Hailstorm effects on leaf area index (LAI) and chlorophyll, anthocyanin, and flavonoid pigments in winter wheat (Triticum aestivum L.)

Hailstorms may seriously harm crops, resulting in yield losses and eventually worsening the financial situation of farmers. The crop's growth stage at which damage occurs may have an influence on the yield damage degree as well. Hail damages can result in stem breakings that prevent nutrients from moving towards the spikes in winter wheat (Triticum aestivum L.), as well as defoliation and direct grain loss, thus reducing the final yield output. Defoliation, may results in detectable leaf area index decreases, as well as plant pigment changes caused by the injuries. Considering the spatial and intensity extent that these weather events can reach, and the difficulties of precise on-site damage assessment by insurance field inspectors, there is a need to find suitable vegetation traits that can help to better define damage for remote sensing upscaling. During the 2022 cropping season, this study was conducted at the University of Padova’s experimental farm “L. Toniolo” in Legnaro (Northern Italy), to explore the effects of hailstorms on the leaf area index, chlorophyll content, anthocyanins, and flavonoids on winter wheat at different developmental stages (flowering, milky and over-ripe). Four damage intensities (0%, 20%, 50%, and 80%) were simulated in three replicates during different plant developmental stages using specifically built prototypes. The study compared two techniques for calculating LAI: destructive and non-destructive, considering the crucial significance of LAI as a proxy measure for vegetation state and modeling. The utility and dependability of the indirect measurements made with a ceptometer (non-destructive) were confirmed by the generally good agreement with the direct (destructive) LAI measurements. The crop was then monitored across the May-July span of the cropping season. When wheat was severely damaged by hail, there was a general decrease in LAI and chlorophyll content following damage. The latter, though, showed a distinct behavior at the end of the season, with increase chlorophyll concentration in the most damaged plants. Anthocyanins and flavonoids generally increased following damage across all plant stages. The yield damage degree was mostly influenced by the damage intensity, with the 80% treatment resulting in an average yield drop of 55% in comparison to the control across all the considered stages.