Changes in polyamines and related enzymes with loss of viability in rice seeds

Putrescine, spermidine and spermine of high vigour, low vigour and non-viable (classes 1, 2 and 3 respectively) seeds of Oryza sativa increased with loss of viability. The largest concentration of spermine was found in non-viable embryos. Spermine was absent in the husks of all the three categories of seeds. Arginine decarboxylase was greatest in high vigoured seeds and its activity gradually declined with loss of viability. However, diamine oxidase and polyamine oxidase activities gradually increased with the loss of viability of the seeds while DNA, RNA and protein contents decreased. The total content of polyamines increased on kinetin treatment but declined on ABA treatment. DNA, RNA and protein followed the same trend as polyamines. The polyamine contents increased by ca 3- and 4-fold, respectively, in high vigoured and low vigoured seeds on 10^?4 M kinetin treatment. The activity of ADC followed the same change as that of the polyamines in both cases, but the reverse was observed for the activities of diamine and polyamine oxidases.     

Seed Viability Determinations in Cabbage Utilizing Sinapine Leakage and Electrical Conductivity Measurements

A need exists for the development of rapid seed quality teststhat determine viability (defined as the ability to germinate)without the necessity for completion of germination. In cabbage(Brassica oleracea var. capitata L.) the compound sinapine,a choline ester of sinapic acid, has been shown to leak fromheat-killed (HK.) but not from viable seeds. Sinapine leakagewas studied as a more accurate method for identifying viableseeds than the conductivity test. After an 8 h soak, a 26-folddifference in sinapine leakage was detected between HK and viableseeds (as measured by the absorbance at 388 nm at pH 12) comparedto a 4-fold difference measured by electrolyte leakage. Theremainder of the studies were conducted on two seedlots of thesame cultivar. Viability was predicted on the same seed by assessingleakage from individual seeds into the soak water using threemethods; soak water colour, absorbance at 388 nm, and electricalconductivity. This information was compared with the actualgermination of each seed for the two seedlots. For both seedlots,the presence of sinapine in seed soak water (detected eitherby a yellow solution colour at high pH or by high absorbance),identified more seeds that were non-viable than the partitioncoefficient calculated from conductivity measurements (76%,72% and 28% of non-viable seeds were identified, respectively).It is proposed that leakage of sinapine is a better predictorof cabbage seed viability than electrical conductivity. Key words: Seed deterioration, seed leakage, germination prediction     

Crossing experiments within theCampanula dichotoma group (Campanulaceae)

Four supposedly closely related taxa were crossed artificially to test for hybridization barriers. Intra- as well as inter-specific crossings were made. The intra-specific crossings resulted in a high portion of viable hybrids, whereas hybridization barriers were found in all inter-specific combinations except one. The hybrids were non-viable at different levels, viz., (1) no seeds germinated, (2) seeds formed lethal chlorotic seedings, or (3) seeds formed chlorophyllous seedlings which survived the cotyledonary stage, but developed into intermediate forms with low pollen production and/or a strongly reduced pollen viability. Crossings betweenCampanula afra and any of the other three taxa resulted in a non-viable progeny. The crossing capacity amongC. occidentalis, C. kremeri, andC. dichotoma varied. Combinations with large-flowered maternal taxa and small-flowered paternal ones usually failed, whereas a high number of the reciprocal crossings produced hybrids which survived the cotyledonary stage. The hybrid plants varied in pollen viability and pollen production, however. It is concluded that theCampanula dichotoma group should be treated as comprising four distinct species.     

Free radical generation in Pinus sylvestris and Larix decidua seeds primed with polyethylene glycol or potassium salt solutions.

Electron paramagnetic resonance (EPR) spectra of Pinus sylvestris and Larix decidua seeds show that priming with PEG+200 mg kg(-1) gibberelic acid (GA(3)) results in appreciably higher free radical contents than in unprimed control samples. Only relatively minor changes in the free radical levels were observed in seeds primed with K(+) salts. However, both priming treatments have been reported previously to result in faster germination rates compared to controls without changing the germination percentage. In measurements on individual seeds of L. decidua, there were no significant differences between the mean free radical levels in viable and non-viable seeds within each treatment group. Thus, the elevation in free radical levels in the PEG+GA(3) treatments appear to be a direct consequence of the priming treatment and do not correspond to the initiation of germination.     

