Visualisation of Moisture Distribution during Development of Rice Caryopses (Oryza sativa L.) by Nuclear Magnetic Resonance Microimaging

Abstract

The moisture distribution in developing rice caryopses was visualised with nuclear magnetic resonance (MR) microimaging. Rice plants (Oryza sativa L. cv. Koshihikari) were grown outdoors in pots, and spikelets were sampled at various times after anthesis. Clear images could be obtained from young tissues, especially of the embryo, the pericarp vascular bundle, and the endosperm, up to 25 days after anthesis. Outlines of these structures, as revealed by their moisture distribution pattern, were largely consistent with various earlier morphological observations. Water observed in a relatively narrow zone in the center of the caryopsis 25 days after anthesis was considered to indicate a route for water supply or drain for the embryo. The fact that this band of water touched the corner of the embryo strengthened the above assumption. A striped pattern of water was observed on the surface of the endosperm in the three-dimensional images reconstructed from maximum intensity projections of the spikelets. This finding supports a previously stated hypothesis that water flows from the pericarp vascular bundle onto the nucellus.