Western blot analysis using antiserum raised against the lysine-rich box common to dehydrins, one class of late-embryogenesis-abundant (LEA) proteins, was used to study the abundance of heat-stable ‘dehydrin-like’ proteins during development and water stress in Ranunculus sceleratus L. achenes (seeds). A 61 kDa dehydrin-like protein was apparently limited to immature seeds (fresh and dried) which had not attained full desiccation tolerance. In contrast, lower-molecular-mass proteins which were induced by desiccation were found only in more mature seeds. The molecular masses of desiccation-induced proteins changed during seed development from 18 kDa in seeds harvested at 13 days post anthesis (DPA) to 31 kDa at harvest maturity, 21 DPA.

Placing seeds at 21 DPA in polyethylene glycol (PEG) at −1.5 MPa reduced seed moisture content and was accompanied by accumulation of 31 kDa protein. This protein was no longer detected when the seeds were transferred to water. In seeds harvested at 13 DPA, PEG induced the synthesis not only of 18 kDa protein (which is associated with dried seeds at this developmental stage), but also of 28 kDa and 31 kDa proteins. These dehydrin-like proteins were also synthesised when seeds at 13 DPA were imbibed in water. These and other data indicate that both quantitative and qualitative changes in dehydrin-like proteins can occur in R. sceleratus, depending on seed maturity and the degree and duration of water stress.

Storage proteins (2S, 7S and 11S) are synthesized at the mid- to late stages of development in alfalfa seeds, mainly within the embryos. Mature dry seeds cannot synthesize these proteins upon subsequent germination and growth. When embryos were isolated from the seed during development (stages VII and VIII) and placed on water or nutrient medium, they germinated. They exhibited a pattern of protein synthesis which was identifiable as germinative/post-germinative, and was identical to the pattern synthesized in embryos of germinated dry seeds, and of embryos from seeds that were subjected to drying prematurely at stages VII and VIII. When, after 48 h from the start of imbibition, abscisic acid or osmoticum was introduced to germinated embryos isolated at stage VII and not desiccated, the synthesis of the 11S storage protein was restored to a rate comparable to that of stage-VII embryos before isolation. This was accompanied by an increase in transcription of the 11S storage protein gene. Transfer of germinated stage-VII embryos, which had first been desiccated, to abscisic acid or osmoticum 48 h after imbibition started did not result in any restoration of storage protein synthesis. Thus, desiccation, prematurely or at maturation, off-regulates storage protein synthesis and within the embryos this process is no longer responsive to abscisic acid or osmoticum.

Seeds were collected at weekly intervals from mid-maturation to the fully ripened stage. As seed development progressed, desiccation tolerance increased. Desiccation tolerance of C. lansium seeds was greatest at 67 days after anthesis (DAA), when they tolerated air drying for 9 days; 74 DAA was considered as physiological maturity, and their full viability was only maintained for up to 3 days of drying; overripened seeds (88 DAA) had the lowest desiccation tolerance. In L. chinensis, the desiccation sensitivity of seeds at 98 DAA (fully mature) was higher than that at 84 and 91 DAA (less mature); among the excised embryonic axes at different developmental stages, the less mature ones were less sensitive to desiccation than the fully mature ones; excised embryonic axes of the same stage were more tolerant of desiccation than whole seeds.