Interconversion of gibberellin A20 to gibberellin A29 by etiolated seedlings and germinating seeds of dwarf Pisum sativum

Tritium labelled gibberellin A₂₀ ([³H]-GA₂₀) applied to etiolated shoots and germinating seeds of dwarf pea (Pisum sativum L. cv. Meteor) was converted to gibberellin A₂₉. Identifications were made by GLRC and GC-MS.     

Proteinase A-like enzyme from germinated kidney bean seeds. Its action on phaseolin and vicilin

A cysteine proteinase that possibly participates in the degradation of phaseolin, the main storage protein of kidney bean ( Phaseolus vulgaris L. cv. Moldavian) was isolated from germinating kidney bean seeds and partially characterized. According to its properties it may be classified as a member of a group of homologous cysteine proteinases A, also present in germinating seeds of a number of other plants. The proteinase of this group hydrolyze storage proteins to short peptides. Similarly, the kidney bean proteinase hydrolyzes vicilin, the reserve protein of vetch ( Vicia sativa ). However, its action on phaseolin is limited to the cleavage of subunits into two approximately equal parts and to the splitting off a small number of short peptides. An explanation of phaseolin resistance to the action of this proteinase is proposed on the basis of the differences of its structure from that of other homologous 7S proteins.     

Na2CO3胁迫下青海星星草种子萌发过程中淀粉酶活性等的变化

对Na2CO3胁迫下青海星星草种子萌发过程中淀粉酶活性、可溶性糖含量、呼吸强度的变化进行了研究。结果表明在Na2CO3胁迫下,种子萌发过程中淀粉酶活性、可溶性糖含量、呼吸强度与空白对照相比均下降,当Na2CO3浓度大于5.00%时,青海星星草种子在播种后至测量结束时,淀粉酶活性、可溶性糖含量、呼吸强度几乎都没有变化,三者与Na2CO3胁迫浓度的负相关关系均极其显著。在播种后的1～8d可溶性糖含量的变化与淀粉酶活性的变化基本趋于一致,两者呈显著的正相关关系。第8天以后,可溶性糖含量开始降低,而淀粉酶活性继续升高,说明可溶性糖已被利用、转化或合成新物质,Na2CO3胁迫下可溶性糖含量减少主要是因为淀粉酶活性受到了抑制。水解酶活性降低、储藏物质不能动员导致其不能水解、呼吸代谢受抑制是Na2CO3胁迫下青海星星草种子萌发受抑制的主要原因。     

The effect of kinetin on the level of an indoleacetylaspartic acid like substance in germinating seeds and young plants of Phaseolus vulgaris

Kinetin treatment increased the level of an extractable indoleacetyl conjugate, apparently indoleacetylaspartic acid (IAAsp) in germinating seeds and young plants of Phaseolus vulgaris L. cv. Alabaster. The level of this substance in extracts of treated seeds was always higher than that from water treated seeds irrespective of whether the seeds had been extracted 24, 48 or 72 h after the beginning of the treatment. In all parts of young bean plants treated with kinetin there was more of the substance than in the corresponding parts of water treated plants.     

Alterations in Endogenous Levels of Gibberellin-like Substances during Germination of Phaseolus vulgaris Seeds

The endogenous gibberellin-like substances were determined in mature dry and germinating bean seeds, Phaseolus vulgaris L. cv. Alabaster. Methanol extracts were partitioned against ethyl acetate and butanol at neutral and acid pH. Each phase was individually chromatographed on a silica gel column. The gibberellin activity was measured with the Tan-ginbozu dwarf rice micro-drop bioassay. Each extract was tested in two dilutions. Extracts from dry seeds showed the highest gibberellin activity, largely attributable to ethyl acetate-soluble substances. The activity was considerably reduced in extracts from seeds imbibed for 1 day. Gibberellin-like substances soluble in butanol appeared in extracts from seeds soaked for 1 or more days.     

