The Survival of Germinating Orthodox Seeds after Desiccation and Hermetic Storage

Seeds of barley (Hordeum vulgare L.) and mung bean (Vigna radiata(L.) Wilczek), with orthodox seed storage behaviour, were imbibedfor between 8 h and 96 h at 15 °C and 25 °C, respectively,while barley seeds were also maintained in moist aerated storageat 15 °C for 14 d. These seeds and seedlings, together withcontrols, were then dried to various moisture contents between3% and 16% (wet basis) and hermetically stored for six monthsat —20°C, 0°C or 15°C. In both species, neitherdesiccation nor subsequent hermetic storage of the control lotsresulted in loss in viability. The results for barley seedsimbibed for 24 h were similar to the control, but desiccationsensitivity increased progressively with duration of imbibitionbeyond 24 h in barley or 8 h in mung bean; these treatmentsalso reduced the longevity of the surviving seeds in air-drystorage. Loss in viability in barley imbibed for 48 h was mostrapid at the two extreme seed storage moisture contents of 3·6%and 14·3%, and in both these cases was more rapid at15 °C than at cooler temperatures. Similarly, for mung beanimbibed for 8 h, loss in viability was most rapid at the lowest(4·3%) moisture content, but in this case it was morerapid at –20 °C than at warmer temperatures. Thus,these results for the storage of previously imbibed orthodoxseeds conform with the main features of intermediate seed storagebehaviour Key words: Barley, Hordeum vulgare L., mung bean, Vigna radiata (L.) Wilczek, desiccation sensitivity, seed longevity, seed storage behaviour     

Proteins of Axial Organs of Dormant and Germinating Horse Chestnut Seeds: 1. General Characterization

This is the first characterization of proteins from axial organs of recalcitrant horse chestnut seeds during deep dormancy, dormancy release, and germination. We demonstrated that, during the entire period of cold stratification, axial organs were enriched in easily soluble albumin-like proteins and almost devoid of globulins. About 80% of the total protein was found in the cytosol. Approximately one third of cytosolic proteins were heat-stable polypeptides, which were major components of total proteins. Heat-stable proteins comprised three groups of polypeptides with mol wts of 52–54, 24–25, and 6–12 kD with a predominance of low-molecular-weight proteins. The polypeptide patterns of heat-stable and thermolabile proteins differed strikingly. Heat-stable proteins accumulated in axes during the late seed maturation, comprising more than 30% of the total protein in axes of mature seeds. The polypeptide patterns of the total protein of axial organs and its particular fractions did not change in the course of seed dormancy and release. At early germination, the content of heat-stable proteins in axes decreased and their polypeptide pattern changed both in the cytosol and cell structures. We believe that at least some heat-stable proteins can function as storage proteins in the axes. Localization of storage proteins in the cells of axial organs and the role of heat-stable proteins in recalcitrant seeds are discussed.     

Starch Degradation Metabolism towards Sucrose Synthesis in Germinating Araucaria araucana Seeds

As starch is the main seed reserve material in both species of Araucaria of South America, A. araucana and A. angustifolia, it is important to understand starch breakdown in both embryo and megagametophyte tissues of Araucaria seeds. Sugar analysis by thin layer chromatography indicates that sucrose is the main sugar produced in both tissues. Enzyme reactions coupled to benzidine oxidation indicate that sucrose is the main sugar moved from the megagametophyte to the growing regions of the embryo via the cotyledons.

Phosphorylase was detected in both embryo and megagametophyte tissues by the formation of [³²P]glucose-1-P and by formation of [¹⁴C] amylopectin from [¹⁴C]glucose-1-P. The enzyme activity increases 5-fold in both embryo and gametophyte to a peak 18 hours after the start of imbibition. Debranching enzyme, α-glucosidase, and hexokinase are also present in both embryonic and megagametophytic tissues.

Branched glucan oligosaccharides accumulate during this time, reaching a maximum 40 hours after imbibition starts, and decline after germination occurs.

The pattern of activity of the enzymes studied in this work suggests that starch degradation is initiated by α-amylase and phosphorylase in the embryo and by phosphorylase mainly in the megagametophyte. Sucrose-P synthase seems to be the enzyme responsible for sucrose synthesis in both tissues.