Germination and Food Reserves in Bambarra Groundnut Seeds (Voandzeia subterranea Thouars) after Different Periods of Storage

Studies were made on bambarranut seeds (Voandzeia subterraneaThouars) after 0, 6, 12, 18 and 24 months of storage in gunnybags under laboratory conditions (25–35 °C). Seeddeterioration during storage was indicated by delayed germination,reduced germinability, reduced growth of seedlings and increasednumber of stunted seedlings culminating in a total failure ofgermination after two years. Slight depletion of food reserves occurred during seed storage.The loss in fat was higher than starch or protein. Total solublesugars decreased while the content of total fatty acids andamino acids and soluble protein increased. Total nitrogen (N)remained unaffected while soluble-N and amino-N increased. Allthese components showed a rapid change (increase or decrease)from 12 months to 18 months of storage which was associatedwith commencement of rapid decline in germinability of the seedsand growth of the seedlings. Initial rapid imbibition of water was observed in viable aswell as non-viable seeds, though at a higher rate in the latterand followed by a lag period in both. At the end of 24 h ofimbibition, water content in non-viable seeds was less thanthat in viable ones. Key words: Voandzeia subterranea, Seed germination, Seed storage     

Ultrastructural changes in naturally aged Pinus pinea seeds

The decline of germination observed after storage of Pinus pinea L. seeds up to 35 years at room temperature was accompanied by an increase in their ability to leak reducing sugars, probably as a consequence of membrane alterations due to senescence. Results of studies of the cell ultrastructure of viable and non-viable seeds before and after imbibition indicate that such is the case. Noticeable changes occurred in the ultrastructure of endosperm and embryo cells with germinability loss, even in the unimbibed condition. The main alterations were spherosome coalescence, plasmalemma separation from the cell wall and chromatin aggregation.     

Protein metabolism during natural ageing in desiccating recalcitrant seeds of Shorea robusta

Seeds of Shorea robusta (sal) are recalcitrant owing to its high desiccation sensitivity. Germinability in sal seed was lost rapidly from 100 to 0 % within 8 days. Protein oxidation examined separately in axis and cotyledon of ageing sal seeds by monitoring the levels of carbonyls, hydroperoxide, malondialdehyde and 4-hydroxy-2-nonenal adducts with protein, Amadori and Maillard reaction products. Changes in protease and proteasome activity were also estimated. The levels of all the modified proteins and activities of protease and proteasome were similar in axis and cotyledons. The amounts of carbonyls (5.5 fold in axis and 3.9 fold in cotyledons) and hydroperoxides (13.5 fold in axis and 12 fold in cotyledons) increased significantly as the seeds became non-viable. Similarly, the levels of malondialdehyde and 4-hydroxy-2-nonenal adducts promoted as the storage period advanced and reached tenfold both in the axis and cotyledons in non-viable seeds. The ageing also promoted levels of reducing sugar along with rapid enhancement in the levels of Amadori and Maillard reaction products, respectively, by 4.4 and 1.8 fold in 5 days sal seeds. Substantial promotion in protease activity both in the axis (sevenfold) and cotyledons (tenfold) of absolutely aged seeds was discernible. The activity of proteasome exhibited steady decline from 0.767 to 0.170 nmol min^?1 g^?1 DM in axis and 0.20–0.086 nmol min^?1 g^?1 DM in cotyledons of ageing sal seeds. Changes in the ROS and protein catabolism/oxidation have been discussed to establish loss of germinability in desiccating recalcitrant sal seeds.     

Seed Maturation in Soybeans (Glycine max L. Merr.) is Independent of Seed Mass and of the Parent Plant, Yet is Necessary for Production of Viable Seeds

Freshly harvested seeds of soybean (Glycine max L. Merr.) orseeds shelled, then dried, were non-viable. Seeds dried in intactpods, even when only 17% of normal size, matured into viableseeds and produced healthy plants. These seeds maintained activityof various enzymes but gained little soluble protein while air-dryingin intact pods. There was a qualitative change in seed proteinsassociated with maturation. Seeds matured in intact pods havea greater proportion of protein as slow-moving bands and havecompletely lost one fast-moving band compared with seeds shelledbefore drying. Seed maturation is a distinct phase of seed production,is independent of the parent plant, and can be imposed on theseed at many stages of development.     

