Filella I, Serrano L, Serra J, Peñuelas J (1995) Evaluating wheat nitrogen status with canopy reflectance indices and discriminant analysis. Crop Science 35:1400-1405.
Peñuelas J, Filella I, Gamon JA (1995) Assessment of photosynthetic radiation-use efficiency with spectral reflectance. New Phytologist 131:291-296.
Peñuelas J, Baret F, Filella I (1995) Semi-empirical indices to assess carotenoids/Chlorophyll a ratio from leaf spectral reflectance. Photosynthetica 31:221-230.
Peñuelas J, Filella I, Gimeno B (1995) La fitotoxicitat de l'ozó troposfèric a Catalunya avaluada amb plantes de tabac biosensores. Butlletí de la Institució Catalana d'Història Natural 63:133-140.
Peñuelas J., Filella I. (1995) Reflectance assessment of mite effects on apple trees. International Journal of Remote Sensing. 16: 2727-2733.EnlaceDoi: 10.1080/01431169508954588
Reflectance measurements were conducted in field plots of Golden Smoothee 2038 apple cultivar subjected to different levels of mite attack (from 0 to 500 cumulative mite days) over a 2-year period. Chlorophyll concentration decreased and carotenoid/chlorophyll a ratio increased with increasing level of attack. Classical reflectance indices such as red edge wavelength or the Normalized Difference Vegetation Index were unable to distinguish among treatments. On the other hand, spectral indices based on carotenoid/chlorophyll a (SRPI R430/R680) and chlorophyll degradation (Normalized Phaeophytinization Index calculated as (R415-R435)/(R435 +R415)) were correlated with the level of attack. These reflectance indices show potential uses of visible reflectance as non-invasive, non-destructive techniques for detection of mite effects. © 1995 Taylor & Francis Ltd.
Peñuelas J., Filella I., Elvira S., Inclán R. (1995) Reflectance assessment of summer ozone fumigated Mediterranean white pine seedlings. Environmental and Experimental Botany. 35: 299-307.EnlaceDoi: 10.1016/0098-8472(95)00019-0
Seedlings of Pinus halepensis L. grown for three summers in open top chambers (OTC) in Northeastern Spain were exposed to three ozone (O3) treatments: charcoal filtered air (CA), non-filtered (NF) and non-filtered plus 40 nl 1-1 O3 (FU). Ambient air plots (AA) in open air were established to assess the chamber effect. A clear seasonal trend was found in the physiological response of these pine seedlings in summer periods, with lower needle chlorophyll concentrations, and higher absorbance ratios for wavelengths at 435 nm and 665 nm ( A435 A665) which is indicative of carotenoid/chlorophyll a ratio. Old needles from the FU treatment had lower chlorophyll content and higher absorbance ratios ( A435 A665) than those of other treatments. Spectral reflectance indices assessing green biomass (NDVI), chlorophyll concentration ('red edge'), the carotenoid/chlorophyll ratio (SIPI), and photosynthetic efficiency (SIXI) clearly followed the same seasonal trend, but were not statistically distinguishable from those of different ozone levels. These results are attributable to the dominance by the young needles in the sensor's field of view, which showed no clear biological differences with ozone treatment. Only ambient air seedlings presented different values for the reflectance indices in consonance with their lower chlorophyll content and higher carotenoid/chlorophyll ratio. © 1995.
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