Effects of urea on the germination and early growth of kale,barley, and wheat

Summary Kale was grown in pots in the glasshouse and barley and wheat in bottomless boxes in the open with increasing amounts of urea applied to the soils maintained at various moisture contents. Two sandy soils and two clay soils (one of each containing much and little organic matter) were used in both pots and boxes; in addition four calcareous soils (two developed over chalk, and two over hard limestone) were used in the boxes to compare the effects of the applied urea on the germination and early growth of crops on different soils.The greatest amount of urea applied to the soils containing little organic matter decreased growth of kale in pots, particularly on drier soils, but did not affect growth on soils containing much organic matter; in contrast, with barley and wheat grown in boxes, urea was more damaging in the soils containing much than in those with little organic matter.The various soils used could be grouped according to the amount of urea giving maximum yield. On a soil containing much free calcium carbonate derived from chalk, urea either did not affect yield or depressed it below that of the unfertilised crop.     

Metabolism of barley seed during early hours of germination

The growth process in germinating barley seeds and its inhibition by actinomycin D and puromycin were investigated. Soon after seeds are imbided, their respiratory activity increases several fold, and the protein- and carbohydrate-synthesizing systems become active. The immediate activation of protein synthesis and its inhibition by actinomycin D and puromycin suggest that the dry seed has all the components necessary for protein synthesis.     

Ethylene is differentially regulated during sugar beet germination and affects early root growth in a dose-dependent manner

Main conclusion

By integrating molecular, biochemical, and physiological data, ethylene biosynthesis in sugar beet was shown to be differentially regulated, affecting root elongation in a concentration-dependent manner. There is a close relation between ethylene production and seedling growth of sugar beet (Beta vulgaris L.), yet the exact function of ethylene during this early developmental stage is still unclear. While ethylene is mostly considered to be a root growth inhibitor, we found that external 1-aminocyclopropane-1-carboxylic acid (ACC) regulates root growth in sugar beet in a concentration-dependent manner: low concentrations stimulate root growth while high concentrations inhibit root growth. These results reveal that ethylene action during root elongation is strongly concentration dependent. Furthermore our detailed study of ethylene biosynthesis kinetics revealed a very strict gene regulation pattern of ACC synthase (ACS) and ACC oxidase (ACO), in which ACS is the rate liming step during sugar beet seedling development.     

Synthesis of the peptide-transport carrier of barley scutellum during the early stages of germination

Development of peptide-transport activity in the scutella of isolated barley (Hordeum vulgare l. cv. Maris Otter, Winter) embryos is shown to increase rapidly after about 15 h of imbibition, with the bulk of the transport activity being expressed by 24 h. This development is prevented by treatment of 15 h embryos with cycloheximide. Protein synthesis is found to increase in a closely related manner and also to be abolished by cycloheximide. Measurement of the incorporation of bound [³⁵S]methionine by 15 to 21-h embryos indicates that de-novo protein synthesis during this period is greater in the scutellum than in the embryonic axis. Previous studies have shown that the peptide-transport system possesses essential dithiol groups, probably located at the substrate-binding site (Walker-Smith and Payne 1983 b, 1984b). Treatment of 15-h embryos with the non-penetrant thiol reagent p-chloromercuribenzene sulphonic acid did not affect development of peptide-transport activity during the following 6 h, whereas with 3-d embryos identical treatment inhibited uptake almost completely during a subsequent 6-h period. Radioautography revealed that amongst the proteins synthesised during this early phase of germination and labelled in vitro with [³⁵S]methionine some are found within the epithelial plasmalemmae of the scutellum, which is the location of the peptide-transport carrier identified previously by externally labelling with a radioactive thiol reagent. The results provide evidence that protein(s) of the peptide-transport system are synthesised and inserted into the scutellum during early germination, allowing the system to play a major role in the nitrogen nutrition of the embryo.Abbreviations Gly Glycine - Phe phenylalanine     

Biochars influence seed germination and early growth of seedlings

Plant and Soil - Biochar can be produced from a wide range of organic sources with varying nutrient and metal concentrations. Before making irreversible applications of biochar to soil, a...     

