| This work examines maturation of soybean Glycine max (L.) Merrill cv. Anoka fruit from final dry weight accumulation when pods are still green to the terminal stage of desiccation when pod walls and seeds are brown and yellow respectively. Fruit development was analyzed in terms of water content, conductance as measured by dye flow, and water potential of fruit parts. When pod walls and seed coats lose all greenness, dye flow into fruit stops first at the seed coats, followed by the funiculus, pod wall, and pod wall vascular bundles. Major pod wall desiccation precedes that of the seeds and is reflected by decreasing water potentials and browning of the pod wall. As the pod wall cavity dries in response to pod wall dehydration, major seed desiccation starts and is also reflected by decreasing water potentials. The findings that during desiccation water potentials of pod walls are more negative than water potentials of seeds suggest that seed moisture evaporates into the pod wall cavity, is absorbed by the pod wall membrane, and then is evaporated from the pod wall into the atmosphere. This conclusion is supported by results showing delay of pod wall and seed desiccation by high humidity. High humidity delays pod wall yellowing and prevents browning unless browning had started prior to the high humidity treatment, but it does not alter seed (coat and embryo) yellowing or hilum darkening. Even though desiccation does not seem to control seed color change, it does control pod wall browning and seed germination within the fruit (vivipary), since seeds are sometimes viviparous when desiccation is delayed for an extended period. |
