Visualisation of moisture distribution during development of rice caryopses (Oryza sativa L.) by nuclear magnetic resonance microimaging

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 ti ssues, especially of the embryo, the pericarp vascular bundle, and the endo sperm, up to 25 days after anthesis. Outlines of these structures, as revea led by their moisture distribution pattern, were largely consistent with Va rious earlier morphological observations. Water observed in a relatively na rrow zone in the center of the caryopsis 25 days after anthesis was conside red 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 a bove assumption. A striped pattern of water was observed on the surface of the endosperm in the three-dimensional images reconstructed from maximum in tensity projections of the spikelets. This finding supports a previously st ated hypothesis that water flows from the pericarp vascular bundle onto the nucellus. (C) 2001 Academic Press.