Basis of difference between reciprocal crosses involving Triticum boeoticum and T. urartu

Summary The boeoticum () X urartu () F₁ hybrids gave small, plump and viable seeds while the reciprocal crosses with T. urartu as the female parent had long, shrivelled and non-viable seeds. Reciprocal nuclear-substitution lines comprising the nucleus of one species into the cytoplasm of the other were developed through repeated backcrossing and were crossed as female parents with respective non-recurrent parents (the cytoplasm donors). The difference between the reciprocal crosses was presumably attributable to different boeoticum urartu genomic ratios in the triploid endosperm rather than to the cytoplasmic difference between the diploid wheats. The endosperm with two doses of the boeoticum and one of the urartu genome resulted in small, plump and viable seed while the endosperm of the reciprocal crosses with two doses of the urartu and one of the boeoticum genome led to large but shrivelled and non-viable seeds irrespective of the cytoplasmic type. One dose of the paternal genome in the triploid endosperm is probably not expressed in the presence of two doses of the maternal genome thereby leading to the difference between the reciprocal crosses. The results reported here indicate that difference between reciprocal crosses may not always be attributed to cytoplasmic difference between the parental species.     

Studies into Causes of Non-germination of Aged Wheat Seeds

Excised embryos of aged non-germinating wheat seeds, when placedon sucrose/glucose germinated well and grew into normal plantlets,while on agar alone they remained ungerminated as in the intactseed. From the results of amylase assays in seeds of differentages it appears that failure of amylolytic activity in agedseeds could be a cause of unavailability of utilizable subtrateto the embryonic axis of aged seeds. This would bring abouta limitation in the capacity of germination and growth of theembryonic axis even before the embryo becomes non-viable. Wheat (Triticum aestimon L. cv. Sonalilca), embryo, germination, sucrose, amylase     

Ascorbic acid metabolism in ageing recalcitrant sal (Shorea robusta Gaertn. f.) seeds

Changes in ascorbate content and its enzymatic utilization pattern were studied in embryonic axes and cotyledons of sal seeds undergoing rapid loss of viability, at ambient conditions. Ascorbate levels were significantly higher initially in the embryonic axes (0.32 mg/g fresh weight) and cotyledons (0.21 mg/g fresh weight) of freshly mature, relatively hydrated (42.2% moisture content) and 100% viable sal seeds. It declined sharply as the tissues; embryonic axes and cotyledons, desiccated with absolutely no detectable amount in non-viable seeds (21% moisture content). Significantly strong correlation was obtained between desiccation of embryonic axes (r = 0.96) and cotyledon (r = 0.97) with loss of ascorbate levels and loss of germinability. Higher rates of ascorbic acid utilization (AAU) recorded in the embryonic axes of 100% viable seed declined sharply as the seed viability reduced due to desiccation below 36.8% moisture content. AAU was not detected in the cotyledons.     

Changes in respiratory metabolism of rice seeds of varying viability

Respiratory metabolism in germs of rice seeds of varying germinative power was measured manometrically with the aid of inhibitors. Swelling of caryopses of high germinative power was accompanied by activation of the system glycolysis--Krebs cycle--respiratory chain and increase in the level of oxidation--phosphorylation coupling. Seed aging was associated with an enhancement of the phosphate respiratory pathway and a decrease in the rate of glycolysis during swelling and germination. Sensitivity to inhibitors of the mitochondrial electron transport chain was increased and oxidation--phosphorylation coupling decreased. In non-viable germs oxidation and phosphorylation were completely uncoupled.     

Consumption of flea faeces and eggs by larvae of the cat flea,Ctenocephalides felis

The effects of the consumption of flea faeces and non-viable eggs on larval development in the cat flea Ctenocephalides felis (Bouché) (Siphonaptera: Pulicidae) were investigated. Only 13.3% of larvae developed into adults when fed a diet of male or female flea faeces alone; however, 90% of larvae developed into adults when fed on flea faeces supplemented with non-viable flea eggs. When fed with non-viable eggs alone, larvae did not develop into adults. Nevertheless, non-viable eggs may provide critical supplemental nutrients, lacking in flea faeces and required for larval development. None of the larvae fed on flea faeces or non-viable eggs alone formed a cocoon. A diet of flea faeces alone significantly extended the second as well as third larval stadia compared to larvae fed on diets containing non-viable eggs. It is suggested that the cannibalism of fertile eggs may limit population growth in the cat flea.     

Change in respiration rate of rice seedlings as affected by storage and viability,and its possible relation with catalase and peroxidase activities during germination

Changes in the percentage of seed germination, the growth and respiration rate of the seedlings were observed at 15-day intervals from the stage of the full germination capacity of rice (Oryza saliva L.) seeds till they became non-viable. At the beginning, the respiration rate changed but little, but afterwards, with the approach of non-viability, the rate declined sharply. A positive correlation of respiration with a decrease in the germination percentage and the length of seedlings and a negative correlation with days of storage were also established. A strong correlation existed between catalase and peroxidase activity with respiration, indicating that the activity of these enzymes can be used as an indicator of metabolism, and therefore can be considered as part of the respiratory mechanism of rice seedlings.     