不同含水量的豌豆种子萌发时物质动员及代谢研究

不同含水量的豌豆种子在饱和水蒸气中保持7d过程中,含水量低于萌动临界含水量时,子叶中贮藏蛋白质和淀粉的动员不能启动;含水量达到或超过萌动临界含水量,贮藏物质的动员被启动,豌启种子萌动后,子叶中蛋白质和淀动员程度与种子含水量呈正相关,前3d物质动员的程度比后4d强烈得多,因此,含水量是豌豆种子萌发时物质动员的启动因子和调节因子,同时,豌豆种子的含水量直接影响胚轴的生长状况。     

Generation of a membrane potential by electron transport in plasmalemma-enriched vesicles of cotton and radish

Plasmalemma-enriched vesicles were isolated from cotton roots (Gossypium hirsutum L. cv Acala San Jose 2) and from germinating radish seeds (Raphanus sativa L. cv Tondo Rosso Quarantino). When 100 millimolar ascorbate was added to the grinding medium, the addition of ferricyanide to either preparation led to an inside positive membrane potential as measured by the accumulation of thiocyanate. It is suggested that electrons from ascorbate were being transported electrogenically across the membrane to ferricyanide, resulting in an accumulation of protons within the vesicle. The redox activity of the vesicles has some similarities to that occurring in intact cells, thus providing a simpler system to study the components and effects of transmembrane electron transport.     

Effect of aflatoxin B1 on chlorophyll, nucleic acid and protein contents in maize

Aflatoxin B1 significantly lowered the contents of nucleic acids (DNA, RNA) and protein (both quantititive and qualitative) of germinating seeds of maize cv. Suwan Composite and also the contents of chlorophylls and carotenoids in seedlings. The extent of inhibition depended on the concentration of toxin. This revised version was published online in July 2006 with corrections to the Cover Date.     

Sugars and desiccation tolerance in seeds

Soluble sugars have been shown to protect liposomes and lobster microsomes from desiccation damage, and a protective role has been proposed for them in several anhydrous systems. We have studied the relationship between soluble sugar content and the loss of desiccation tolerance in the axes of germinating soybean (Glycine max L. Merr. cv Williams), pea (Pisum sativum L. cv Alaska), and corn (Zea mays L. cv Merit) axes. The loss of desiccation tolerance during imbibition was monitored by following the ability of seeds to germinate after desiccation following various periods of preimbibition and by following the rates of electrolyte leakage from dried, then rehydrated axes. Finally, we analyzed the soluble sugar contents of the axes throughout the transition from desiccation tolerance to intolerance. These analyses show that sucrose and larger oligosaccharides were consistently present during the tolerant stage, and that desiccation tolerance disappeared as the oligosaccharides were lost. The results support the idea that sucrose may serve as the principal agent of desiccation tolerance in these seeds, with the larger oligosaccharides serving to keep the sucrose from crystallizing.     

Activities of some peptidases and proteinases in germinating kidney bean, Phaseolus vulgaris

The activities of aminopeptidase (EC 3.4.11), dipeptidase (EC 3.4.13), carboxypeptidase (EC 3.4.16), naphthylamidase (EC 3.4.11) and proteinases (EC 3.4.21) were assayed in extracts from the cotyledons and the axial tissues of resting and germinating kidney beans ( Phaseolus vulgaris L. cv. Processor).
The activities of the alkaline peptidases (aminopeptidase hydrolyzing Leu-Tyr at pH 9.2 and dipeptidase acting on Ala-Gly at pH 8.5) and naphthylamidases (hydrolyzing Leu-β-naphthylamide at pH 6.4) were high in the cotyledons of resting seeds, but decreased during germination. This decrease was faster than the loss of the total nitrogen. On the contrary, the activities of carboxypeptidase (hydrolyzing carbobenzoxy-Phe-Ala at pH 5.9) and proteinases (acting on haemoglobin at pH 3.7 and on casein at pH 5.4 and 7.0) were low in the resting seeds, but increased during germination reaching their maximal values when the mobilization of nitrogen was highest. It has been suggested that the breakdown of storage proteins is initiated inside the protein bodies by acid proteinases and carboxypeptidases. Although the activities of the alkaline peptidases and naphthylamidases decreased during germination, these were still relatively high and enough for the completion of the proteolytic breakdown. Thus, it is suggested that, as a final step in a chain of events, the main role for the alkaline peptidases in the cotyledons of germinating seeds is to provide amino acids for the growth of the seedling.     

