A New Perspective on Drought Monitoring: Application of Solar-Induced Chlorophyll Fluorescence (SIF) in Drought Stress Response

干旱是一種嚴(yán)重的環(huán)境壓力，會(huì)削弱植物的生長(zhǎng)和光合作用，進(jìn)而影響生態(tài)系統(tǒng)和糧食安全。有沒有一種工具能提前捕捉到植物缺水時(shí)的微妙變化，幫助及時(shí)監(jiān)測(cè)干旱狀況，減輕其影響呢？

答案是有的，這就是日光誘導(dǎo)葉綠素?zé)晒猓ê?jiǎn)稱SIF）?？梢孕蜗蟮卣f，SIF是植物釋放的光合作用信號(hào)，通過捕捉這束微弱的熒光，我們能實(shí)時(shí)感知作物的健康狀態(tài)和干旱脅迫響應(yīng)。

Drought is a severe environmental stress that impairs plant growth and photosynthesis, thereby affecting ecosystems and food security. Is there a tool that can detect subtle changes in plants during water deficits early, enabling timely drought monitoring and mitigation?

The answer lies in solar-induced chlorophyll fluorescence (SIF), a signal emitted by plants during photosynthesis. By capturing this faint fluorescence, we can monitor crop health and drought stress responses in real time.

簡(jiǎn)單說說SIF

我們之前的文章已經(jīng)詳細(xì)介紹過，SIF是在光合作用過程中，葉綠素被激發(fā)后釋放出的熒光信號(hào)。它能直接反映光合作用的活躍度，是監(jiān)測(cè)植物生理狀態(tài)的黃金指標(biāo)。

那么，怎么捕捉這種幾乎肉眼不可見的熒光呢？研究人員開發(fā)了多種技術(shù)手段，從地面光譜儀到高空遙感衛(wèi)星，都能測(cè)量SIF。傳統(tǒng)的衛(wèi)星雖然覆蓋廣，但空間和時(shí)間分辨率有限。愛博能推出了在線式和無人機(jī)載的日光誘導(dǎo)葉綠素?zé)晒?SIF)觀測(cè)系統(tǒng)，實(shí)現(xiàn)多尺度觀測(cè)，可直接獲得日光誘導(dǎo)葉綠素?zé)晒?、光合作用速率、歸一化植被指數(shù)、增強(qiáng)植被指數(shù)等參數(shù)。

To briefly explain SIF, it is the fluorescent signal released when chlorophyll molecules are excited during photosynthesis. Because SIF directly reflects photosynthetic activity, it serves as a valuable indicator for assessing plant physiological status.

How do we capture this nearly invisible fluorescence? Researchers have developed various technologies ranging from ground-based spectrometers to airborne and satellite remote sensing platforms capable of measuring SIF. Conventional satellites offer broad coverage but are limited in spatial and temporal resolution. The company EXPONENT (愛博能) has developed both online and drone-mounted SIF Monitoring systems that enable multi-scale monitoring and provide real-time measurements of SIF, photosynthetic rate, normalized vegetation index (NDVI), enhanced vegetation index (EVI), and other parameters.

愛博能SIF系列產(chǎn)品 / EXPONENT SIF Product Series

SIF如何幫我們監(jiān)測(cè)干旱？ / How does SIF help monitor drought?

研究人員為了認(rèn)識(shí)SIF與干旱脅迫之間的關(guān)系，可謂使出了渾身解數(shù)。其中，一個(gè)中國(guó)團(tuán)隊(duì)搭建了一個(gè)實(shí)驗(yàn)田和智能灌溉控制系統(tǒng)，結(jié)合地面實(shí)測(cè)與SIF觀測(cè)，來動(dòng)態(tài)監(jiān)控作物水分狀況。

他們讓冬小麥經(jīng)歷4種程度的干旱脅迫，實(shí)時(shí)采集SIF信號(hào)，同時(shí)監(jiān)測(cè)光合速率和其他生理指標(biāo)。結(jié)果發(fā)現(xiàn)，SIF與光合速率呈高度正相關(guān)。更重要的是，SIF對(duì)輕度干旱的響應(yīng)比傳統(tǒng)土壤水分測(cè)量更早更敏感，提前預(yù)警能力較強(qiáng)。這項(xiàng)研究不僅驗(yàn)證了SIF作為干旱監(jiān)測(cè)指標(biāo)的科學(xué)性，還為智能農(nóng)業(yè)灌溉提供了數(shù)據(jù)支持，具有很高的應(yīng)用價(jià)值。

To better understand the relationship between SIF and drought stress, researchers have employed comprehensive methods. One Chinese team established an experimental field with an intelligent irrigation control system, combining in-situ measurements with SIF observations to dynamically monitor crop water status.