Ethylene in seed dormancy and germination

The role of ethylene in the release of primary and secondary dormancy and the germination of non-dormant seeds under normal and stressed conditions is considered. In many species, exogenous ethylene, or ethephon – an ethylene-releasing compound - stimulates seed germination that may be inhibited because of embryo or coat dormancy, adverse environmental conditions or inhibitors (e.g. abscisic acid, jasmonate). Ethylene can either act alone, or synergistically or additively with other factors. The immediate precursor of ethylene biosynthesis, 1-aminocyclopropane-1-carboxylic acid (ACC), may also improve seed germination, but usually less effectively. Dormant or non-dormant inhibited seeds have a lower ethylene production ability, and ACC and ACC oxidase activity than non-dormant, uninhibited seeds. Aminoethoxyvinyl-glycine (AVG) partially or markedly inhibits ethylene biosynthesis in dormant or non-dormant seeds, but does not affect seed germination. Ethylene binding is required in seeds of many species for dormancy release or germination under optimal or adverse conditions. There are examples where induction of seed germination by some stimulators requires ethylene action. However, the mechanism of ethylene action is almost unknown.
The evidence presented here shows that ethylene performs a relatively vital role in dormancy release and seed germination of most plant species studied.     

Ethylene, seed germination, and epinasty

Ethylene activity in lettuce seed (Lactuca satina) germination and tomato (Lycopersicon esculentum) petiole epinasty has been characterized by using heat to inhibit ethylene synthesis. This procedure enabled a separation of the production of ethylene from the effect of ethylene. Ethylene was required in tomato petioles to produce the epinastic response and auxin was found to be active in producing epinasty through a stimulation of ethylene synthesis with the resulting ethylene being responsible for the epinasty. In the same manner, it was shown that gibberellic acid stimulated ethylene synthesis in lettuce seeds. The ethylene produced then in turn stimulated the seeds to germinate. It was hypothesized that ethylene was the intermediate which caused epinasty or seed germination. Auxin and gibberellin primarily induced their response by stimulating ethylene production.     

Identification and expression analysis of miRNAs in germination and seedling growth of Tibetan hulless barley

Germination and seedling growth are crucial for plant development and agricultural production. While, the regulatory mechanisms during these processes in Tibetan hulless barley (Hordeum vulgare L. var. nudum) are not well understood. Given the regulatory roles of microRNAs (miRNAs) in crop plants and the irreplaceability of barley in the highland area of China, we herein presented a genome-wide survey of miRNAs to reveal a potential regulatory network in the early developmental stages of two Tibetan hulless barleys, from which a total of 156 miRNAs was identified including 35 known and 121 novel ones. Six of the identified novel miRNAs were further experimentally validated. According to the evolutionary analysis, miR156, miR166, miR168, and miR171 were conserved across Tibetan hulless barleys and eight other seed plants. Expression profiles of ten known miRNAs showed that they were involved in phytohormone signaling, carbohydrate and lipid metabolism, as well as juvenile-adult transition during barley development. Moreover, a total of 1280 genes targeted by 101 miRNAs were predicted from both barley libraries. Three genes (PLN03212, MATE eukaryotic, and GRAS) were validated via the RNA ligase-mediated 5′-rapid amplification of cDNA ends (RLM-5' RACE) to be the targets of hvu-miR159a, hvu-miR166a, and hvu-miR171-3p, respectively. Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis of putative targets, the most abundant pathways were related to “metabolism”.These results revealed that miRNA-target pairs participating in the regulation of multigene expression and the embryonic development of Tibetan hulless barleys were controlled by complex mechanisms involving the concordant expression of different miRNAs and feedback loops among miRNAs as well as their targets. The study provides insight into the regulatory network of barley miRNAs for better understanding of miRNA functions during germination and seedling growth.     

DNA synthesis during the early stage of germination in the barley embryo meristems and its inhibition by N-methyl-N-nitrosourea

3 peaks of DNA synthesis were observed in the barley embryo of seeds, germinating for 49 h in running tap water at 25°C. The first peak, found after 22h, was formed by S-cells in the roots and in the 1st leaf meristem. The second peak (after 34–37h) and third peak (after 46–49 h) represents the S-cells in the roots, apex and 1st, 2nd and 3rd leaf meristems. Application of N-methyl-N-nitrosourea for 3 h at the onset of germination inhibited the rate of DNA synthesis and postponed the peaks of DNA synthesis in individual meristems of the embryo.     

Ethylene biosynthesis and strigol-induced germination of Striga asiatica

Germination of witchweed [ Striga asiatica (L.) Kuntze], an important parasite on cereal crops, is stimulated by several natural and synthetic compounds. In the present study the role of ethylene in germination of Striga asiatica in response to strigol was examined. Unconditioned seeds and those conditioned for 3 days produced negligible amounts of ethylene in response to strigol. However, extending the conditioning period to 5 and 8 days increased ethylene evolution by more than 10-fold. Ethylene production preceded radicle protrusion and was detectable within 3h after treatment. No germination was observed in the first 6 h of exposure to strigol. Germination and ethylene production increased with strigol concentration. Strigol-induced germination was considerably reduced by the ethylene action inhibitors. 2. 5-norbornadiene, silver thiosulphate and CO₂. The ethylene precursor 1-aminocyclopropane-1-carboxyac acid (ACC) at 5 to 200 μ M elicited neither germination nor ethylene production. However, a combination of strigol and ACC resulted in a high germination rate and copious ethylene production. Both germination and ethylene production were reduced by CoCl₂ and cyclobeximide, inhibitors of the ethylene-forming enzyme and of protein synthesis, respectively. The results are consistent with a model in which conditioning and strigol are required to remove a restriction on the ethylene biosynthetic pathway and in which the ethylene-forming enzyme is rate limiting.     

