater CER than their respective parents especially under conditions favouring high CER. When extreme stress conditions developed, the hybrid's performance depended on its genetic background more than on heterosis.
Field Spectroscopy of Agricultural Crops Bauer, Marvin E.; Daughtry, Craig S. T.; Biehl, Larry L. ...
IEEE transactions on geoscience and remote sensing,
1986-Jan., 1986-01-01, 1986, 1986-01-00, 19860101, Volume:
GE-24, Issue:
1
Journal Article
Peer reviewed
The design, implementation, and results of multisite multiyear experiments to measure and model the multispectral reflectance of agricultural crops in relation to their biophysical characteristics ...are described. The experimental approach involved multitemporal reflectance measurements together with detailed measurements of the agronomic characteristics of crop canopies. One result of the field measurements and analyses was a quantitative description of the complex relationships among crop canopy, soil, atmosphere, and illumination and sensor geometries. Leaf area index was identified as a key biophysical parameter linking crop physiology and multispectral remote sensing. Quantitative understanding and models of this relationship led to the development of spectral-temporal profile models for crop species identification and development stage estimation. A second key development has been the development of conceptual approaches and models for spectral estimation of leaf area index and light interception of crop canopies as inputs to crop growth and yield models. Other results include quantification of the effects of soil background, cultural practices, moisture stress, and nutrient deficiencies on crop reflectance, and the effects of sun angle and sensor view angle on measured canopy reflectance. The field measurements of canopy reflectance and geometry also provided data bases to test and validate canopy radiation models. In summary, the AgRISTARS field research on agricultural crops has provided a critical link between satellite and leaf spectral data.
Computer pattern recognition techniques were used to discriminate soil information from the Landsat Thematic Mapper (TM) and the French Systeme Probatoire d'Observation de le Terre (SPOT) satellite ...data on a native prairie near Manhattan, KS. Digital Elevation Model (DEM) data were merged to Landsat TM and SPOT data to delineate soil mapping units within the study area. Soil mapping units from a conventional soil survey were compared with a classified soil spectral map obtained from Landsat TM or SPOT, and DEM derived elevation, slope, and aspect data, using an overall accuracy assessment. The overall accuracy of soil spectral classes from TM and SPOT data was improved after DEM data were merged. A higher average accuracy for soil mapping units was obtained with a low frequency filtering transformation of the data. For Landsat TM data, Band 5 (middle infrared, 1.55-1.75 micrometers) was most useful for soil information extraction, and a higher overall accuracy was obtained in the dormant season compared with the accuracy in the growing season. The overall accuracy (about 57%) from SPOT data was slightly higher than the accuracy (about 53%) from Landsat TM at a similar wavelength range. Our results indicate that high resolution Landsat TM and SPOT satellite data can be used to aid second-order soil surveys in areas where the dominant land use is rangeland
Spectral indices have been used to predict leaf area index (LAI) and the interception efficiency of photosynthetically active radiation (PAR) within a plant canopy. The objectives of this work were ...to investigate the influence of canopy geometry on the temporal trends in LAI and spectral indices, and to develop equations to predict the daily canopy gross carbon dioxide exchange rates (DGCE) from daily PAR. Winter wheat (Triticum aestivum L. cv. Newton) was planted in north-south and east-west row orientations with 0.18-, 0.35-, and 0.71-m row spacings, during 1982-1983 and 1983-1984. Net CO2 exchange rates were measured with a transparent dynamic positive-pressure chamber and a differential infrared gas analysis system. Daytime dark respiration rate correction were made to obtain the DGCE. Canopy spectral reflectance was monitored with a multispectral radiometer, while absorption of PAR was measured with quantum sensors. Daily absorbed PAR was derived by taking the product of interception efficiency estimated from either the LAI or spectral indices, and total incoming PAR. Row orientation did not significantly influence the temporal trends in LAI or the spectral response, whereas significantly greater LAI and spectral response occurred in the narrower- vs. wider-spaced canopies. A linear model characterized the relationship between DGCE and daily absorption of PAR. A common slope model (0.74 g CO2 mol-1 photon) indicated that the LAI and spectral indices had similar predictive capabilities. Good agreement occurred between an equation developed with 1984 data and measured values from 1983 (i.e., R2 0.49-0.65). Remotely sensed multispectral canopy reflectance data, therefore, can be used to estimate DGCE in wheat canopies
Drought stress frequently limits soybean production. Thirty soybean Glycine max (L.) Merr. lines in a field trial in 1982 were tested for canopy temperatures and response to vapor pressure deficit ...(VPD) as criteria for yield and drought tolerance. Lines were monitored for canopy temperature differential seasonal mean = canopy temperature -- air temperature), and wet and dry bulb temperatures determined the VPD of the air. The five warmest and five coolest lines based on seasonal mean were monitored for seasonal mean in 1983 and 1984 under irrigated and nonirrigated environments. Soil type was (Umucic Hapiustoll) a Muir silt loam (fine-silty, mixed, mesic in 1982 and 1984) and a Eudora silt loam soil (coarse-silty, mixed, mesic Fluventic Hapludoll) in 1983. Differences for seasonal mean among the lines were negatively correlated with seed yield. Warm genotypes were not nore productive under dryland conditions, nor was the ratio of dryland yield to irrigated yield (yield stability) greater than for cool genotypes. Neither seasonal mean nor the ratio of dryland seasonal mean to irrigated seasonal mean (Td stability) was significantly correlated with yield stability. Lines did not differ significantly in their seasonal mean response to VPD (measured as the seasonal mean - VPD regression slope) on a seasonal basis. On 5 d with maximum VPD greater than 3 kPa, however, seasonal mean response to VPD differed significantly in the irrigated environment. These differences were not related to seasonal mean, yield, or yield stability. Indirect selection for yield using canopy temperature may be effective; however, warm genotypes are not more drought tolerant or yield stable than cooler selection
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