Gibberellins in seedlings and flowering trees of Prunus avium L

Extracts of acids from mature seeds, germinating seeds, first, second and third year seedlings as well as mature, flowering trees of sweet cherry (Prunus avium L. cv. Stella) were analysed by gas chromatography-mass spectrometry. The presence of the known gibberellins (GAs) GA1 (1), GA3 (4), GA5 (7), GA8 (11), GA19 (14), GA20 (12), GA29 (13), GA32 (5), GA85 (2), GA86 (3) and GA87 (6) was confirmed by comparison of their mass spectra and Kovats retention indices with those of standards or literature values. In addition, 16alpha,17-dihydrodihydroxy GA25 (16) was identified and its stereochemistry confirmed by rational synthesis. The 12alpha,13-dihydroxy GAs, GA32 (5), GA86 (2), GA86 (3) and GA87 (6), were detected in mature seeds, germinating seeds and young seedlings, but not in flowering plants. The 13-hydroxy GAs, GA1 (1) and GA3 (4), were present in germinating seeds and, in addition to these, GA5 (7), GA8 (11), GA19 (14), GA20 (12) and GA29 (13) were detected in seedlings and mature flowering plants. In germinating seeds and seedlings (while the plants were growing actively), concentrations of the 12alpha,13-dihydroxy GAs, measured by bioassay, declined and those of the 13-hydroxy GAs increased. The results are discussed with reference to the known and predicted effects of the GAs on the vegetative growth and flowering of P. avium plants.     

Gibberellin-like activity in cotyledons and embryonic axes during pea seed germination

Endogenous gibberellin-like activity was determined in dry pea seeds (Pisum sativum cv. Bördi), in cotyledons and axes of germinating pea seeds and also in excised cotyledons and axes. During the first two days of pea seed germination, neither the embryonic axes nor the cotyledons show a mutual influence on gibberellin activity, but this appears after 72–96 h of germination. The gibberellin-like activity m cotyledons and axes of germinating seeds increased during the same period, but it decreased in isolated axes and excised cotyledons.     

Evidence for osmotic regulation of hydrolytic enzyme production in germinating barley seeds

α-Amylase levels in intact seeds of barley (Hordeum vulgare L. cv. Himalaya) reach a maximum at 3 to 4 days of germination while gibberellin levels continue to increase beyond 6 days of germination. In contrast to its effect on half seeds, gibberellic acid does not increase the total amount of α-amylase produced in germinating seeds. The inability of gibberellic acid to stimulate α-amylase production is not related to its availability; rather, evidence suggests that a factor(s) in whole seeds prevents further enhancement of α-amylase formation and accumulation. Hydrolysis products accumulate in the subaleurone space of the endosperm of germinating seeds up to concentrations of 570 milliosmolar. Chromatography of these hydrolysis products indicate the presence of maltose and glucose. Calculations based on reducing sugar determinations show that glucose accounts for as much as 57% of the solutes present in the endosperm fluid. Both maltose and glucose in the range of 0.2 to 0.4 M effectively inhibit the production of α-amylase by isolated barley aleurone layers. This inhibition is quantitatively similar to that brought about by solutions of polyethylene glycol and mannitol. On the basis of these data we propose that hydrolysis products which accumulate in the starchy endosperm of germinating seeds function to regulate the production of hydrolytic enzymes by the aleurone layer.     

Reduced phytic Acid content does not have an adverse effect on germination of soybean seeds

Altering the level of phytic acid phosphorus by nutritional means had no effect on the ability of soybean (Glycine max L. [Merr.], cv `Williams 79') seeds to germinate under laboratory or greenhouse conditions. Dry matter moved out of the cotyledons at similar rates whether the germinating seeds initially contained low (0.19), medium (0.59), or high (1.00 milligram per seed) phytic acid phosphorus. Growth of roots and shoots from 3 to 9 days after planting was similar for seeds containing low and medium levels of phytic acid phosphorus. The medium level of phytic acid resembles that found in field-grown seed, so it is clear that soybean seeds normally contain a phosphorus reserve far above that needed for germination and early seedling growth.     

Control of the formation of amylases and proteases in the cotyledons of germinating peas

Protease activity increased in attached cotyledons of germinated peas (Pisum sativum L. cv. Alaska) as the stored proteins declined but did not increase in excised cotyledons incubated for the same length of time. Cotyledons of seeds germinated in the presence of a casein hydrolysate solution developed less protease activity than did those germinated on water. These results suggest that accumulation of amino acids regulates the protease level in the cotyledons of germinating peas.     

Changes in phytohormone contents in chickpea seeds germinating under lead or zinc stress

The present work describes the changes that take place in phytohormone contents in germinating chickpea (Cicer arietinum cv. Aziziye-94) seeds in response to heavy metal stress. For this aim, endogenous abscisic acid (ABA), gibberellic acid (GA₃), zeatin (Z) and zeatin riboside (ZR) contents were followed for 24, 48 and 72 h in chickpea seeds germinating at the concentrations of 0.1, 1.0 and 5.0 mM Pb or 0.1, 1.0 and 10 mM Zn. The results showed that Pb and Zn significantly delayed and impeded the germination of chickpea seeds. The negative effect of Pb on germination was higher than that of Zn. Further, Pb increased ABA and Z contents while decreased GA₃ content in the germinating seeds. The high concentrations of Zn (1.0 and 10 mM) decreased contents of Z, ZR and GA₃ while 0.1 mM Zn increased the content of the same hormones. The ABA content was enhanced by Zn in all concentrations used.     