Effect of plant growth hormones and polyamines on ornithine decarboxylase activity during the germination of barley seeds

Gibberellic acid (GA₃) and β-indolylacetic acid (IAA), two of the well known growth hormones, induce four fold the activity of ornithine decarboxylase (ODC) during the germination of barley seeds ( Hordeum vulgare L. var. Beca). The optimal concentration for induction of ODC was 10^–5 M for GA₃ and 10^–3 M for IAA. When 10^–3 M of a polyamine, putrescine or spermidine, is added to the growth medium, ODC activity is significantly inhibited. This inhibition is due to the induction of a protein inhibitor of ODC (antizyme), whose apparent molecular weight is 16 000 ± 2 000 daltons. Addition of GA₃ to cultures which have been grown for 50 or 98 h in the presence of polyamines, abolishes the observed inhibition of ODC activity, while in the reverse experiment, addition of polyamines at 50 or 98 h does not affect the ODC activity induced by GA₃. Cadaverine, a physiological plant diamine, enhances ODC activity; whereas 1,8-diaminooctane (the alkyl analogue of spermidine) does not have any effect.     

Gene expression in the soybean seed axis during germination and early seedling growth

Copy-DNA clones have been obtained that distinguish eight messenger mRNAs, moderately abundant in the axes of the germinating soybean (Glycine max (L.) Merr.) seedling. These clones have been used to characterize the size of the mRNAs and to anlyze the accumulation of the mRNAs at different time points and in different parts of the axis during germination and early seedling growth. Three of the mRNAs accumulate to a substantial level by 9 h, a time point before either the beginning of growth or the accumulation of polyribosomes. Four other mRNAs reach a substantial level only at 24 h, a period when rapid seedling growth is occurring. Those mRNAs whose accumulation begins at 24 h were found only in the top (hypocotyl) half of the 24-h seedlings, while the remaining mRNAs were present also in the bottom half of the seedlings in different amounts. By 44 h, the bottom 0.5 cm of the seedlings, i.e., the region of meristematic growth, had little or none of the mRNAs, with the exception of one mRNA. These temporal and spatial observations indicate that many of the mRNAs are not involved simply in the general maintenance of ongoing cell proliferation, but that they may be related to differentiation during early seedling formation. Further, the early accumulating mRNAs may be functioning in regulating the onset of seedling growth.Abbreviations cDNA copy DNA - poly(A)⁺RNA polyadenylated RNA     

Thioredoxin h overexpressed in barley seeds enhances selenite resistance and uptake during germination and early seedling development

The uptake, distribution and metabolism of selenite were examined in germinating homozygous barley (Hordeum vulgare L.) grain with thioredoxin h overexpressed in starchy endosperm. Results were related to the null segregant in which the transgene had segregated out during crossing. Compared with the null segregant, the homozygote showed enhanced germination and root and shoot growth in the presence of 1 and 2 mM sodium selenite. The rate of incorporation of selenite by the homozygote was approximately twice that of the null segregant. Based on X-ray absorption spectroscopy, the major products in both cases were selenomethionine-like species and the red, monoclinic form of elemental selenium, a derivative not previously reported in green plants. Selenite and selenate made up the balance. The distribution of the products formed differed as to the tissue — root, shoot, aleurone, endosperm — but the ratios were similar in the homozygote and null segregant. The results provide evidence that, in addition to the accelerated germination observed previously in water, barley grain overexpressing thioredoxin h are resistant to the inhibitory effects of selenite. These properties raise the possibility that plants overexpressing thioredoxin h could find application in the remediation of polluted environments.     

