In view of the finding that dry seeds may exist in the glassy state, a brief review of the commonest methods of detection and quantification of the glass transition is presented. While the glassy state may contribute to seed tolerance of desiccation, it does not appear to account for desiccation tolerance. Its major function in dry seeds may be its contribution to the stability of the seed components during storage.

A computer-aided comparison of tomato (Lycopersicon esculentum Mill.) seed protein patterns, obtained after two-dimensional gel electrophoresis, was made for three different extraction procedures: TCA acetone/lysis buffer, lysis buffer only and modified Laemmli/lysis buffer. Comparison of the isolation methods showed that about half of the amount of proteins detected was common in each method. Also, proteins specific to some isolation methods were detected. Protein synthesis during imbibition was monitored using 35S-methionine. After labelling the proteins were extracted using TCA acetone/lysis buffer. Following two-dimensional gel electrophoresis the gels were first silver stained, to give a general picture of all proteins present in the seed, then the gels were exposed to a film for autoradiography. Comparison of the in vivo-synthesized protein patterns and the silver-stained proteins revealed that from day 0 to day 1 the protein pattern was changed but the total number of different spots was similar. After 1 day of imbibition, the number of protein spots increased greatly and the protein pattern changed again.

Seeds from an assortment of 28 grass species (including two cereals), chiefly representing different tribes of the sub-family Pooideae were tested for the presence of BASI-like proteins using Western blotting techniques and antisera raised against the barley amylase/subtilisin inhibitor. A single protein species of the same molecular weight as the BASI protein was detected in each member of the tribes Triticeae and Bromeae tested. Members of the Triticeae and Bromeae were the only species to produce high pi α-amylase isoenzymes following germination of the grain in addition to low pl forms which were present in all species tested. Anti-BASI antibody binding patterns for the other grasses examined were variable with the strongest staining being observed for Lolium species. In these species, either a double or single protein band fractionally larger than the BASI protein was recognized. In most other cases antibody binding was barely or not detectable. Inhibitor preparations from Hordeum vulgare and Lolium perenne were effective at inhibiting wheat α-amylase but neither had any effect against enzyme produced by germinating L. perenne.

Wheat seed lots of different viability were obtained by an accelerated ageing technique in which seeds were hydrated up to 12.5–14.5% on a fresh weight basis and stored at 35°C. Ageing was accompanied by a progressive delay of the onset of germination and a decrease of [35S]-methionine uptake and incorporation into soluble proteins of the imbibing embryos. A detailed analysis of newly synthesized proteins by two-dimensional polyacrylamide gel electrophoresis showed that normal protein patterns during the germination process were impaired by ageing. Only two groups of polypeptides with molecular masses of 84.9–69.5 and 66.6–60.2 kDa, respectively, were actively produced while most proteins decreased or were definitely degraded. Our results suggest that the biochemical changes required for germination are gradually opposed by a deterioration process and that some newly-synthesized polypeptides can be taken as markers in assessing seed survival of ageing stress.

Relationships have been investigated between gene transcript abundance, enzyme activities and storage product accumulation in developing maize (Zea mays L.) kernels from 10 to 55 days postpollination (DPP). At the early stages of kernel development, there was very little increase in dry weight but kernels accumulated high concentrations of sugars and amino acids. At the end of this ‘lag’ phase (at 15 DPP), many transcripts appeared with little evidence of their translation. The initiation of the kernel-fill period at 20 DPP was characterized by a sudden rise in total RNA, increases in enzyme activities, and the initiation of storage product accumulation. Zein accumulation during this phase was highly correlated with α-zein transcript abundance. Starch accumulation was correlated with both the activity of ADP-GIc pyrophosphorylase and the abundance of gene transcripts encoding this enzyme (Shrunken-2 and Brittle-2). DNA content of kernels increased linearly up to 30 DPP as a result of endoreplication, but had no apparent relationship to gene expression. DNA may accumulate as a storage product. Kernel-fill terminated when the moisture content fell below 36% and was marked by a decline of transcripts and a reduction of enzyme activities.

During a 7-day conditioning treatment of clumps of oil palm (Elaeis guineensis Jacq.) somatic embryos on a medium containing 0.75 M sucrose, the fructose and glucose concentrations remained constant, whereas a ten-fold and twenty-fold increase were noted for sucrose and starch concentrations, respectively. The only new sugar detected was arabinose which remained at a low concentration. After conditioning on media supplemented with various sugars and polyols at similar osmolarities, recovery of clumps of embryo growth was satisfactory except with ribose. After an additional desiccation period, survival was optimal with fructose, galactose, sucrose and glucose, intermediate with maltose and lower with other compounds. When embryos were cryopreserved without previous desiccation, survival was noted after conditioning treatment with sucrose only. In contrast, when freezing was performed after dehydration, survival could be obtained with several substances. It was optimal with sucrose, fructose, galactose and raffinose but was possible also with sorbitol and glucose. Intensity of recovery of proliferation was highest with embryos conditioned with sucrose.

