Dehydrin and QP47, proteins present in mature pea seeds (Pisum sativum), have been proposed to play protective roles during desiccation. To identify possible relationships between these proteins and desiccation tolerance, their tissue locations and patterns of synthesis and degradation have been examined during germination. Tissue locations were determined by immunocytochemistry using polyclonal antibodies raised against a conserved dehydrin amino acid sequence and against purified QP47. In embryonic axis and cotyledon cells, QP47 and dehydrin were distributed uniformly with no apparent nuclear or organellar specificity. Both proteins were present in 24 h-imbibed axes that had not initiated radicle growth but were completely absent from 24 h-imbibed axes that had begun to grow. The amounts of QP47 and dehydrin in embryonic axes decreased with time after the start of imbibition and were undetectable by 48 h. When germination was prevented by polyethylene glycol (PEG) or abscisic acid (ABA), both proteins remained at their original amounts. Thus, both QP47 and dehydrin disappeared coincidently with the beginning of growth and not simply as a function of the time after imbibition. QP47 persisted in cotyledons until at least 31 days into seedling growth, whereas dehydrin was not detectable in cotyledons after 7 days. Dehydrin, but not QP47, could be re-induced in pea shoots and cotyledons by dehydration. The timing of degradation of both proteins was correlated with the loss of desiccation tolerance during germination of pea axes.

After 110 years of hermetic sealed storage at temperatures between 10 and 15°C and at a moisture content of 3.12%, Hordeum vulgare showed 90% germination and Avena sativa 81%. In addition, some seeds of Agrostemma githago, Lolium temulentum, Sinapis alba, Sinapis arvensis, and Vaccaria hispanica were still capable of germinating. This demonstrates that ultra-dry, long-term seed storage under ambient temperature conditions can successfully be achieved with the intention of cutting down risks and costs in germplasm conservation.

Excised axes from cotton (Gossypium hirsutum L. cv. M-8, a double haploid) were imbibed in vitro for 3,6,9,12,18 and 24 h. Data for length, fresh and dry weight and percentage water showed that excised axes undergo a triphasic pattern of growth: an initial burst, a short lag phase and then protracted rapid growth. Analysis of protein content with SDS-PAGE, and of activities of amino-, carboxy- and endopeptidases provided data indicating a direct correlation between major axis elongation growth between 12 and 24 h and enzymatic breakdown of storage proteins (especially those of 48 kDa) by carboxy- and endopeptidase. Data for axes imbibed at 30°C and 0–5°C for 12, 18 and 24 h indicated that a reduction in length and percentage moisture in the cold occurred in parallel with reductions in carboxy- and endopeptidase activities but not in ami-nopeptidase activity. The tentative conclusion is that carboxy- and endopeptidase are probably synthesized de novo in the axis during imbibition and are important in initial breakdown of storage proteins for axial elongation growth.

There is a carboxypeptidase in mung bean seeds that is localized in the protein bodies, the same vacuoles in which seed storage proteins are sequestered. This carboxypeptidase, called carboxypeptidase I (or Cpase I) has been purified by a series of ion-exchange and gel filtration columns. The pure enzyme consists of a single polypeptide chain with a MW of 41700 by SDS-PAGE or 42000 by size-exclusion HPLC. It has a pl of 4.36 and is a serine carboxypeptidase as shown by its inactivation by phenylmethylsulfonyl fluoride, and its resistance to other proteolytic inhibitory reagents. A survey of its activity with Cbz-dipeptides shows preference for C-terminal amino acids that are large, hydrophobic residues, and a small aliphatic amino acid such as alanine, but not glycine, at the penultimate amino acid residue. Cpase I can convert a trypsin inhibitor of the mung bean to its proteolytic intermediate lacking four amino acid residues at its C-terminus. This proteolytic intermediate is detected in the mung bean cotyledons during early growth. Levels of both the activity and immunological cross-reacting forms of this enzyme start high and decrease during early growth.

Benzyladenine, a synthetic cytokinin, stimulates DNA metabolism during maize germination; apparently such stimulation occurs in two phases, and during the first phase stimulations of DNA synthesis, of protein kinase activity (both α-amanitin repressible), of DNA polymerase and poly ADP-ribosyl polymerase activities are observed. Since the evidence suggested that the effects produced by BA were due, at least partially, to transcriptional activation, attempts were made to discover genes, by subtractive hybridization of a cDNA library or by differential display, whose expression depended on the presence of BA; however these were unsuccessful. BA modulated the expression of a limited number of genes only. The possible mechanism by which BA could be promoting DNA metabolism during maize germination is discussed.

Dormant weed seeds were germinated at constant and alternating temperatures using five chemicals. Germination of Chenopodium album when expressed in normal equivalent deviates, increased linearly with the logarithm of chemical dose up to an optimal concentration. Ethephon (2-chloroethyl phosphonic acid) and sodium azide slightly stimulated germination of C. album seeds at 20°C while potassium nitrate, thiourea and azide each interacted positively with alternating temperatures (5°/25°C). Relief of Avena fatua dormancy by azide exhibited a positive interaction with cool constant temperatures (3–10°C), and chemicals had smaller or no effects at higher and alternating temperatures. No chemical mixture, including that of nitrate, thlourea, ethephon, azide and hydrogen peroxide, promoted more germination than azide on its own in A. fatua or nitrate together with ethephon in C. album. In C. album, this result arose largely because nitrate and azide antagonized each other in the presence of ethephon. Peroxide and thiourea together relieved this antagonism so that the fourth order interaction was positive. The negative interaction of nitrate, azide and ethephon in C. album was avoided in a sequential treatment with nitrate plus ethephon for seven days followed by sodium azide. Relief of dormancy by nitrate and ethephon was optimized at 67 mM nitrate with 1.4 mM ethephon for C. album at 20°C and 20 mM nitrate with 1.4 mM ethephon for A. fatua at 15°C. None of the chemicals used in this investigation stimulated the germination of Rumex crispus seeds. The results are discussed with respect to chemical control of soil seed banks.