Published seed storage data for 92 species derived frotn 13 localities were subjected to probit analysis to determine the half-viability period (P.^o) for each satnple. Estitnates of half-viability petiod for each species averaged over all 13 localities were calculated using a least square tneans procedute applied to known values for the half-viability period for each species at each of its storage stations. The results reported hete represent an itiitial step in the objective organization of seed longevity data.

When seeds of soybean were subjected to accelerated aging, the amount of total lipid which was extracted from the whole seed increased with "age," whereas the extractable phospholipid decreased slightly. This small decline primarily reflected changes in the amounts of phosphatidylchoUne and phosphatidylethanolamine. The levels of unsaturated fatty acids in the whole seed and in the seed axis showed no decline during aging. Similarly, the fatty acids in a polar Upid extract from the whole seed showed Uttle change in unsaturation. These results suggest that oxidation of seed Upids may be unrelated to the process of seed aging.The aging of dried seeds in storage is thought to be accompanied by changes in membranes (8, 24) and nucleic acids (15). Alterations in the membranes of aged seeds are considered to lead to a greatly enhanced leakage of solutes during seed imbibition (2, 13). This may be indicative of an inability to re-form coherent membranes during rehydration of the seed, resulting in loss of vigor and lack of germination. Changes in dry or rehydrated membranes of aged seeds have been noted at the ultrastructural level (6). Lesions in nucleic acids may also be important in deterioration of seed (15), although probably less significant during the first minutes of imbibition when protein and nucleic acid synthesis is probably minimal.Several workers have argued that the alterations to seed membranes during aging may result from peroxidation (10, 24). Autooxidation of polyunsaturated fatty acids leads to free radical formation and possible peroxidative damage to lipids, proteins, and nucleic acids. Peroxidation of membrane lipids gives rise to increased permeability of artificial bilayers (23) and a decrease in membrane fluidity (5). Spencer et al. (20) noted an increased level of oxygenated fatty acids in seeds of Cichorium and Crepis during long term storage, although these workers supplied no germination data. Most studies have been performed using systems of accelerated aging, in which the symptoms of natural aging are induced over a relatively short time span by exposing the seeds to conditions of high temperature and humidity (4). Koostra and Harrington (10) applied TLC to lipids extracted from cucumber seed and suggested that any phosphorus-containing spot which remained immobile in their solvent system was probably a peroxidized phospholipid; applying this principle, they indicated that peroxidation increased severalfold during aging, peroxidized phospholipids representing over 20%o of the total phospholipids in seeds rendered nongerminable. UV spectroscopy of seed fatty acids of Protea compacta by Van Staden et al. (22) ysis can be considered only semiquantitative. Harman and Mattick (7) studied accelerated aging of pea seeds and found that the decrease in germination rate was paralleled by a pronounced decline in linoleic (C 18:2) and linolenic (C 18:3) acids whereas the saturated and monoenoic fatty acids remained unchanged. They suggested that this decline in dienoic and trienoic fatty a...

1985, Organic free radical levels in seeds and poiien: The effects of hydration and aging, -Physiol, Plant, 64: 88-94, Io view of their possible role in oxidative deterioration of seeds and poiien, organic free radicals were measured by electron spin resonance in embryonic axes and cotyledons of soybean [Glycine max (L,) Merr,j, embryo and endosperm fractions of corn IZea mays L,] and pollen of cattail [Typha latifoiia L.]. A pronounced declioe in the radical signal ensued when hydration increased above about 7% (wet weight basis) io both the seed materials and in pollen. Moderate hydration of the soybean axis followed by drying led to a small decrease in organic free radicals compared to untreated material, especially if the desiccation step was performed under oitrogen. In a comparison of soybeans of various ages uoder normal storage, organic free radical levels in the axis showed little or no increase witb age. In marked contrast, over 5 days of accelerated aging at 40°C and near-saturating humidity, organic radical levels approximately doubled in the axis. This pronounced increase in free radical content was not associated with a decrease in the proportion of polyunsaturated fatty acids. The data suggest that hydration of seed and pollen causes a release of free radicals from the trapped state.

1983. Lipid changes during natural aging of soybean seeds. -Physiol. Plant. 59: 467^70.When soybean seeds [Glycine max (L.) Merr. cv. Wayne] were stored at approximately 4°C and low humidity for 44 months ("natural aging") there was a marked decline in vigor and viability which was associated with a decrease in the proportion of the polyunsaturated fatty acids. Other lipid parameters showed little change. Seeds subjected to high humidity at 40°C for several days ("accelerated aging") experience a comparable decline in vigor and viability, but without the change in fatty acid polyunsaturation. These results indicate that accelerated aging may cause loss of vigor in a manner quite different from natural aging. The accelerated aging treatment is therefore of limited usefulness in investigations of the mechanism of natural seed aging.