Quercus robur L. fruits are desiccation sensitive and shed from the plant at high moisture content (c. 48%). Water relations measurements were taken at intervals during the germination of prematurely-harvested immature fruits and naturally-shed mature fruits. In fruits from both harvests the pericarp and seed coat delayed germination by providing physical barriers to emergence of the radicle and by restricting the rate of imbibition. Although immature fruits could germinate in the absence of water they germinated more rapidly in the presence of an external water supply. The fully-mature fruit required a supply of external water, but germination was more rapid than in immature fruits. Substantial physiological changes, resulting in the accumulation of solutes, and increased axis size and extensibility occurred before splitting of the pericarp and subsequent germination of immature fruits. Such changes did not occur in fully-mature fruits, but fruits, from both harvests imbibed water and splitting of the pericarp appeared to result from increased embryo size and tissue pressure. Splitting was minimal prior to germination in immature fruits without an external water supply. It is suggested that the resulting reduction in Ψp when the pericarp splits was greater in the axis than in the cotyledons because of its greater capacity for expansion. This would create a Ψw gradient driving water flow to the axis from the cotyledons allowing continued radicle growth for germination.

Hydration-dehydration seed pretreatments are well-known to improve germination rate, germination and vigour. However, contradictory results have been reported concerning the effect of a pretreatment on longevity. The present paper shows that the effect of a seed pretreatment on longevity is largely dependent on the quality of the seed at the time of pretreatment. Pretreating wheat seeds of high quality increased the rate of viability loss during subsequent storage. On the other hand, pretreating wheat seeds of relatively low quality decreased the rate of seed deterioration during subsequent storage. In the light of these findings, hitherto contradictory results in the literature could be explained.

Wheat which was grown in acid-washed sand and irrigated with a molybdenum-free nutrient solution was treated with various concentrations of molybdenum (Mo) as a foliar spray at the flag leaf stage. At maturity, dormancy levels and abscisic acid (ABA) content of the seed were determined. Seed dormancy and ABA content increased with increasing rates of Mo application. In a field experiment, wheat (cv. SST 66) was treated with 100 ppm Mo by foliar application at the flag leaf stage. Embryos were tested for sensitivity to exogenously applied ABA. Embryos from Mo-treated plants showed enhanced sensitivity to ABA-induced inhibition of germination. The Mo application also resulted in significantly higher levels of endogenous ABA and Mo in the seeds. It is postulated that Mo deficiency leads to a lack of dormancy in wheat via reduced synthesis of ABA.

A survey of proteinaceous inhibitors of the serine proteinases, bovine trypsin and chymotrypsin, that are extractable from dry seeds of several cultivars of pasture grasses has been undertaken. Using crude extracts, most cultivars screened contained inhibitors of chymotrypsin, whereas trypsin inhibition was not detectable. Seeds from four cultivars, Lolium perenne L. cv. Grasslands Ruanui, Lolium × boucheanum cv. Grasslands Greenstone, Festuca arundinacea Schreb. cultivars Grasslands Roa and Grasslands Garland, that contained more potent chymotrypsin inhibition were purified further. After gel filtration chromatography, both trypsin and chymotrypsin inhibition could be observed in all four cultivars, and each separated into two discrete native molecular weights; one of ca. 20–22 kDa and one of ca. 8–10 kDa. However, activity staining, after polyacrylamide gel electrophoresis, revealed an array of iso-inhibitors with molecular weights that ranged from ca. 3 kDa to 20 kDa. One of these, a dual trypsin/chymotrypsin inhibitor of ca. 12 kDa that is present in all four cultivars examined, was purified to homogeneity from F. arundinacea cv. Grasslands Garland using anhydro-trypsin affinity chromatography and reverse-phase HPLC. The protein was found to comprise two closely related peptides and N-terminal amino acid sequencing revealed highest identity with a trypsin inhibitor identified in rye (Secale cereale) seeds.

Evidence is provided to show that frozen, hydrated seeds and seed tissues can be observed by low temperature field emission scanning electron microscopy. This technique allows preparation and observation of seed samples that contain 13–60% water without altering their moisture content. The technique provides information about the surface structure of seeds and also allows specimens to be fractured to reveal internal features of tissues. Futhermore, both halves of fractured specimens can be retained, examined and photographed either as two-dimensional micrographs or as stereo pairs when three-dimensional observation (stereology) or quantitative measurements (stereometry) are desired. Use of this technique avoids artefacts associated with chemical fixation, dehydration, and critical point drying—procedures that are usually required to prepare seed tissues for scanning electron microscope examination. This technique does not affect the degree of hydration in specimens; it can be used to localize water in tissues to determine their degree of hydration. This technique should find wide application in developmental studies of seeds, especially during maturation, imbibition and germination.