Determining Root Hydraulic Conductance of Container Grown Plants as an Assessment of Root Mass

Measuring hydraulic conductance and resistance of plant roots has been an effective way to quantify root system development and productivity of field-grown trees. Root hydraulic properties can vary with species, drought, temperature, soils, etc. With advancing technologies, new devices have been developed to quantify root hydraulic properties with rapid-flow measurements.  The hydraulic conductance flow meter (HCFM) is one such device that was developed to measure hydraulic properties of undisturbed root systems of woody plants in soils but never on herbaceous plants in containers.  The objectives of this study were: 1) determine if the HCFM can measure root conductivities of herbaceous plants grown in containers and; 2) determine if root conductivities can be correlated to root dry mass as a technique to assess undisturbed root system development of container-grown plants.  Chrysanthemum ‘Garden Alcala Red’ were grown in peat-based substrates amended with either 20% perlite or 20%, 30%, or 40% shredded pine wood (SW). SW was produced by hammer milling freshly shredded loblolly pine trees (Pinus taeda) through a 6.35 mm screen. Six containers were filled with each individual substrate and one Chrysanthemum plug was planted into the center of each container.  Plants were grown for four weeks before the HCFM was used to measure root conductance followed by the roots being washed for dry weight determinations.  Hydraulic conductance of all plants in all substrates was effectively determined using the HCFM, illustrating the potential for this technique to be used on container-grown plants. For each substrate and plant replication, root conductance was plotted against root dry weight.  Chrysanthemums grown in all substrates exhibited a positive correlation between increasing root dry mass and increasing root conductance. Plants grown in the 30% SW substrate had the strongest correlation with a linear increase in root conductance and root dry weight. Plants in the other substrates exhibited non-linear relationships but were still positively correlated.  These data indicate that measuring root conductivities of container-grown plants can be a possible tool in assessing root development, productivity and mass in horticultural crops. Assessing root conductance could be a new parameter in studying plant productivity and root vigor during crop production.