Relationship between photosynthetic radiation‐use efficiency of barley canopies and the photochemical reflectance index (PRI)

Abstract

Some processes of excess radiation dissipation have been associated with changes in leaf reflectance near 531 nm. We aimed to study the relations between the photochemical reflectance index (PRI) derived from this signal, and photosynthetic radiation‐use efficiency (defined as net CO2 assimilation rate/incident photon flux density) in a cereal canopy. Measurements of reflectance, fluorescence, gas exchange and xanthophyll cycle pigments were made in the morning, midday and afternoon in barley canopies with two levels of nitrogen fertilization. The photosynthetic radiation‐use efficiency decreased at midday, mainly in the third leaf, in both treatments, with lower values for the nitrogen deficient leaves. The zeaxanthin content showed the inverse pattern, increasing at midday and in the nitrogen deficient treatment. The photosynthetic radiation‐use efficiency was well correlated with the epoxidation state, EPS (violaxanthin + 0.5 antheraxanthin)/(violaxanthin + antheraxanthin + zeaxanthin). The PRI [here defined as (R539 ‐ R570)/(R539+ R570)] was significantly correlated with epoxidation state and zeaxanthin and with photosynthetic radiation‐use efficiency. These results validate the utility of PRI in the assessment of radiation‐use efficiency at canopy level.

Retrieval of the photochemical reflectance index for assessing xanthophyll cycle activity: a comparison of near-surface optical sensors

“…10), and indicate leaf responses are also detectable on a canopy scale with both instruments. These results are similar to previous diurnal studies by Gamon et al (1992) and Filella et al (1996).…”

“…Gamon et al, 1990Gamon et al, , 1992Gamon et al, , 2001Filella et al, 1996;Gamon and Berry, 2012). Significant correlations were observed between diurnal changes in EPS and PRI at both the canopy level and leaf level (Fig.…”

“…Gamon et al, 1992;Filella et al, 1996). Anomalously high canopy PRI values were noted in the early morning when SZAs exceeded ∼ 60 • , although the reasons for such values are likely to be instrumental and a combination of a low signal-to-noise ratio under low light conditions and the departure of the white reference panel and SKR 1800 cosine diffuser from true cosine behaviour at high SZAs (e.g.…”

Connection of the Photochemical Reflectance Index (PRI) with the Photosystem II Quantum Yield and Nonphotochemical Quenching Can Be Dependent on Variations of Photosynthetic Parameters among Investigated Plants: A Meta-Analysis

“…Connections between PRI and other photosynthetic parameters, including a quantum yield of photosystem II (∆F/F m ') [38,41,42,[45][46][47][48][49], photosynthetic light use efficiency (LUE) [3,48,[50][51][52][53][54][55], and net CO 2 uptake [47,[56][57][58][59], are actively being investigated. However, the results of these different works vary considerably, e.g., the linear correlation coefficients between PRI and NPQ can range from −0.90 [38,49,60] to +0.86 [41] in different investigations.…”

Dependence of spectral characteristics on parameters describing CO2 exchange between crop species and the atmosphere

“…This is probably connected with the fact that, apart from the contents of carotenoid pigments and light use efficiency, it is also influenced by several other factors, such as reflection from the soil background (as stated above -a highly significant factor in the case of the crops analysed in this study); proportions between direct and diffuse incoming radiation; structure of the canopy; the angle of solar rays; and sun-vegetation cover-sensor geometry (relative to the Sun as well as elements of the vegetation cover) (Grace et al, 2007;Hall et al, 2008;Louis et al, 2005;Suarez et al, 2008). Due to the measurement errors caused by these factors, although PRI works very well as an indicator of LUE at the leaf level (Filela et al, 1996;Gamon and Surfus, 1999;Penuelas et al, 1995Penuelas et al, , 1997, the accuracy of models based on this index is more limited if they are applied at the canopy level. Saturation of spectral data at high values of biophysical parameters estimated by them is a phenomenon that has frequently been observed in studies concerning the interdependencies of various parameters of the vegetation cover (Brantley et al, 2011;Tang et al, 2005;Wang et al, 2004;Zarco-Tejada 2005).…”