ESTIMATION OF STRAWBERRY LEAF CHLOROPHYLL CONTENT AND PHOTOSYNTHETIC ACTIVITY USING REFLECTANCE AND FLUORESCENCE MEASUREMENTS IN THE FIELD

Portable spectroscopy and fluorescence instruments were used to establish a nondestructive method for estimating chlorophyll (Chl) content and photosynthetic activity in strawberry leaves. 25 genotypes of Fragaria chiloensis were selected as experimental material from a large, replicated field collection. Gas exchange, Chl content, leaf reflectance spectra and induction kinetics of fluorescence from dark-adapted leaves were measured in newly expanded mature leaves. Negative correlation coefficients between reflectance measurements at 510-650 nm and 690-700 nm and Chl a, b and total Chl were highly significant and reached their peak values around 570 nm (r = -0.80**, total Chl). Multiple regression analysis showed that combining the reflectance measurements at 520 nm with 570 nm significantly improved the model's correlation coefficient (r = 0.86***, total Chl). Reflectance at 520 and 570 seems to represent signals from different components in the photosynthetic apparatus. Combining certain fluorescence parameters with reflectance measurements significantly improved the correlation with Chl a, b and total Chl (r = 0.91***, total Chl). The regression model combining reflectance and fluorescence measurements offers a useful, nondestructive method to simultaneously assess leaf Chl content and induction kinetics of fluorescence using portable spectroscopy and fluorescence instruments. Fluorescence parameters F v /F m and F t combined to show a moderate relationship (r = 0.66**) with CO 2 assimilation rate.