Assessing the Potential of Downscaled Far Red Solar-Induced Chlorophyll Fluorescence from the Canopy to Leaf Level for Drought Monitoring in Winter Wheat

Abstract

Solar-induced chlorophyll fluorescence (SIF) from ground, airborne, and satellite-based observations has been increasingly used in drought monitoring recently due to its close relationship with photosynthesis. SIF emissions respond rapidly to droughts, relative to the widely used vegetation indices (VIs), thus indicating their potential for early drought monitoring. The response of SIF to droughts can be attributed to the confounding effects of both the physiology and canopy structure. In order to reduce the reabsorption and scattering effects, the total emitted SIF (SIFtot) was proposed and served as a better tool to estimate GPP compared with the top-of-canopy SIF (SIFtoc). However, the response time and response magnitude of SIFtot to droughts and its relationships with the environmental parameters and soil moisture (SM) (i.e., the knowledge of drought monitoring using SIFtot) remains unclear. Here, the continuous ground data of F760toc (SIFtoc at 760 nm) from a nadir view that was downscaled to F760tot (SIFtot at 760 nm), NIRv, and the NDVI, SM, meteorological, and crop growth parameters were measured from four winter wheat plots with different intensities of drought (well-watered, moderate drought, severe drought, and extreme drought) over 2 months. The results indicated that F760tot was more closely correlated with the SM than the VIs at short time lags but weaker at longer time lags. The daily mean values of F760tot and NIRv were able to distinguish the differences between different drought levels, and F760tot responded quickly to the onset of drought, especially for the moderate drought intensity. These findings demonstrated that F760tot has potential for early drought monitoring and may contribute to mitigating the risk of agricultural drought.

Exploring Physiological and Nonphysiological Responses of Sun-Induced Chlorophyll Fluorescence to Different Levels of Water Stress in Winter Wheat

“…In addition, the total emitted SIF (SIFtot) was calculated as the result of dividing SIF by fesc, and hence SIFtot contained more physiological information compared with SIF. Our previous study [48] indicated that SIFtot responded quickly to the onset of water stress compared with SIF, especially for moderate water stress. This highlights the importance of ΦF to some extent, but it includes the influences of radiation and partial canopy structure (e.g., fPAR).…”

The Afternoon/Morning Ratio of Tower-Based Solar-Induced Chlorophyll Fluorescence Can Be Used to Monitor Drought in a Chinese Cork Oak Plantation

“…Vegetation indices (VIs), such as the normalized difference vegetation index (NDVI) and enhanced vegetation index (EVI), have been extensively employed for drought monitoring, capturing alterations in canopy structure and leaf optical properties (e.g., leaf area, pigment, dry ma er, and water) [9,10]. However, these indicators face limitations in monitoring short-term drought instances that do not induce substantial changes in canopy structure and leaf optical properties [8,11,12]. Additionally, these indices cannot efficiently detect rapid changes in instantaneous photosynthesis under drought conditions due to their limited sensitivity to photosynthesis [13,14].…”

Green Synthesis of Iron Oxide (Hematite) Nanoparticles and Their Influence on Sorghum bicolor Growth under Drought Stress

“…Drought is a major abiotic stress that affects plant growth and development, but its effects depend on the severity and duration of the stress and the plant species. Drought limits the absorption of water and nutrients in plants and affects plants’ metabolism, stomatal conductance, and photosynthetic rates, and these subsequently decrease growth and negatively impact crop yield [ 5 , 6 , 7 ]. Water deficit causes the accumulation of reactive oxygen species (ROS) such as superoxide radicals (O 2 ●− ), hydrogen peroxide (H 2 O 2 ), and hydroxyl radicals (OH), among others.…”