SUM MARYMagnetic resonance (MR) imaging was used to study water absorption from fine, moist sand by the taproot, firstorder lateral roots, and fine roots of 9-month-old loblolly pine seedlings. Magnetic resonance imaging provides the opportunity for repeated non-destructive measurements of water uptake by roots growing in a solid medium such as sand. Root systems of container-grown seedlings were pruned to a taproot, one or two first-order laterals and attached fine roots, and were planted in small containers. Reference tubes filled with a mixture of CuSO^/D^O were placed in each container in the field of view. Roots of individual seedlings were repeatedly imaged at approximately 3 h intervals. Water uptake by individual roots was measured and uptake was calculated based on biomass, root length, and surface area. Based on weight and surface area, but nor on root kngth, fine roots were more efficient than the lateral or taproots in water uptake.Measurement of water content in MR images of wet sand was confirmed by the imaging of sand phantoms. These phantoms were tubes filled with fine sand at varied water contents (5-25%). Additional rubes of CuSOŵ ith D^O were also imaged, A linear relationship between signal intensity of moist sand (normalized against the CuSO^/DaO) and water content was demonstrated {R^ = 0-97). Fitting the normalized signal intensity of the sand to the calculated linear regression allowed calculation of the water content of the sand.

Magnetic resonance imaging was used to study sand containing various amounts of water and roots of loblolly pine planted into similar sand. Spin-lattice (Ti) relaxation times of sand with water contents ranging from 0 to 25% (wt/wt) ranged from 472 to 1265 ms and increased with water content. Spin-spin (T2) relaxation times ranged from 54 to 76 ms and did not change in a discernible pattern with water content. Based on water content and measured Ti and 72 values, the signal intensity ofsand/water images was predicted to increase with water content in a linear fashion, with the slope of the lines increasing with the time of acquisition repetition (TR). Measured signal intensity from images of sand with various water contents was found to follow a similar pattern.

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