c7.6.9 – Does photochemical reflectance index provide reliable estimates of photosynthetic activity under water stress conditions in evergreen and deciduous tree species?

Ripullone F* (1), Rivelli A (1), Magnani F (2), Raddi S (3), Guerrieri M (1), Baraldi R (4), Gentilesca T (1), Guarini R (1), Nolè A (1), Borghetti M (1)

(1) DiSCOFA, Università della Basilicata, Potenza; (2) Dipartimento Colture Arboree, Università di Bologna; (3) DiSTAF, Università di Firenze; (4) Istituto di Biometereologia, CNR, Bologna
Collocazione: c7.6.9 – Tipo Comunicazione: Presentazione orale
7° Congresso SISEF *
Sessione 6: “Ecosistemi forestali e fattori ambientali” *

Contatto: Francesco Ripullone (francesco.ripullone@unibas.it)

Abstract: Although in recent years the photochemical reflectance index (PRI) demonstrated to be a promising tool to monitor the photosynthetic activity or light-use efficiency of vegetation, it showed much less reliable under drought conditions because of likely alteration of the reflectance signal occurring under severe water stress. However, these previous studies have been mainly carried out on herbaceous and shrubland species, while it lacks information on tree species of forest ecosystems; this may in fact limit the application of PRI on Mediterranean regions that are subjected to frequent and severe water stress. In this study, we tested the reliability of PRI to estimate plant water stress and maximum photosynthetic capacity at saturating light (Amax) in seedlings of forest species submitted to progressive drying after withholding irrigation. To this aim, eight forest species bred in a nursery have been selected among the most diffusive evergreen and deciduous species in Mediterranean area to cover a wide range of photosynthetic potential, vegetation types and drought sensitivity. Our results indicate that PRI is a reliable indicator of plant water stress, overall in species less sensitive to drought i.e., evergreen species. By contrast, other indexes such as water index (WI) and normalised difference vegetation index (NDVI) appeared to be less reliable. PRI showed also to be well correlated with light-use efficiency (estimated from modulated fluorescence as DF/F’m) and photosynthetic activity variations (as estimated by Amax) for almost all species. Furthermore, the good correlation observed between xanthophyll depoxidation state (DEPS) and PRI, confirms a strong involvement of xanthophylls pigments in PRI changes under severe drought. It is concluded that, contrary to early reports, PRI showed to be reliable in monitoring photosynthetic dynamic changes even under severe water stress encouraging the use of this index for future remote sensing applications.

Citazione: Ripullone F , Rivelli A , Magnani F , Raddi S , Guerrieri M , Baraldi R , Gentilesca T , Guarini R , Nolè A , Borghetti M (2009). Does photochemical reflectance index provide reliable estimates of photosynthetic activity under water stress conditions in evergreen and deciduous tree species? . 7° Congresso Nazionale SISEF, Isernia – Pesche (IS), 29 Set – 03 Ott 2009, Contributo no. #c7.6.9