Root growth following transplanting allows a plant to exploit water and nutrient resources in the soil backfill (landscape) or container substrate and thus is a critical factor for transplant survival. The Horhizotron, a horizontal root growth measurement instrument, has been developed and evaluated for use in measuring root growth under a variety of root environments. The design of the Horhizotron includes four wedge-shaped glass quadrants that extend away from a plant's root ball allowing measurement of roots as they grow out from the original root ball. The substrate in each quadrant can be modified in order to evaluate the effect of substrate or root environment on root growth. Materials used for construction were lightweight, durable, easy to assemble, and readily available from full service building supply stores. Units were suitable for use on a greenhouse bench or outdoors in contact with the ground. Horhizotrons provided a simple, nondestructive method to measure root growth over time under a wide range of rhizosphere conditions.

TM provides a simple, non-destructive method to measure root growth under a variety of rhizosphere conditions. The ease with which the root environments can be manipulated when using this system suggests that this technique will have broad application for use in horticultural research on factors affecting landscape establishment; soil or container substrate chemical and physical properties; effects of plant growth regulators and herbicides on root growth; environmental effects on root growth; mycorrhizal associations; and propagation techniques. Nature of Work: Following transplanting into the landscape, the majority of plant roots initially grow horizontally into the soil, substrate, or backfill (2). Exploitation of the surrounding landscape soil or container substrate is critical for the plant to obtain water and mineral nutrients needed for healthy growth and development. Many techniques have been developed to measure root growth; however, most focus on the vertical distribution of roots through the soil, and they can be expensive, time consuming, difficult to construct, or destructive (1). There is a need to develop a technique that can easily monitor horizontal root growth under a wide range of soil, environmental, and plant conditions. The Horhizotron TM (horizontal root growth measurement instrument), a technology recently developed cooperatively at Auburn University and Virginia Tech, provides a simple, non-destructive method to measure root growth over time in a wide range of root environments. This paper describes construction criteria for the Horhizotron TM