     

Synthesis of DNA and the Development of Amylase and Phosphatase Activities in Cotyledons of Germinating Seeds of Vaccaria pyramidata

As in cotyledons of Agrostemma githago, synthesis of DNA takesplace after germination in cotyledons of Vaccaria pyramidataand is followed by the formation of hydrolases, in particular,-amylase and acid phosphatase. If DNA synthesis is inhibitedby hydroxyurea, no, or only slight, enzyme activity develops.The possible role of this DNA synthesis is discussed. Key words: DNA synthesis, amylase activity, phosphatase activity, seed germination, cotyledons, Vaccaria pyramidata     

Oxidative Phosphorylation in Germinating Lettuce Seeds

The effect of thiourea and coumarin, in vivo and in vitro, onthe phosphorylating activity of lettuce mitochondria was investigated,as well as the effect of coumarin on the P/O ratio. It was shownthat both substances in vitro inhibit phosphorylation; whilein vivo coumarin inhibits but thiourea under certain circumstancesstimulates. Coumarin was also shown to decrease the P/O ratioand therefore may be considered as an uncoupler. The difficulties in considering these effects of the substancesas a primary mechanism controlling germination are pointed outand discussed.     

The Relation of Storage Protein to Vigor and Its Mobilization Pattern in Germinating Peanut Seeds

The peanut (Arachis hypogaea L.) seeds harvested at the last stage of maturation were divided into five grades by size. The content of total protein, salt-soluble protein, arachin, conarachin I and 2s globulin in these seeds were measured. No obvious differences in germination percentage and the length of radicle and hypocotyl within 3d germination in dark were observed among the five grades of seeds. But there were significant differences in the seedling growth after two weeks of germination in light. There was a very close correlation between the storage protein in cotyledons and the seedling growth. When seeds germinated in light, the efficiency of mobilization of the salt-soluble protein in the cotyledons was higher than that in the cotyledons of the seeds germinating in dark. All of the salt-soluble protein in cotyledons was used up after 14d seedling growth in light. SDS-PAGE of salt-soluble protein showed that 23.5, 38.5 and 41 kD subunits of arachin were first mobilized during germination. The 18 kD subunits of arachin were not mobilized until the above-mentioned subunits were used up. The 60.5 kD subunit of conarachin I and 2s globulin were degradated within 2 to 3 days during germination.     

Synthesis and Posttranslational Activation of Sulfhydryl-Endopeptidase in Cotyledons of Germinating Vigna mungo Seeds

A sulfhydryl-endopeptidase was purified as a 33 kilodalton (kD) mass polypeptide from cotyledons of Vigna mungo seedlings. Immunoblot analysis with antiserum made against the purified enzyme showed that the sulfhydryl-endopeptidase was synthesized only in the cotyledons during germination and that the amount of the enzyme increased until 4 days after imbibition and decreased thereafter. Next, an RNA fraction was prepared from cotyledons of 3 day old seedlings and translated in a wheat germ system. The synthesis of a 45 kD polypeptide was shown by the analysis of its translation products by immunoprecipitation with the antiserum to the endopeptidase and gel electrophoresis. When the RNA fraction was translated in the presence of canine microsomal membranes, a smaller polypeptide, having a 43 kD molecular mass, was detected as the translation product. When membrane-bound polysomes, but not free polysomes, prepared from cotyledons were used for translation in the wheat germ system, both the 43 and 45 kD polypeptides were synthesized. By incubation of a crude enzyme extract from cotyledons at 5 ± 1°C at neutral pH, the 43 kD polypeptide was sequentially cleaved to the 33 kD polypeptide via 39 and 36 kD intermediate polypeptides. The endopeptidase was activated simultaneously with the processing. Two-dimensional polyacrylamide gel electrophoresis showed that the 33 kD polypeptide was the fully activated form of the enzyme, whereas little or no activity was detected in other forms. From the present results, we postulate that the sulfhydryl-endopeptidase is first synthesized as the 45 kD precursor with a 2 kD signal peptide being cleaved, and that the 43 kD polypeptide is further cleaved to give the 33kD mature enzyme.     

萌发大麦种子水溶性蛋白组分提取

采用二次回归正交旋转组合试验方法,对大麦种子中水溶性蛋白组分的提取工艺进行了研究,得出了大麦种子水溶蛋白组分提取量与料液浓度,浸提温度和浸提时间的数学模型,确定了大麦籽粒水溶蛋白组分最佳提取条件为料液浓度9．1％,浸提温度20℃,浸提时间3h;通过连续检测萌发大麦种子水溶蛋白含量发现：随萌发时间增长,蛋白含量逐渐升高,麦芽中水溶蛋白含量约为大麦的4倍．     

Stronium Mobility in Germinating Seeds and Plants

The uptake of strontium in the bean plant (Phaseolus vulgaris) was linear for the first 34 hr during continuous exposure to radiostrontium. After 35 hr there was a sharp increase in the rate of uptake to 48 hr. Radioactivity could be detected in the plant as early as 1 hr after addition of radiostrontium to the growth medium.     

