Paper presented a mathematical model of seed germination process based on the Monte Carlo method and theoretical premises resulted from the physiology of seed germination suggesting three consecutive stages: physical, biochemical and physiological. The model was experimentally verified by determination of germination characteristics for seeds of ground tomatoes, Promyk cultivar, within broad range of temperatures (from 15 to 30 deg C)

In our country the maindenhair tree (Ginkgo biloba L.) is raised mainly from seeds, so the aim of our experiments was to determine the most useful generative propagation method. However, some experiments have been conducted earlier connected to the germination of the species, but the comparative control of physical seed treatment was done first time by the authors. After the statistical evaluation of the results it can be stated that the percentage of germination has significantly increased if the seeds received physical treatment (scalding, mechanical scouring). Hereby the pericarp is getting soft or growing thinner, so the germination of the seed is easier. These treatments are extraordinarily simple, easy to carry out and their effect is very favourable, that is why their use is strongly advised. Comparing the seeds collected at different times was found that the ability of germination is decreasing proportionally with the time spent in the open field. On the basis of our experiments and of earlier practice in Hungarian tree nurseries, our opinion is that the stratification of seeds is not necessary.

In this work, we have used spores of Bacillus subtilis that specifically induce bioluminescence upon initiation of germination as a rapid, real-time monitor of the effects of preservative treatments on germination. Using this tool, we have demonstrated that the combination of mild acidity (pH 5.5 to 5.0), lactic acid (0.5%), and a pasteurization step (90 degrees C for 5 min) results in enhanced inhibition of spore germination compared with the effects of the individual treatments alone. Inhibition by the combination treatment occurred as a result of both direct but reversible inhibition, entirely dependent on the physical presence of the preservative factors, and permanent, nonreversible damage to the L-alanine germination apparatus of the spore. However, we were able to restore germination of the preservative-damaged spores unable to germinate on L-alanine by supplementing the medium with the nonnutrient germinant calcium dipicolinic acid. The demonstration that simple combinations of preservative factors inhibit spore germination indicates that food preservation systems providing ambient stability could be designed which do not adhere to the strict limits set by commonly accepted processes and which are based on precise understanding of their inhibitory action.

Ecotoxicological assessments of contaminated soils require an understanding of the impact of chemicals on the terrestrial ecosystem. Eight hydrocarbon-containing field soils were evaluated using physical-chemical, hydrocarbon, and ecotoxicological assays during 11 to 13 months of laboratory bioremediation. Ecotoxicity tests included earthworm (Eisenia fetida) 14-d survival and reproduction assays and seed germination and root length assays using corn, lettuce, mustard, and wheat seeds. During bioremediation, freon-extractable total petroleum hydrocarbon decreased by 26 to 84%, depending on the soil. In most soils, earthworm survival increased to or remained at 100% following bioremediation. Earthworm reproduction increased or remained the same relative to control soils. Lettuce and mustard seed germination increased following bioremediation except in two soils with high salt concentrations. Corn and wheat germination was high on most soils and did not change following bioremediation. Root length responses varied among seeds and soils, increasing in some soils and remaining unchanged in others. The responses of organisms to hydrocarbon-containing field soils directionally improved with bioremediation.

The testa of higher plant seeds protects the embryo against adverse environmental conditions. Its role is assumed mainly by controlling germination through dormancy imposition and by limiting the detrimental activity of physical and biological agents during seed storage. To analyze the function of the testa in the model plant Arabidopsis, we compared mutants affected in testa pigmentation and/or structure for dormancy, germination, and storability. The seeds of most mutants exhibited reduced dormancy. Moreover, unlike wild-type testas, mutant testas were permeable to tetrazolium salts. These altered dormancy and tetrazolium uptake properties were related to defects in the pigmentation of the endothelium and its neighboring crushed parenchymatic layers, as determined by vanillin staining and microscopic observations. Structural aberrations such as missing layers or a modified epidermal layer in specific mutants also affected dormancy levels and permeability to tetrazolium. Both structural and pigmentation mutants deteriorated faster than the wild types during natural aging at room temperature, with structural mutants being the most strongly affected.

