HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Campbell, P. K. E. Articles by Chappelle, E. W. Search for Related Content PubMed PubMed Citation Articles by Campbell, P. K. E. Articles by Chappelle, E. W. Agricola Articles by Campbell, P. K. E. Articles by Chappelle, E. W. Related Collections Soybean Maize Plant Analysis Plant and Environment Interactions

Assessment of Vegetation Stress Using Reflectance or Fluorescence Measurements

^a Joint Center for Earth Systems Technology, Univ. of Maryland, Baltimore County (UMBC), Baltimore, MD 20771, USA
^b (current address), Biospheric Sciences Branch, Code 614.4, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 USA
^c Biospheric Sciences Branch, Code 614.4, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 USA
^d Hydrology and Remote Sensing Lab., Agricultural Research Service, USDA, Beltsville, MD 20705 USA
^e Science Systems and Applications Inc. (SSAI), Lanham, MD 20706 USA

View larger version (33K): [in this window] [in a new window]   Fig. 1. (A) Typical fluorescence (F) emissions (400–800 nm) for the three species in this study, including corn (black, bold), soybean (gray), and maple (black). F (counts/second [c/s]) were produced using a 360-nm excitation wavelength, exhibiting distinct F features in the blue, green, red, and far-red regions. (B) F emissions from the three species significantly differed in the blue and green regions (F440 and F530, adaxial leaf surface): corn (black circles); soybean, Ks4694 (gray + symbols); soybean, Manokin (gray x symbols); and maple (black triangles).

View larger version (26K): [in this window] [in a new window]   Fig. 2. The changes in spectral fluorescence and reflectance are shown for corn leaves (Experiment I) that were provided in eight N applications rates between 0 and 150% of the optimal (100%) levels (n = 16 per group). Differences among treatments were highly significant for the two spectral regions in the green and red/far-red (Regions 1 and 2; delineated as dotted rectangles): (A) fluorescence emissions (400–800 nm); (B) reflectance (400–800 nm); and (C) the first derivative of the red-edge reflectance spectra, between 675 and 775 nm. Similar responses were observed across all three experiments.

View larger version (35K): [in this window] [in a new window]   Fig. 3. Fluorescence and reflectance for the experimental treatment groups, shown in each panel for the three experiments, left to right: Exp. 1, Exp II (Manokin, KS4694), and Exp. III. The means and SE are shown for each group for four spectral variables: (A) F530/F740 (top panel); (B) D715/D705 (second panel); (B) Av...R (615...725) (third panel); and (B) TM3/TM1 (bottom panel).

View larger version (17K): [in this window] [in a new window]   Fig. 4. Reflectance of adaxial vs. abaxial leaf surfaces for the three species are shown: (A) R500; and (B) R720. Species symbols: corn (black circles); soybean, Ks4694 (+ symbols); soybean, Manokin (x symbols); and maple (black triangles).

View larger version (30K): [in this window] [in a new window]   Fig. 5. The correlation of total chlorophyll across the VIS/NIR near-infrared spectrum (400–800 nm) to the mean fluorescence (gray line) and reflectance (black line) spectra for the abaxial surface of soybean leaves (Manokin var.).

View larger version (23K): [in this window] [in a new window]   Fig. 6. The trends of N application levels for a corn crop are compared for two of the most successful spectral indices: F530/F740 (solid gray line) and REIPw (broken black line). The F ratio detects the 100% group as the minimum F530/F740 value.