Preliminary Assessment of the Relationship between Pigments in Olive Leaves and Vegetation Indices

Content of leaf pigments such as chlorophyll a and b, chlorophyll a+b and carotenoids can provide valuable insight into the physiological performance of plants. These compounds have selective proprieties for light absorption and reflectance in the visible spectra that can be used to evaluate alternative methods to biochemical to estimate their content. Numerous studies in the literature have established correlations between these compounds, spectral reflectance and vegetation indices. Nevertheless, the appropriate use of these indices depends on plant species and cultivars. Thus, the objective of this study was to assess the most common vegetation indices for the estimation of chlorophyll a and b, chlorophyll a+b and carotenoids of three olive tree cultivars (Olea europaea L, cv. Cobrançosa, cv. Verdeal Transmontana and cv. Madural) under six irrigation treatments, using spectroscopy. The results showed that the correlation between leaf pigments and vegetation indices depends not only on the type of pigment but also on the cultivar. Among the studied cultivars, cv. Cobrançosa showed the best correlation between the “M Locherer chlorophyll” index (MLO) and chlorophyll a content (r2 = 0.66) and for the carotenoid reflectance index (CRI) 2 and carotenoids content (r2 = 0.87). Although the results are preliminary, it seems that vegetation indices could be a useful tool for leaf pigment evaluation, and to give information about plant interactions with biotic and abiotic environmental stress conditions.