A Comparative Analysis of Quantitative Metrics of Root Architecture

Table 1

Aggregate phene metrics, definition, and method of obtaining them from SimRoot output.

Parameter

3D

2D

Description

Measurement

Total length

Y

Y

Summed length along the whole root system

Calculated from SimRoot output

Total area

Y

Y

Summed surface area of the whole root system

Calculated from SimRoot output

Total volume

Y

Y

Summed volume of the whole root system

Calculated from SimRoot output

Maximum width

Y

Y

Maximum horizontal width of the whole root system

Calculated using minimum enclosing circle algorithm in

Maximum depth

Y

Y

Maximum vertical depth of the whole root system

Calculated from SimRoot output

Median no. of roots

Y

Y

Median no. of roots from root counts

Calculated from SimRoot output

Maximum no. of roots

Y

Y

No. of roots at the 84th percentile of a sorted list (smallest to largest) of root counts

Calculated from SimRoot output

Bushiness

Y

Y

Ratio of the maximum no. of roots to the median no. of roots

Calculated from SimRoot output

Volume distribution

Y

Y

Ratio of the volume of the root system contained above one-third depth of the root system to the volume of the root system contained below one-third depth of the root system

Calculated from SimRoot output

Convex hull volume

Y

Y

Volume of the convex hull that encompasses the whole root system

Obtained using Convhulln function in

Convex hull area

Y

Y

Surface area of the convex hull that encompasses the whole root system

Obtained using Convhulln function in

Solidity

Y

Y

Ratio of volume to convex hull volume

Calculated

Major ellipse axes

Y

N

Length of major axis of an ellipse best fit to overall shape and size of root system

Obtained using minimum volume enclosing ellipse algorithm in

Minor ellipse axes

Y

N

Length of minor axis of an ellipse best fit to overall shape and size of root system

Obtained using minimum volume enclosing ellipse algorithm in

Ellipse axis aspect ratio

Y

N

Ratio of major axis of ellipse to minor axis

Calculated from minor ellipse axes and major ellipse axes

Fractal dimension (FD)

Y

Y

Measure of root complexity. Fractal dimension expresses the space filling properties of a structure (e.g., root system) and is associated with branching pattern

Obtained using box count code written in

Fractal abundance (FA)

Y

Y

Measure of root complexity. Fractal abundance is associated with the volume of space explored