They subjected winter wheat to four levels of drought stress, collecting real-time SIF data along with photosynthetic rate and other physiological metrics. The results showed a strong positive correlation between SIF and photosynthetic rate. Importantly, SIF responded earlier and more sensitively to mild drought than traditional soil moisture measurements, providing effective early warning capability. This study confirmed the scientific validity of SIF as a drought monitoring indicator and provided valuable data support for precision irrigation in smart agriculture.

實(shí)驗(yàn)田示意圖 / Experimental Field Diagram

不同干旱脅迫下的響應(yīng)（T1、T2、T3和T4分別代表：澆水充足、輕度干旱、中度干旱和重度干旱）。不同字母的值表示在 p < 0.05 處存在顯著差異。圖中的空心塊代表平均值，使用從種植后177~223天收集的數(shù)據(jù)計(jì)算得到。可以看出SIF對(duì)T2輕度干旱的響應(yīng)更加敏感。

Responses under Different Drought Stress Levels (T1, T2, T3, and T4 represent well-watered, mild drought, moderate drought, and severe drought, respectively). Different letters indicate significant differences at p < 0.05. Hollow squares in the figure represent the mean values, calculated from data collected between 177 and 223 days after planting. It can be observed that SIF shows greater sensitivity to mild drought (T2).

不同水分脅迫下，不同參數(shù)的季節(jié)變化。T1、T2、T3和T4分別代表：澆水充足、輕度干旱、中度干旱和重度干旱。所有值均從9點(diǎn)到16點(diǎn)的平均值。橫坐標(biāo)DAP是指種植后的天數(shù)。可以看出SIF則呈現(xiàn)波動(dòng)變化，對(duì)土壤水分更敏感。

Seasonal Variation of Different Parameters under Various Water Stress Conditions. T1, T2, T3, and T4 represent well-watered, mild drought, moderate drought, and severe drought, respectively. All values are averages from 9 a.m. to 4 p.m. The x-axis DAP refers to Days After Planting. SIF exhibits fluctuations and is more sensitive to soil moisture changes.

而另一個(gè)團(tuán)隊(duì)，將新疆地區(qū)作為研究對(duì)象，由于新疆屬于大陸性干旱和半干旱氣候區(qū)域，年降水稀少，蒸發(fā)量大，且農(nóng)業(yè)高度依賴灌溉，因此干旱對(duì)作物生長(zhǎng)的影響尤為顯著。科研人員結(jié)合2001年至2020年長(zhǎng)達(dá)20年的遙感SIF數(shù)據(jù)與當(dāng)?shù)貙?shí)地氣象及植被監(jiān)測(cè)數(shù)據(jù)，利用時(shí)間序列分析、空間疊加和Mann-Kendall趨勢(shì)檢驗(yàn)等統(tǒng)計(jì)方法，深入剖析SIF信號(hào)在不同時(shí)空尺度上的變化規(guī)律。

研究發(fā)現(xiàn)SIF值在干旱初期即顯著下降，其響應(yīng)速度快于傳統(tǒng)植被指數(shù)，能夠第一時(shí)間反映出植物光合作用的受損程度；此外，不同干旱類型對(duì)SIF的影響存在顯著差異，尤其是土壤水分脅迫對(duì)SIF的抑制最為明顯。從空間視角來看，干旱核心區(qū)的SIF波動(dòng)更為劇烈，表現(xiàn)出顯著的區(qū)域差異。

Another research group focused on Xinjiang, a region characterized by a continental arid and semi-arid climate with low annual precipitation, high evaporation, and heavy agricultural reliance on irrigation. Using 20 years (2001–2020) of remote sensing SIF data combined with local meteorological and vegetation monitoring records, they applied time series analysis, spatial overlay, and Mann-Kendall trend tests to examine SIF variations across different spatial and temporal scales.

