Leaf dorsoventrality as a paramount factor determining spectral performance in field-grown wheat under contrasting water regimes.

Omar Vergara-Díaz,Fadia Chairi,Maria Teresa Nieto-Taladriz,José Luis Araus,Shawn C Kefauver,Nieves Aparicio,Rubén Vicente,Jose A Fernandez-Gallego

doi:10.1093/jxb/ery109

Abstract

The effects of leaf dorsoventrality and its interaction with environmentally induced changes in the leaf spectral response are still poorly understood, particularly for isobilateral leaves. We investigated the spectral performance of 24 genotypes of field-grown durum wheat at two locations under both rainfed and irrigated conditions. Flag leaf reflectance spectra in the VIS-NIR-SWIR (visible-near-infrared-short-wave infrared) regions were recorded in the adaxial and abaxial leaf sides and at the canopy level, while traits providing information on water status and grain yield were evaluated. Moreover, leaf anatomical parameters were measured in a subset of five genotypes. The spectral traits studied were more affected by the leaf side than by the water regime. Leaf dorsoventral differences suggested higher accessory pigment content in the abaxial leaf side, while water regime differences were related to increased chlorophyll, nitrogen, and water contents in the leaves in the irrigated treatment. These variations were associated with anatomical changes. Additionally, leaf dorsoventral differences were less in the rainfed treatment, suggesting the existence of leaf-side-specific responses at the anatomical and biochemical level. Finally, the accuracy in yield prediction was enhanced when abaxial leaf spectra were employed. We concluded that the importance of dorsoventrality in spectral traits is paramount, even in isobilateral leaves.

Highlights

Spectroradiometry is a pivotal technique in the remote sensing evaluation of plant performance, used widely for precision agriculture, high-throughput phenotyping, and ecosystem studies
We investigated the spectral performance of 24 genotypes of field-grown durum wheat at two locations under both rainfed and irrigated conditions
Leaf dorsoventral differences suggested higher accessory pigment content in the abaxial leaf side, while water regime differences were related to increased chlorophyll, nitrogen, and water contents in the leaves in the irrigated treatment

Summary

Introduction

Spectroradiometry is a pivotal technique in the remote sensing evaluation of plant performance, used widely for precision agriculture, high-throughput phenotyping, and ecosystem studies. Very diverse information is retrieved from the spectral signature of the light reflected by the canopy or even by single leaves (Ustin et al, 2009), and to date a large corpus of spectral reflectance indices has been formulated (Xue and Su, 2017) This information is usually predicted in an empirical manner without a clear understanding of how a basic aspect such as leaf side (adaxial versus abaxial) may affect the spectrum of the reflected radiation and the different categories of spectroradiometrical indices. Changes in morphology, anatomy, turgor status, and biochemical content can directly and/or indirectly impact the reflected radiation This is the basis for plant status studies using a spectroscopic approach. Few studies have considered leaf-side-specific responses, and those focusing on the leaf dorsoventral effect have usually been performed on plant species with a clear bifacial leaf anatomy (Evans, 1999; Lu et al, 2015)

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