Transcript
Stress detection in plants D. Michael Glenn and James Kim USDA-ARS-Appalachian Fruit Research Station Kearneysville, WV
Problem: How can the status of plant stress be measured rapidly and accurately?
Technology to measuring plant stress: • Reflectance of radiation (visible, NIR) – A measure of photosynthesis efficiency
• Plant temperature (absorbance of IR) – A measure of transpiration supply to meet environmental demand for water
Spectral Image Response of Apple Chlorophyll absorbance
Hyperspectral Response to Water Stress Spectral Image @671nm Healthy plant (100% water applied)
Stressed plant (45% water applied)
Spectral Index R800 R680
NDVI (Normalized Difference Vegetation Index) R800 R680 SRI (Simple Ratio Index)
R900 R680
Broadband Greenness
R800 R680
EVI (Enhanced Vegetation Index) 2.5 R800 6 R680 7.5 R450 1 ARVI (Atmospherically Resistant Vegetation Index)
R800 (2 R680 R 450) R800 (2 R680 R 450) R750 R705
Red Edge NDVI R750 R705 Modified Red Edge NDVI Modified Red Edge SRI Narrowband Greenness
R750 R705 R750 R705 2 R445 R750 R445 R705 R445
R740 VOG REI (Vogelmann Red Edge Index) 1 R720
R734 R747
VOG REI 2 R715 R726
Light Use Efficiency
Dry or Senescent Carbon
Canopy Water Content
VOG REI 3
R734 R747 R715 R720
PRI (Photochemical Reflectance Index)
R531 R570 R531 R570
PSRI (Plant Senescence Reflectance Index)
R680 R500 R750
R900 WI (Water Index) R970
Transpiration cooling-the evaporation of water from a surface reduces the surface temperature Water stressed l 26.0 ˚C
Canopy temperature reduced up to 8˚C.
Transpiration cooling is driven by the vapor pressure deficit (ƒ [RH, light and air temperature])
Non-stressed control 24.4 ˚ C
0.8 0.7 0.7 0.6 0.6 0.5 0.5 0.4 0.4 0.3
6 5/4
5/4
SRI
4
5/7 5/11
5/7 2
5/11
0
6/4 100% 90%
75%
60%
45%
6/4 100%
90%
75%
60%
45%
Water treatment/replacement (% of maximum)
•All indices of plant stress and plant water status demonstrated a response to the reduced water availability. •None provided a consistent response over sampling dates
VOG REI 1
1.4 5/4
1.2
5/7 1.0
5/11
0.8
6/4 100% 90%
75%
60%
45%
0.30 Red Edge NDVI
NDVI
Hyperspectral Image Response
5/4
0.20
5/7 0.10
5/11
0.00
6/4 100% 90%
75%
60%
45%
Trimble’s GreenSeeker-an ‘active’ NDVI sensor
Engineering limitations of the GreenSeeker sensor were identified
Plant Stress Detection (Greenhouse Test) Multispectral camera
NDVI sensor Color camera Range finder
Thermal imager
7
% Photosyntehsis reduction
100%
Photosynthesis (umol/m2/s)
6 5 4 3 2 1 0 -1
0
0.2
0.4
0.6
0.8
80% 60%
40% 20% 0% 100%
1
NDVI
5/13
0.9
NDVI (Greenseeker)
5/14 0.8 5/25 0.7
6/8 6/11
0.6
6/15 0.5 0%
20%
40%
60%
Photosynthesis reduction
80%
100%
6/18
75% 65% 55% Water treatment
45%
•NDVI values alone do not reflect the photosynthetic rate •Expressing the photosynthetic rate as a % of maximum does not overcome sampling date variation •However, variation diminishes in NDVI as stress is reduced. •Growers are most concerned about identifying initial stress where NDVI >0.8
Multi-modal Sensor System
Irrigated
Non-Irrigated
The next step? Integrate spectral and thermal data with whole tree photosynthesis to develop an absolute measurement of plant stress status PAR
Photosynthesis
90 80
2000
70 60
1500 50 40 1000 30 20
500
Whole tree photosynthesis (g CO2/hr)
Photosynthetically active radiation (umol/m2/s)
2500
10 0 145 145 146 146 168 168 169 170 170 171 171 189 190 190 191 191 192 192 241 242 242 265 265 266
0
90
40
80
35
70
30
60
25
50
20
40
15
30
10
20
5
10
0
0 Day of the year
Whole tree photosynthesis (g CO2/hr)
Day of the year Vapor pressure deficit photosynthesis
145 145 146 146 168 168 169 170 170 171 171 189 190 190 191 191 192 192 241 242 242 265 265 266
Vapor pressure deficit (mbars)
45
Summary • What we know: – Environmental conditions change diurnally – Varying degrees of plant stress can be identified with NDVI and canopy temperature – Neither NDVI or canopy temperature provide an absolute measurement of plant stress – NDVI and canopy temperature both provide independent information on plant stress but have not been integrated.
• What we need: – Reliable, non-contact, sensor array to measure absolute plant stress status – A sensor system that will integrate environment, NDVI, and canopy temperature with photosynthesis data measured in short time frames and integrated into a daily response.
Economic evaluation and commercialization are in the future.
