Root System Architecture (RSA) of Prairie Grasses Under Acidic Soil Conditions

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1 Root System Architecture (RSA) of Prairie Grasses Under Acidic Soil Conditions Prepared for: Dr. Emmanuel Dzantor, Tennessee State University, May 211

2 Three Types of Prairie Grasses Were Grown in Number 5 Pots Switchgrass (Panicum virgatum L.) Eastern Gamagrass (Tripsacum dactyloides (L.) L.) Big Bluestem (Andropogon gerardii Vitman)

3 Experimental Conditions Four seeds of each species were planted in each pot in TSU greenhouses. Soil ph for each pot was maintained at one of three acidity levels: 4.5pH, 5.5pH and 6.5pH. Plants were grown under same greenhouse conditions for over nine months.

4 Experimental Conditions (cont) Plants were extracted from pots, root systems were manually separated, soil was washed off with gentle water spray, individual roots were wrapped in moist towels and placed in sealed plastic bags, and shipped for overnight delivery to Phenotype Screening Corporation. Roots were left sealed until just prior to imaging. Roots were X-ray imaged over a period of 15 minutes each. There were six replicates for each treatment.

5 Basic Imaging Concept

6 Switchgrass Root System X-ray Images 4.5 ph 6.5 ph

7 Gamagrass Root System X-ray Images 4.5 ph 6.5 ph

8 Big Bluestem Root System X-ray Images 4.5 ph 6.5 ph

9 Stereo and Mono Images Were Generated of Each Plant Switchgrass

10 Very fine structure of RSA is captured in each plant root image. Switchgrass

11 Sophisticated Processing Is Applied to Enhance Features of Interest Switchgrass

12 Image Analysis Techniques Were Used to Characterize the RSA by Root Size Classes Original Image Coarse Roots Medium Roots Fine Roots < 2.9 mm 725u to 2.5 mm 181u to 62u Global RSA traits were independently determined at each root class size.

13 Transect Analysis was Used to Assess RSA Distribution by Depth The image is analyzed at specific depths. The number of roots crossing each transect is counted and the position and diameter of each root at the crossing is determined. The square of the root diameter is considered proportional to mass. The sum of all of the areas of roots gives a value proportional to total mass at that depth. The width of the root system is also determined at each transect depth. We can then determine the count density and the mass density at each depth. Global characteristics such as projected area, total-root-length, total-root-lengthdensity are also determined for each plant.

14 Average Total-Root-Length Drop Page Fields Here 8 Average of TRL (mm) Treatment Big Bluestem Gamagrass Switchgrass Species

15 Average Total Root Length Density Drop Page Fields Here.35 Average of TRLd (mm/mm3) Treatment Big Bluestem Gamagrass Switchgrass Species

16 Approximate Root Mass Extracted from X-ray Images (arbitrary units) Drop Page Fields Here 7 Sum of SqRtdiam (mm2) Treatment Big Bluestem Gamagrass Switchgrass Species

17 Coarse Fine Medium Coarse Fine Medium Coarse Fine Medium Silhouette Area of Root System ( Root System Extent ) Drop Page Fields Here 2 Average of Projected Area Size Treatment Coarse Coarse Fine Fine Medium Medium Big Bluestem Gamagrass Switchgrass Species

18 Approximate Root Mass Distribution by Individual Gamagrass Plant Species Gamagrass.6 Average of SqRtdiam (mm2) TDepth (mm) TSUGG451A TSUGG451B TSUGG452A TSUGG452B TSUGG452C TSUGG452D Plant ID Treatment

19 Coarse Fine Medium Coarse Fine Medium Coarse Fine Medium 1.6 Average Root Diameter by Size- Drop Page Fields Here Class and by Treatment Average of Rtdiam (mm) Size Treatment Coarse Coarse Fine Fine Medium Medium Big Bluestem Gamagrass Switchgrass Species

20 Number of Root Crossings Over All Transect Depths by Root-Size-Class Drop Page Fields Here 1 Count of TRC Size Coarse Fine Medium Big Bluestem Gamagrass Switchgrass Big Bluestem Gamagrass Switchgrass Treatment Species

21 Big Bluestem Gamagrass Switchgrass Big Bluestem Gamagrass Switchgrass Big Bluestem Gamagrass Switchgrass Big Bluestem Gamagrass Switchgrass Big Bluestem Gamagrass Switchgrass Big Bluestem Gamagrass Switchgrass 25 Count of TRC Number of Root Crossings at Measured Drop Transect Page Fields Here Depths TDepth (mm) Coarse Fine Medium Coarse Fine Medium Treatment Size Species

22 TSUBB451A TSUBB451B TSUBB451C TSUBB451D TSUBB451E TSUBB452A TSUBB651A TSUBB651B TSUBB652A TSUBB652B TSUBB652C TSUBB652D TRL by Individual Big Bluestem Plant Species Big Bluestem 6 Average of TRL (mm) Treatment Plant ID

23 TSUGG451A TSUGG451B TSUGG452A TSUGG452B TSUGG452C TSUGG452D TSUGG651A TSUGG651B TSUGG651C TSUGG652A TSUGG652B TSUGG652C TRL by Individual Gamagrass Plant Species Gamagrass 1 Average of TRL (mm) Treatment Plant ID

24 TSUSG451A TSUSG451B TSUSG451C TSUSG451D TSUSG452A TSUSG452B TSUSG651A TSUSG651B TSUSG651C TSUSG652A TSUSG652B TSUSG652C TRL by Individual Switchgrass Plant Species Switchgrass 8 Average of TRL (mm) Treatment Plant ID

25 Root System Width at Increasing Depths of TSUBB451A Plant ID TSUBB451A Species Big Bluestem 35 Average of WidthatDepth(px) Size Coarse Fine Medium TDepth (mm)

26 Number of Root Crossings per Root System Width (Count Density) at Increasing Depths of TSUBB451A Plant ID TSUBB451A Species Big Bluestem.3 Average of CountDensity(#/px) Size Coarse Fine Medium TDepth (mm)

27 Approximate Root Mass Density Distribution at Increasing Depths of Plant ID TSUBB451A TSUBB451A Species Big Bluestem.6 Average of ApproxMassDensity(mm2/px) Size Coarse Fine Medium TDepth (mm)

28 Approximate Root Mass Density Distribution at Increasing Depths of Plant ID TSUBB451A.35 Species Big Bluestem Average of ApproxMassDensity(mm2/px) TSUBB451A Fine Fine Roots Only!!! Size Fine TDepth (mm)

29 Conclusions Detailed, clear, high-resolution images are possible with pot-grown or field harvested washed root systems. Global descriptors of RSA can be automatically extracted from X-ray Images. Global descriptors of RSA can be determined independently for each root size class. RSA distribution as a function of root depth can also be derived and gives unique insight into root system morphology. Image analysis can differentiate root system growth between species and between treatments within and between species.