Three physical treatments viz. sand paper scraping, beating and hot water treatments and two chemical treatments viz. concentrated sulphuric acid and ethyl alcohol were included in the study. These treatments were applied on seeds of two sizes viz. large and small. Results of the experiments revealed that sand paper scraping and concentrated H2SO4 showed more effective performance than beating and hot water treatments in breaking seed dormancy of Sesbania rostrata. Ethyl alcohol had no effect on breaking seed dormancy. Large seed showed lesser dormancy than small one. Sand paper scraping (13 revolutions) of large seed gave the highest germination (97.8%).

Seed germination is influenced by several physical and chemical factors, both internal and external. Rocket (Eruca sativa Mill.) has very small seeds, characterized by low germination capacity and vigour. A trial was carried out in germination cabinet, using osmo-priming technique, to study 4 levels of osmotic pressure, determined by 0, 10, 20 and 30 g l*[-1) of potassium nitrate (KNO3) or 0, 145, 172 and 194 g l*[-1) of polyethylene-glycol (PEG); 4 soaking times and 5 preservation periods. The effects of KNO3 and PEG were considerably different, with regard to both concentration and soaking time. On the whole, PEG gave the best results when soaking was performed at 444 mOs pressure level, for 8 days | [La germinazione dei semi e' influenzata da numerosi fattori fisici e chimici, sia interni, sia esterni. La rucola (Eruca sativa Mill.) produce semi molto piccoli, caratterizzati da bassa germinabilita' e basso vigore. E' stata condotta una prova in germinatoio, utilizzando la tecnica dell'osmo-priming, per studiare 4 livelli di pressione osmotica, determinati da 0, 10, 20 e 30 g l*[-1) di nitrato di potassio (KNO3) o 0, 145, 172 e 194 g l*[-1) di polietilenglicole (PEG), con 4 tempi di agitazione e 5 periodi di conservazione. Gli effetti del KNO3 e del PEG erano molto diversi, rispetto sia alla conservazione, sia al tempo di agitazione. In complesso, il PEG ha dato i miglior risultati quando l'agitazione era effettuata al livello di pressione di 444 mOs, per 8 giorni]

10 páginas, 3 figuras, 3 tablas, 1 apéndice. | The possible causes for the lack of vegetation in five badland sites from southeast Spain were experimentally tested. The main factors affecting seed germination and seedling survival considered were seed availability, regolith water dynamics in relation to rain events, regolith salinity, seedling predation by herbivores and seedling removal by erosion. Four issues are addressed: 1. Both rainfall and the temporal and spatial dynamics of regolith water during the seedling emergence period were monitored in five different zones at one site (Petrer, Alicante). 2. Effects of salinity and water potential on the rate and speed of germination of local seeds were determined. 3. Seed reserve and seedling emergence and mortality were followed throughout one season. 4. Regolith characteristics of all five sites were compared and the consequences for plant colonization discussed. The main factor limiting plant colonization in these sites was the very short duration of available water in the soil, due to the physical and chemical characteristics of the regolith. In addition, high regolith salinity and its effects on seed germination, the aspect of the site and the pattern of rain events, played a very important role reducing germination and survival. Herbivory and erosion were seldom responsible for seedling mortality. However, there were no highly erosive rain events during the study period, although several have been measured during the past few years. | We thank José Martínez and Amparo Soriano for providing data on soil properties and Adolfo Calvo and Alejandro Pérez-Cueva for providing meteorological data. Adolfo Calvo, Vicente Monleón and Vicente Pons helped with field and laboratory work. We are very grateful to Vicente Monleón, Carolina Hooper, Francisco Lloret, Adolfo Calvo, Miguel Verdú and two anonymous reviewers for their constructive comments on the manuscript. Mario Payá and his family granted permission to access and work on their property and assisted in the fieldwork. This study was supported by the Spanish Comisión Interministerial de Ciencia y Tecnología (projects NAT89-1072-C06-04 and AMB93-0844-C06-04). | Peer reviewed