Reflectance and biochemical responses of maize plants to drought and re‐watering cycles

Abstract

The ability to recover from drought stress after re-watering is an important feature that will enable plants to cope with the predicted increase in episodic drought. The effects of pre-drought and re-watering conditions on leaf spectral properties and their relationships with the biochemical processes that underlie the recovery from pre-drought conditions should be better understood. The reflectance spectra, 10 spectral reflectance indices (SRIs) and biochemical characteristics of maize (Zea mays) leaves were monitored 7, 14, 21 and 28 days after the initiation of soil drought stress during two successive cycles of drought and re-watering periods. The leaf reflectance of the two inbred maize lines increased under the drought stress, especially in the visible spectral range. In addition, an obvious recovery of the leaf reflectance was only observed in the first re-watering period, and its value remained higher than that of the control plants during the second recovery period. A recovery lag in the pigment contents was also observed during the second cycle. The recovery variations in the pattern and magnitude of the SRIs and the total contents of C, N and P that were measured in response to the re-watering during both cycles were diverse and complex; both full and partial recoveries were observed. The SRIs representing different physiological attributes of plant growth, including the water index, red edge position, photochemical reflectance index and near-infrared reflectance at 800 nm, showed strong linear relationships (P < 0.01 or 0.05) with the growth and biochemical traits across the successive drought and re-watering cycles. The results suggest that maize plants can adjust their leaf reflectance properties and employ growth and biochemical strategies to adapt to cyclic drought stress and recover from drought stress after re-watering.

Proximal Hyperspectral Imaging Detects Diurnal and Drought-Induced Changes in Maize Physiology

“…The earliest effects were observed in the visible region, where an increase in red reflectance was present two days after the onset of the drought treatment. Increases in red reflectance attributed to changes in pigment content ( Sims and Gamon, 2002 ; Sun et al, 2018 ) were not visible here, instead red reflectance showed a strong correlation with photosynthetic efficiency (Φ PS 2 or F v ′/F m ′) and Ψ, suggesting that other factors, such as light scattering within the leaf and chloroplast positioning, may have impacted red reflectance during the drought treatment. The negative relationship between red reflectance and Ψ did not differ between treatments, implying that the underlying link is the same for developmental and drought-induced changes.…”

“…A vast number of indices created for remote sensing applications are now used in proximal phenotyping studies. NDVI is a very popular index applied in several drought studies ( Kim et al, 2011 ; Römer et al, 2012 ; Behmann et al, 2014 ; Sun et al, 2018 ). Its performance ranges from no drought-induced differences to a significant reduction in NDVI values.…”

“…This was confirmed here, because the NDVI only showed significant effects from day 4 of the drought treatment onwards, while the RGRI detected effects by the second day. In maize, drought treatments cause an increase in RGRI values ( Sun et al, 2018 ), which can be attributed to changes in photosynthetic efficiency and/or pigment content. Because a mild drought was applied during these experiments, no clear differences in pigment content were observed, while photosynthetic efficiency (F v ′/F m ′ and Φ ps2 ) was significantly reduced and strongly correlated with the RGRI ( Figure 5 ).…”

Canopy spectral reflectance indices correlate with yield traits variability in bread wheat genotypes under drought stress

“…This wavelength is often used to measure the pigment concentration in the canopy, the senescence pattern, photosynthetic activity, biomass accumulation, leaf area, the yield of grains, and plant hydration status ( El-Hendawy et al, 2015 ; Gizaw, Garland-Campbell & Carter, 2016 ; Prasad et al, 2009 , 2007 ; Sun et al, 2019 ). Ground-based proximate sensing is a simple, rapid, practical, and cost-effective method for determining the spectral reflectance of the canopy and has been effectively utilized to evaluate a variety of phenotyping features associated with drought resistance ( El-Hendawy et al, 2015 ; Gizaw, Garland-Campbell & Carter, 2016 ; Sun et al, 2018 ; Zhou et al, 2022 ).…”

Photosynthetic resistance and resilience under drought and rewatering in maize plants

“…A recent report showed that a watering treatment following a drought can lead to a greater recovery of some key functional traits in plants (Harrison et al, 2018). For example, both full and partial recoveries of leaf pigment and nitrogen contents were observed in drought-stressed maize plants following rewatering (Sun et al, 2018). Drought has been an important factor in the growth of maize, the most widely grown crop in the world.…”