J. Penuelas et al., PHOTOCHEMICAL REFLECTANCE INDEX AND LEAF PHOTOSYNTHETIC RADIATION-USE-EFFICIENCY ASSESSMENT IN MEDITERRANEAN TREES, International journal of remote sensing, 18(13), 1997, pp. 2863-2868
This Letter presents new data validating the use of the photochemical
reflectance index PRI (R570-R531)/(R570+R531) to assess photosynthetic
-radiation-use-efficiency under mild water stress. Gas exchange, fluor
escence and the PRI of leaves from the Mediterranean trees Quercus ile
x and Phillyrea latifolia growing in the field were followed from spri
ng to summer 1996 in central Catalonia (NE Spain). The same variables
were measured in seedlings of these two species and Pistacia lentiscus
submitted to progressive drying after witholding irrigation. Except f
or severely drought damaged plants, significant relations of the refle
ctance index PRI with fluorescence yield of the photosystem II (Delta
F/F'(m)), nonphotochemical fluorescence quenching (qN) and photosynthe
tic radiation use efficiency (PRUE) were found, thus indicating a func
tional relation among these parameters. A simple portable radiometer m
easuring ground level reflectance at narrow bands centred at 531 and 5
70 nm could instantaneously calculate the PRI index and give the PRUE
estimation.