Proteolytic Activities in x Haynaldoticum sardoum Seeds of Different Ages

Carboxypeptidase, aminopeptidase and proteinase activities weremeasured in endosperms from dry and germinating x Haynaldoticumsardoum naturally aged seeds. Carboxypeptidase activity, presentin dry seeds, decreased slightly during germination and remainednearly unchanged during the storage period. Aminopeptidase activityincreased during germination in younger seeds, but decreasedin non-viable seeds. Proteinase activity was absent in dry seeds,increased during germination in younger seeds and disappearedin the older ones. Proteinase activity was not recovered in old endosperms followingtransplantation of young embryos, and was recovered only toa very small extent in young endosperms following transplantationof old embryos. Young endosperms onto which young embryos hadbeen transplanted gave maximum recovery of enzyme activity,although this was lower than in young intact seeds. These results suggest that the reduced or delayed availabilityof nutrients to the embryo axis is not the only factor causingthe failure of seeds to germinate, the ageing process beinga progressive phenomenon affecting both embryo and endosperm. x Haynaldoticum sardoum, Denti de cani, seed ageing, proteolytic activities, embryo-transplantation     

The structure of the seed in some Western Australian species of the genus Hibbertia (Dilleniaceae)

The internal structure of the seed was studied for four Western Australian species of the genus Hibbertia (Fam.: Dilleniaceae). The principal mechanical layer of the seed coat is the endotesta. The large cells of the endotesta are heavily cutinized in potentially viable seeds of all examined species. However, results for H. hypericoides show that the cells of the endotesta are distinctly less cutinized in non-viable seeds. The tegmen consists of only one layer which is spirally thickened. Remains of the nucellus enclose the endosperm. The endosperm is rich in both starch and lipids, and the embryo is underdeveloped and minute.     

Enumeration of viable Enterococcus faecalis, a predominant apical periodontitis pathogen, using propidium monoazide and quantitative real-time polymerase chain reaction

To discriminate between viable and non-viable Enterococcus faecalis, the predominant pathogen in apical periodontitis, a real-time PCR method combined with propidium monoazide (PMA) was developed and evaluated. PMA had no antimicrobial effect on E. faecalis cells and permitted enumeration of both viable and non-viable cells. Therefore, E. faecalis cells from the root canals of nine patients with apical periodontitis were analyzed to evaluate the diagnostic usefulness of this approach. Viable and non-viable E. faecalis cells were successfully discriminated in these clinical specimens. A real-time PCR assay combined with PMA will contribute to the precise diagnosis of apical periodontitis.     

Effects of seed manganese concentration on lupin emergence

Seed of narrow-leafed lupin (Lupinus angustifolius L.) produced in Western Australia often has low manganese (Mn) concentration because of low Mn availability in the soil during grain filling. A major problem of lupin production is poor seedling establishment. We tested the hypothesis that low Mn concentration in lupin seeds decreases emergence.The experiment was a factorial design comparing emergence of lupins (cv. Gungurru) grown under glasshouse conditions from seed with 2 different internal Mn concentrations (7 or 35 mg Mn kg^–1 DW) and with 2 external Mn fertiliser treatments (0 or 10 mg MnSO₄.H₂O kg^–1 soil). There were no visible differences between the seeds. Emergence was monitored and plants were harvested 17 days after sowing.Emergence was approximately 60% in all pots sown with low Mn compared to 100% in pots sown with high Mn seed. Application of Mn did not increase the final emergence of low Mn seed. Seed viability was assessed by staining with tetrazolium chloride, a common test used in seed testing laboratories. All high Mn seed were viable while 34% of low Mn seed were completely or partly unstained and therefore were non-viable. We have shown that low Mn supply during seed filling may lead to production of non-viable seed that cannot be visually distinguished from viable seed..     

Gene mutations in rye causing embryo lethality in hybrids with wheat: allelism and chromosomal localisation

In crosses between hexaploid wheat and inbred lines of rye, a small number of rye genotypes produce seeds carrying undifferentiated, non-viable embryos. Hybrids between such lines and those not showing this phenotype were used as pollen donors in crosses with bread wheat in order to determine the genetic basis of disturbed embryo development. A single gene, designated Eml-R1b, is causing this character. Molecular markers associated with F₂ genotypes derived from a contrasting rye inbred progeny were used for a linkage study. Recombinant inbred lines of an F₅ population served as testers. Eml-R1b maps to chromosome arm 6RL, along with two co-segregating microsatellite loci, Xgwm1103 and Xgwm732. Complementary interactions of deleterious genes in wheat and rye are discussed.