The influence of depth (0 to 20 cm) and duration (1 to 31 months) of burial on the deterioration, germination, and viability of common crupina (Crupina vulgaris Cass. ♯ CJNVU) was investigated in the field. Germination and decay of achenes prior to removal from the field were greater at 0- to 10- (7%) and 0- to 15- (21%) cm burial depths than at the 20-cm burial depth for 1980 and 1981 seedlots, respectively. After 25 months of burial, 41 and 26% of the achenes had not deteriorated for the 1980 and 1981 seedlots, respectively. Germination was greatest for nondeteriorated achenes recovered from 3- and 20-cm (63%) and least for the 10-cm burial depth (44%). Common crupina achenes recovered from the field over 25 months of burial exhibited a pronounced periodicity of germination, which was related to induced winter dormancy. The viability of achenes decreased linearly from 90 to near 0% over 31 months of burial.

Many research questions focused upon seed dormancy and germination remain unanswered due to problems created by inappropriate assumptions concerning the design and implementation of experiments. Lack of attention to the genetic background and growing conditions required for seed production and subsequent storage may compromise an investigator's ability to pool data or assimilate data trends due to variability in seed performance from year to year. Seed aging events during the afterripening process can be mistaken for those involved in the transition from the dormant to nondormant state. After imbibition, inaccurate criteria for and scoring of the germination event may lead to confusion of seed vs. seedling physiology and biochemistry. In addition, a sufficient number and proper spacing of data points during timecourse experiments are required to properly stage a sequence of events. Studies comparing dormant vs. nondormant seeds must be supplemented with kinetic experiments examining the effect of a dormancy-breaking treatment upon the transition between the dormant and nondormant states. In comparisons of the relative efficacy of various dormancy-breaking chemical treatments, the physical properties of substances under evaluation (e.g. lipophilicity) should be considered. In addition, since many dormancy-breaking chemicals are toxic to vegetative growth, there is a danger of introducing pharmacological artifacts that confuse interpretation of the results obtained. These toxic properties also necessitate the use of viability tests during construction of dose-response curves to avoid confusing seed death with dormancy. Seed scientists must also avail themselves of the extensive literature on developmental arrest in other organisms, which may generate fresh ideas for experimentation.

Some of the seed-evolved volatiles, which were mainly composed of methanol, acetaldehyde, ethanol and acetone, caused the loss of seed germinability during storage. In general, the deleterious effects of the volatiles increased with increasing RH and temperature during storage. Acetaldehyde had the strongest deleterious effect regardless of RH and temperature, while ethanol caused seed deterioration only at high RHs. Acetone was slightly deleterious to some species, while methanol was almost inert in most seeds. Various aldehydes applied during storage showed some toxicity to seed germinability, which decreased, except for 3-methylbutanal, with increasing molecular size, suggesting that the endogenous volatile compounds with an aldehyde group cause seed deterioration. On the other hand, the contents of volatile compounds in seeds were higher when they were stored at 44% RH (water sorption zone 2), than when stored at 12% RH (water sorption zone 1). Acetaldehyde, the most deleterious volatile, was more abundantly accumulated within the seeds stored at −3.5°C than at 23°C. Based on these facts, it is suggested that endogenous volatiles, especially acetaldehyde, may be an important factor that accelerates seed deterioration which often occurs under lower RHs and/or temperatures throughout long-term storage.

When seeds deteriorate, they lose vigour and become more sensitive to stresses upon germination. Eventually seeds lose the ability to germinate. The factors which determine the rate of this ‘aging’ are the temperature and moisture content at which seeds are stored and an ill-defined parameter, seed quality. While it has been known for many years that manipulation of these factors influences the longevity of seeds, the precise interactions among them are so poorly understood as to preclude the prediction of longevity for a particular seed lot. Concepts from studies of materials and food stability can be applied to seed aging research, and this may help us take a more integrative approach to understanding the kinetics of seed deterioration. These concepts describe the physical environment of the seed matrix in response to changing water contents and temperature. Water activity models describe the state of water in the seed, while the glass models describe the state of the aqueous solution. Both models presume that changes of state affect the nature and kinetics of chemical reactions. Thus, the physical and chemical environment within the seed are inextricably linked.

Osmotic priming in a polyethylene glycol solution (300 g/kg water) for 48 h resulted in a partial loss of desiccation tolerance for seeds of Vigna radiata (L.) Wilczek (mung bean). The percentage of germination began to decrease after primed seeds were dried down to water contents less than 0.06 g/g DW. As compared with control seeds, primed mung bean seeds also had poorer storage stability. The decline of storage stability after osmotic priming was correlated with the modifications of seed water sorption properties. Priming significantly increased the amount of water associated with the weak water-binding sites, and reduced the amount of water associated with the strong binding sites and multi-molecular binding sites in seed tissues. The enhancement of molecular mobility in seeds, as a result of such water redistribution, probably accelerates seed deterioration and decreases storage stability.

The premise of this paper is that the chemical potential of water strongly influences aging reactions in seeds, and that there will be an optimal chemical potential of water for seed longevity. If this is true, the optimum moisture content for storage and the optimal drying protocols should vary with the storage temperature, but should be predictable from water sorption isotherms. Isotherms for pea, soybean and peanut are given for temperatures between 65° and −150°C. Relative humidity/moisture content relationships were determined directly for temperatures between 5° and 50°C using saturated salt solutions. At extreme temperatures, isotherms were calculated from heat capacity measurements using differential scanning calorimetry or extrapolations of van't Hoff analyses. The family of isotherms was used to predict optimum moisture contents at storage temperatures between 65°C and −150°C. The optimal moisture contents for these three species are consistently shown to increase as the storage temperature is lowered.

Artificial aging of wheat grains (Triticum aestivum cv. Mercia) for 3 d resulted in the gradual loss of seed vigour without loss of viability, but the latter decreased rapidly over the next 24 h. Loss of vigour was expressed as a delay in germination i.e. an increasing ‘lag’ period with aging before the onset of radicle emergence, but the subsequent rate of seedling growth was not affected. There was an overall decrease in the incorporation of 35S-methionine into protein in aged embryos, and associated with the aging-induced delay in the completion of germination (i.e. start of radicle emergence) there was a delay in the production of certain polypeptides. In embryos of both non-aged and aged seeds these polypeptides appeared just prior to radicle emergence but several of these were never synthesized in embryos from non-viable seeds. The synthesis of mRNA coding for in vitro translated polypeptides, or groups of polypeptides, was similarly delayed in lowvigour embryos. Furthermore, some polypeptides were identified which were induced by the accelerated aging treatment. It is concluded that a reduced level of protein and mRNA synthesis in the embryos of low-vigour seeds may result in the delay in the accumulation of specific of mRNAs and polypeptides which are needed for the normal completion of germination, i.e. radicle emergence.