They found that SIF values declined significantly early in drought events, with a faster response than traditional vegetation indices, thereby promptly indicating reductions in photosynthesis. Different drought types had distinct effects on SIF, with soil moisture stress showing the strongest suppression. Spatially, the drought core areas exhibited greater SIF variability, reflecting pronounced regional differences.

技術(shù)框架 / Technical Framework

類似地，美國(guó)的研究人員通過衛(wèi)星數(shù)據(jù)分析2011年德克薩斯州干旱和2012年中部大平原干旱，發(fā)現(xiàn)SIF信號(hào)都在干旱期間明顯減弱，有效反映了干旱對(duì)植被光合活性帶來的抑制作用。

總的來說，這些研究讓我們看到SIF不僅是“植物光合作用的即時(shí)屏幕"，更是監(jiān)測(cè)干旱脅迫的“靈敏雷達(dá)"，賦能智慧農(nóng)業(yè)提前采取措施，保障作物健康成長(zhǎng)。

Similarly, researchers in the United States analyzed satellite data from the 2011 Texas drought and the 2012 Central Great Plains drought, observing notable SIF declines during these events that effectively represented drought-induced reductions in vegetation photosynthetic activity.

Overall, these studies demonstrate that SIF serves not only as an “instantaneous screen" of plant photosynthesis but also as a highly sensitive “radar" for detecting drought stress, empowering smart agriculture to take proactive measures to safeguard crop health.

愛博能的SIF觀測(cè)系統(tǒng) — 農(nóng)業(yè)“干旱預(yù)警專家"

面對(duì)日益嚴(yán)峻的氣候挑戰(zhàn)，愛博能研發(fā)的日光誘導(dǎo)葉綠素?zé)晒?SIF)監(jiān)測(cè)系統(tǒng)具備諸多優(yōu)勢(shì)：

• 高精度數(shù)據(jù)捕獲，采用高分辨、高靈敏度、高穩(wěn)定性溫漂的國(guó)產(chǎn)化光譜儀；

• 多尺度監(jiān)測(cè)，提供在線式和無人機(jī)載式監(jiān)測(cè)系統(tǒng)；

• 全天候監(jiān)測(cè)能力，在線式監(jiān)測(cè)系統(tǒng)打破時(shí)間和地理限制，實(shí)現(xiàn)連續(xù)動(dòng)態(tài)觀察；

• 定制服務(wù)，滿足不同作物和區(qū)域需求。

EXPONENT’s SIF Monitoring System — An Agricultural “Drought Early Warning Expert"

In response to increasing climate challenges, EXPONENT has developed a solar-induced chlorophyll fluorescence (SIF) monitoring system featuring:

• high-precision data acquisition using domestically produced spectrometers with high resolution, sensitivity, and stable temperature drift;

• multi-scale monitoring with both online and drone-mounted systems;

• all-weather continuous monitoring that overcomes temporal and geographical constraints;

• customizable solutions to meet diverse crop and regional needs.

未來展望

隨著人工智能技術(shù)的發(fā)展，未來將實(shí)現(xiàn)更精準(zhǔn)的作物生理狀態(tài)診斷和產(chǎn)量預(yù)估。

如果你也想了解更多關(guān)于SIF技術(shù)和愛博能的日光誘導(dǎo)葉綠素?zé)晒?SIF)監(jiān)測(cè)系統(tǒng)，歡迎聯(lián)系我們，開啟智慧農(nóng)業(yè)的新篇章！

Future Outlook

With advances in artificial intelligence, future developments will enable even more accurate diagnosis of crop physiological states and yield prediction.

If you want to learn more about SIF technology and EXPONENT’s SIF monitoring system, feel free to contact us and join the new era of smart agriculture!

案例來源 / Source

1. Zhao et al., Exploring the Ability of Solar-Induced Chlorophyll Fluorescence for Drought Monitoring Based on an Intelligent Irrigation Control System. Remote Sens. 2022, 14, 6157.

2. Xue et al., 2024. Response of solar-induced chlorophyll fluorescence-based spatial and temporal evolution of vegetation in Xinjiang to multiscale drought. Front. Plant Sci. 15:1418396.

3. Sun et al., 2015, Drought onset mechanisms revealed by satellite solar-induced chlorophyll fluorescence: Insights from two contrasting extreme events, J. Geophys. Res. Biogeosci., 120, 2427–2440.