Potential of UAV-based sun-induced chlorophyll fluorescence to detect water stress in sugar beet

Na Wang*, Jan G.P.W. Clevers, Sebastian Wieneke, Harm Bartholomeus, Lammert Kooistra

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

1 Citation (Scopus)

Abstract

Sun-induced chlorophyll fluorescence (SIF) is a direct indicator of plant photosynthetic activities and can potentially indicate plant physiological changes caused by water stress. However, the direct effect of water stress on the physiological SIF responses in crops at the field level still needs further research to clearly understand the involved mechanisms. To study this relationship, we made use of Unmanned Aerial Vehicles (UAVs), which are flexible and cost-effective to acquire SIF data at a high temporal resolution. We acquired near-infrared SIF (760 nm) and red SIF (687 nm) measurements using a UAV platform over irrigated and non-irrigated sugar beet plots. To represent physiological changes in crops, we calculated the apparent SIF yield (SIF normalized by the absorbed photosynthetically active radiation) at 760 and 687 nm (SIF760yield and SIF687yield), the fluorescence emission yield at 760 nm (ΦF760), and the SIFratio (the ratio between SIF687 and SIF760). ΦF760 was estimated using the recently developed NIRvH approach. For an improved interpretation of the response of these SIF indicators, we also acquired additional UAV-based hyperspectral and thermal data. We found that on June 28, when sugar beets were experiencing water stress, SIF687yield, ΦF760, and SIFratio all showed a significant response to the recovery of the irrigated sugar beets (p-value < 0.05). On the other hand, on July 24 when both water stress and heat stress affected the crop, only ΦF760 and SIFratio weakly tracked the changes induced by the irrigation (p-value < 0.1). ΦF760 had similar changes to SIF760yield in both June and July, but ΦF760 was more sensitive to irrigation. This indicates the importance of correcting for the structural effect when interpreting the SIF response. The findings suggest that SIF indicators can indicate water stress at the field level, but its value to detect the changes of photosynthetic activities under severe stress needs more investigation.
Original languageEnglish
Article number109033
JournalAgricultural and Forest Meteorology
Volume323
DOIs
Publication statusPublished - 1 Aug 2022

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