Ion Transport in the Testa of Germinating Seeds

Levengood, W. C. 1985, Ion transport in the testa of germinatingseeds.—J. exp. Bot. 36: 1053–1063. The current flow produced when an electrical potential is appliedto a partially hydrated seed is drastically altered by the applicationof a thermal pulse. Specific responses to thermally inducedchanges in electrical activity are related to the cell wallstructure of the seed coat and its state of hydration. It issuggested that expansion and contraction of the micropores inthe cell wall matrix provide a model based on a diffusion anddehydration during a thermal pulse and an ion-gating effectimmediately following the pulse. Mechanical flexing producedoscillatory behaviour in the electrical current flow throughseed coat tissues in a manner predicted by the thermal responses. Key words: Ion transport, testa, germinating seeds     

Regulation of De-N-Glycosylation Enzymes in Germinating Radish Seeds

The activities of the de-N-glycosylation enzymes endo-N-acetyl- [beta]-D-glucosaminidase (ENGase; EC 3.2.1.96) and peptide-N4- (N-acetyl-[beta]-D-glucosaminyl) asparagine amidase (PNGase; EC 3.5.1.52) were monitored during germination and postgerminative development in radish (Raphanus sativus L. cv Flamboyant). The ENGase activity was detected only during postgermination, whereas the PNGase activity was present at high levels in both stages. When germination was inhibited with abscisic acid or cycloheximide, PNGase activity was detected at a basic level and ENGase activity was not detected at all. PNGase is present as an active protein in dry seeds and is apparently synthesized during seed formation. Conversely, the absence of ENGase in dry seeds suggests that its activity is dependent on the protein synthesis that occurs during and after germination. Treatment with gibberellic acid confirmed the production of both de-N-glycosylation enzymes after germination, and demonstrated a temporal delay between the production of the two enzymes during this period. Our results suggest that the two de-N-glycosylation enzymes are differentially regulated during plant development.     

The Biosynthesis of Cytokinins in Germinating Lupin Seeds

Imbibed intact seeds, and excised embryos and cotyledons ofyellow lupin (Lupinus luteus L. cv. Weiko III) have been incubatedwith [¹⁴C]-adenine to investigate cytokinin biosynthesis duringthe early stages of germination. Following incubation the tissueswere extracted and purified by solvent partition and chromatographyon cellulose phosphate, diethylaminoethyl cellulose and SephadexLH-20 columns. Using a variety of thin layer chromatographic,high performance liquid chromato-graphic and chemical procedures,incorporation of ¹⁴C into dihydrozeatin riboside and its nucleotidewas demonstrated in extracts of intact embryos, intact cotyledonsand excised embryos. However, radioactivity was not found associatedwith cytokinins in fractions derived from the isolated cotyledons.This is the first direct demonstration of cytokinin biosynthesisin germinating seeds and the results indicate that the capacityfor cytokinin biosynthesis is probably confined to the embryonicaxes. If this is so, the levels of [¹⁴CJ-dihydrozeatin ribosideassociated with intact embryo and intact cotyledon fractionsindicate that the synthesized cytokinin is transported to andaccumulates in the cotyledons. Key words: Lupinus luteus, cytokinin biosynthesis, seed germination     

The Movement of Calcium in Germinating Pea Seeds

Pea seeds contain less calcium than phosphorus, potassium ormagnesium; more than half of this calcium is located in thetesta. Peas at either end of a pod have more calcium than thosein the middle. When pea seeds are allowed to germinate in water,less than 30 per cent of the cotyledonary calcium moved to thegrowing axis during the first 15 days of germination, whereas70–90 per cent of magnesium, potassium and phosphate wasexported. Various attempts to increase the amount of calciumexported were not successful. When radioactive calcium was appliedto the cotyledons, essentially no movement to the axis was observedunder conditions where extensive movement of radioactive phosphateoccurred.     

Apparent Free Space of Germinating Pea Seeds

The apparent free space (AFS) of pea seeds was determined by measurement of the exodiffusion of solutes from the seeds previously equilibrated with radioactive solutions. AFS (per cent of volume of water taken up by dry seeds) varied with the kinds of solutes used, that is, values of 27–30% were obtained for mannitol or leucine and 12% for malonate, at pH 6. When the seeds were incubated in a radioactive solution at lower pH (3.5), higher AFS values were obtained, especially for malonate. The AFS of imbibing seeds showed a tendency to increase during the course of imbibition.