RATIOS OF LEAF REFLECTANCES IN NARROW WAVEBANDS AS INDICATORS OF PLANT STRESS

Ratios of leaf reflectances that were measured within narrow wavebands (2 nm) were evaluated as indicators of plant stress. Wavebands used i n ratio computation were based on earlier studies that determined the wavelength regions in which reflectance was most affected by 8 stress agents among 6 plant species. Several ratios, such as reflectance at 6 95 nm divided by reflectance at 670 nm (R695/R670), were affected by s ome but not all stress agents. However, R695/R420, R605/R760, R695/R76 0 and R710/R760 were significantly greater (p less-than-or-equal-to 0. 05) in stressed compared with non-stressed leaves for all stress agent s. The ratios that most strongly indicated plant stress were reflectan ce at 695 nm divided by reflectance at 420 nm or 760 nm.