The desiccation-tolerant state in seeds is associated with high levels of certain sugars and maturation proteins. The aim of this work was to evaluate the contributions of these components to desiccation tolerance in soybean (Glycine max [L.] Merrill cv Chippewa 64). When axes of immature seeds (34 d after flowering) were excised and gradually dried (6 d), desiccation tolerance was induced. By contrast, seeds held at high relative humidity for the same period were destroyed by desiccation. Maturation proteins rapidly accumulated in the axes whether the seeds were slowly dried or maintained at high relative humidity. During slow drying, sucrose content increased to five times the level present in the axes of seeds held at high relative humidity (128 versus 25 pg/axis, respectively). Stachyose content increased dramatically from barely detectable levels upon excision to 483 pg/axis during slow drying but did not increase significantly when seeds were incubated at high relative humidity. Galactinol was the only saccharide that accumulated to higher levels in axes from seeds incubated at high relative humidity relative to axes from seeds that were slowly dried. This suggests that slow drying serves to induce the accumulation of the raffinose series sugars at a point after galactinol biosynthesis. We conclude that stachyose plays an important role in conferring desiccation tolerance.The remarkable mechanism that allows most mature angiosperm seeds to survive desiccation to extremely low water contents is poorly understood. Among the protective components that have been proposed to be important in the acquisition of desiccation tolerance during seed development are proteins and soluble sugars. The group of proteins known as Late Embryogenesis Accumulating, or Lea (13), proteins include some that accumulate during the maturation drying phase of seed development. Some of these maturation proteins have been correlated with the ability of the seed to progress into seedling growth (29), whereas others have been correlated with desiccation tolerance (2, 4). However, some additional process is apparently necessary for the development of desiccation tolerance. We have shown that maturation protein accumulation alone is not sufficient to confer desiccation tolerance in developing soybean (4 characteristic of mature orthodox seeds (1). They have been implicated by correlation as adaptive agents for desiccation tolerance during seed development and germination (9,18,19). In particular, cultivars of soybean (Glycine max) accumulate high levels of the raffinose series of oligosaccharides, particularly stachyose, in addition to sucrose (12,18,21,31). Evidence for the protective role of soluble sugars has also been inferred from model systems (7, 11). The soluble sugar, trehalose, protects cytosolic components in yeast against desiccation-, frost-, and heat-induced damage in vivo (34). It is thought that the hydroxyl constituents of sugars may replace the hydration shell around membranes and thus prevent structural damage a...

The growth rate of excised soybean (Glycine max [L.] Merrill) embryos grown in liquid culture increased linearly as photoperiod was increased from 0 to 20 h at an irradiance of 9 W m-2 measured between wavelengths of 700-850 nm from clear incandescent lamps. When irradiance levels were varied between 0.1 and 1.7 W m-2, the maximum growth rates of embryos occurred at ca. 0.5 W m-2 at both 10- and 16-h photoperiods. When the light source was changed from clear incandescent lamps, with a red (600-700 nm) to far-red (700-770 nm) ratio of ca. 1.07, to a BCJ incandescent lamp (Corning Glass dark red, transparent envelope and a red to far-red ratio of ca. 0.19), the growth rate of embryos slowed. These results are consistent with a high irradiance response for growth of soybean embryos.