Peñuelas J., Filella I. (1995) Reflectance assessment of mite effects on apple trees. International Journal of Remote Sensing. 16: 2727-2733.EnllaçDoi: 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.EnllaçDoi: 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.
Estiarte M., Peñuelas J., Kimball B.A., Idso S.B., Lamorte R.L., Pinter P.J., Wall G.W., Garcia R.L. (1994) Elevated CO2 effects on stomatal density of wheat and sour orange trees. Journal of Experimental Botany. 45: 1665-1668.EnllaçDoi: 10.1093/jxb/45.11.1665
No significant differences were found in stomatal densities or stomatal indices of wheat or sour orange trees grown at high CO2 concentrations in two different CO2 enrichment systems (Free-Air CO2 Enrichment for wheat and Open-Top Chambers for orange trees). These results are in accordance with most of the previous results obtained in short-term experimental studies which suggest that plants do not acclimate to increasing CO2 concentration by changing stomatal density within a single generation. © 1994 Oxford University Press.
Filella I, Peñuelas J (1994) The red edge position and shape as indicators of plant chlorophyll content and biomass. International Journal of Remote Sensing 15:1459-1470.
Peñuelas J, Ribas M, González M, Azcón-Bieto J (1994) Respiration responses in ozone fumigated spruces. Environmental and Experimental Botany 34:443-449.
Field, CB, Gamon JA, Peñuelas J (1994) Remote sensing of photosynthesis. In Schulze ED, Caldwell MM (eds) Ecophysiology of photosynthesis. Springer, pp. 511-527.
Peñuelas J, Matamala R (1994) Elemental composition of beans and peppers under nitrogen and water-stress. Plant Physiology (Life Science Advances) 13:273-278.
Peñuelas J, Gamon J, Freeden A, Merino J, Field C (1994) Reflectance indices associated with physiological changes in nitrogen- and water-limited sunflower leaves. Remote Sensing of Environment 48:135-146.
Duarte CM, Planas D, Peñuelas J (1994) Macrophytes, taking control of an ancestral home. In Margalef R (ed) Limnology. Elsevier, pp 59-79.
Peñuelas J (1994) Why terrestrial vegetation tends to have a leaf area index of 4? Spectrum 18:74-75.
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