Mitochondrial folates and methionyl-tRNA transformylase activity during germination and early growth of seeds

Mitochondria were isolated from the cotyledons of pea (Pisum sativum cv Homesteader) and peanut (Arachis hypogaea cv Early Spanish) seeds over a 7-day growth period. The rate of mitochondrial oxygen uptake increased 3-4-fold during the first 4 days of growth and parallel changes were observed in the respiratory control and ADP/O ratios. In both species, the total cotyledonary pool of folate derivatives increased 3-4-fold during this period of germination whereas that associated with isolated mitochondria increased 5-10-fold. Until day 3 of growth, the mitochondrial folates were principally polyglutamates of 10-formyltetrahydrofolate but between day 4 and day 7 increasing levels of 5-methyltetrahydrofolate polyglutamates were detected. Pea and peanut mitochondria contained methionyl-tRNA transformylase (EC 2.1.2.9) activity that displayed an absolute requirement for 10-formyl-tetrahydrofolate. The specific activity of this enzyme rose during germination, reaching maximal levels between days 3 and 4. Isolated pea mitochondria had the ability to incorporate [³H]leucine and [³⁵S]methionine into protein in a reaction that required ADP and malate but was strongly inhibited by chloramphenicol. Organelles isolated after 4 days of germination incorporated leucine at rates ca 5-fold greater than shown by mitochondria of 16-hour-old seedlings. The inter-relationships between respiratory activity, mitochondrial formyltetrahydrofolates and methionyl-tRNA transformylase activity suggest a role for organelle protein synthesis during germination of these legume species.     

Ethylene requirement during germination of Botrytis cinerea spores

Application of 2,5-norbornadiene, a competitive inhibitor of ethylene, effectively inhibited the germination of Botrytis cinerea Pers. ex Fr. spores. The transfer of spores from 2,5-norbornadiene to air relieved inhibition by norbornadiene, indicating that its effects are non-toxic and reversible. Ethephon (2-chloroethylophosphonic acid), which stimulates spore germination of B. cinerea , does not affect germination in the presence of norbornadiene. However, ethephon appeared to be effective in relieving inhibition, when norbornadiene was removed from the atmosphere surrounding spores. The addition of ethylene to an atmosphere enriched with norbornadiene, counteracted the inhibition of spore germination. The inhibition of spore germination by 2,5-norbornadiene and the reversal of this effect by ethephon or ethylene, indicate that the action of ethylene is indispensable for germination of B. cinerea spores.     

Mobilisation of storage reserves during germination and early seedling growth of sugar beet

The principal storage reserve of sugar beet seeds is starch, which is localised in the perisperm. Additional storage reserves include the seed proteins, albumins, globulins and glutclins, which are exclusively located in the embryo. Soluble sugars are also detectable in all the organs of the mature seed. The time-course of reserve mobilisation in the different organs of the sugar beet ( Beta vulgaris L. cv. Regina) seed during germination and early seedling growth is documented, with particular reference to changes in (a) activities of hydrolases: a-amylase, β-amylase, and α-glucosidases; (b) levels of carbohydrates and (c) proteins. Amylase activities increase substantially in both cotyledons, as well as the perisperm, whereas the increase in α-glucosidase activities is largely confined to the perisperm.     

The inhibitory effect of NaCl on barley germination

Abstract The possibility that the nature of the inhibitory effect of NaCl is different during imbibition compared to germination was investigated. Germination in both NaCl and betaine (a non-toxic solute) improved with pre-imbibition in water. Seeds imbibed in inhibitory concentrations of either solute could be induced to germinate by brief exposure to water. Electron micrographs of tissue from seeds imbibed in 0.5 kmol m^?3 NaCl for 25 h showed cells identical to those in seeds imbibed in water for only 1 h, but seeds imbibed for 6 h in water exhibited many changes in ultrastructure. These results are consistent with the hypothesis that seed hydration must reach a critical value before germination can proceed, and that the inhibitory effect of NaCl is primarily osmotic in barley seeds that have not reached this hydration threshold. Although isotonic solutions of betaine and NaCl were equally inhibitory to germination, isotonic solutions of betaine and NaCl were not equally inhibitory to continued development in seeds which had been pre-imbibed in water. Calcium ions improved both germination and plumule emergence of pre-imbibed seeds in NaCl solutions, but calcium had little effect on pre-imbibed seeds placed in betaine. Very high concentrations of NaCl or betaine inhibited germination, but did not kill dry seeds. Both solutes, on the other hand, were lethal at high concentrations to germinating seeds. NaCl killed germinating seeds more rapidly than betaine, but calcium reduced the rate of killing to nearly that of betaine. We conclude that hydrated seeds are sensitive to both osmotic and toxic effects of NaCl and that calcium mitigates the toxic effect of NaCl, but not the osmotic effect.     

Stability of citrinin and deoxynivalenol during germination process of barley

The stability of citrinin and deoxynivalenol during germination process of barley spiked with these mycotoxins at a level of 2/ig/g was investigated. Germinated barley was analyzed after 1, 3, and 5 days to follow the stability of citrinin and deoxynivalenol during the germination process. Two thin layer chromatographic methods were used for determinations of citrinin and deoxynivalenol. An average of 93.6% of citrinin and 77.1% of deoxynivalenol were destroyed within 5 days during the germination process of barley.