Induction of Heat Shock Proteins and Acquisition of Thermotolerance in Germinating Pigeonpea Seeds

Heat shock proteins (HSPs) ranging in molecular masses from 14 to 110 kDa were induced in embryonic axes of germinating Cajanus cajan (L.) Millspaugh seeds after exposure to 40 °C for 1 or 2 h. At 45 °C, there was a marked decline in synthesis of HSPs. A close relationship was observed between HSPs induced and the growth of the germinating seeds. Pretreatment of germinating seeds at 40 °C for 1 h or 45 °C for 10 min followed by incubation at 28 °C for 3 h led to considerable thermotolerance (45 °C, 2 h) and the recovery of protein synthesis. This revised version was published online in July 2006 with corrections to the Cover Date.     

Excess boron reduces polyphenol oxidase activities in embryo and endosperm of maize seed during germination

The effects of increasing concentrations of boron (0, 0.1, 1, 10 and 20 mM) as boric acid on the rate of germination and polyphenol oxidase activities in embryo and endosperm tissues of maize seeds (Zea mays L. cv. Arifiye) were studied. The germination percentage of maize seeds was not affected by boron concentrations up to 10 mM, and decreased by 20 mM. Distilled water and lower boron concentrations (0.1 and 1 mM) increased polyphenol oxidase activities at the beginning of germination up to 12 h whereas its excess levels (10 and 20 mM) decreased polyphenol oxidase activities in embryos and endosperm during germination. Polyphenol oxidase activities with o-diphenolic substrates (caffeic acid, catechol and dopa) were found to be higher than with a monophenolic substrat (tyrosine) in both embryos and endosperms. Further, caffeic acid oxidizing polyphenol oxidase was found to show more activity in embryos of the seeds germinating in distilled water when compared to other substrates.     

Asparagine Enhances Starch Accumulation in Developing and Germinating Lupin Seeds

Regulation of starch accumulation in yellow (Lupinus luteus L.), white (L. albus L.), and Andean lupin (L. mutabilis Sweet) developing and germinating seeds was investigated. Research was conducted on cotyledons isolated from developing seeds as well as on organs of germinating seeds, that is, isolated embryo axes, excised cotyledons, and seedling axes and cotyledons. All organs were cultured in vitro for 96 h in different carbon (60 mM sucrose) and nitrogen (35 mM asparagine or 35 mM nitrate) conditions. Ultrastructure observation showed one common pattern of changes in the number and size of starch granules caused by sucrose, asparagine, and nitrate in both developing and germinating seeds. Sucrose increased the number and size of starch granules. Asparagine additionally increased starch accumulation (irrespective of sucrose nutrition) but nitrate had no effect on starch accumulation. Asparagine treatment resulted in a significant decrease in soluble sugar level in all organs of germinating lupin seeds of the three species investigated. The above-mentioned changes were most clearly visible in white lupin organs. In white lupin, starch granules were visible even in cells of sucrose-starved isolated embryo axes where advanced autophagy occurs. The importance of asparagine-increased starch content in the creation of a strong source–sink gradient in developing and germinating lupin seeds is discussed.     

Influence of Seed Pre-treatments with Plant Growth Regulators on Metabolic Alterations of Germinating Maize Embryos Under Stressing Temperature Regimes

The germination performance of maize seeds (Zea mays L. cv.Partap-1) pre-treated individually with the substituted phthalimideAC 94,377 (1-(3-chlorophthalimido)-cyclohexanecarboxamide),GA₄₊₇ and ABA was markedly improved under sub- and supra-optimaltemperature regimes. ABA was especially stimulatory at the sub-optimaltemperature. Metabolic alterations in the germinating embryosof treated seeds revealed an increased accumulation of solublesugars and proteins compared with the controls under stressingtemperatures. The activities of acid phosphatase, invertase,catalase and peroxidase were seemingly related to the alleviationmetabolism. It is suggested that gibberellins and abscisic acidmay have positive regulatory effects in triggering the systemfor stress alleviation. Germination, Zea mays, temperature, growth regulators, embryos, metabolism