Germination responses of Erica andevalensis to different chemical and physical treatments

Breaking Dormancy and Enhancing Germination of Avena sterilis L. and Amaranthus retroflexus L. Weeds by Gibberellic Acid and Potassium Nitrate to Keep Soil and Crops Healthy

Soils infested with weed seeds are considered hostile lands for crop production. In this context, great wild oat (Avena sp.) in winter seasons and redroot pigweed (Amaranthus sp.) in summer seasons represent problematic weeds in cropland fields. In a series of laboratory trials, we estimated the effects of gibberellic acid (GA3) and potassium nitrate (KNO3) on germination and seedling growth of Avena sterilis L. and Amaranthus retroflexus L. Different concentrations of GA3 and KNO3 were evaluated in randomized complete block design with four replicates. Findings revealed that GA3 at a rate of 200 mg L−1 along each of 150 and 250 mg L−1 treatment showed the maximum increases in germination percentage, radicle length, plumule length and seedling dry weight of A. sterilis L. All applied concentrations of KNO3 were similar (p ≥ 0.05) in enhancing seed germination of A. sterilis L. exceeding the control treatment. Application of GA3 at rates of 250, 500 and 750 mg L−1 surpassed the treatments of 0 and 1000 mg L−1 GA3 for activating A. retroflexus L. seeds germination. Addition of 250 and 500 mg L−1 KNO3 were the potent treatments for stimulating the radicle length of A. retroflexus L. It could be concluded that for breaking dormancy efficiently, addition of gibberellic acid or potassium nitrate with Avena sterilis L. as well as gibberellic acid with Amaranthus retroflexus L. is recommended. Such chemicals could be involved in weed management programs, since distinctive promotion of seed germination for the target weeds was achieved. This undoubtedly will keep the soil and crops healthy.

Physiological response of Cistus salviifolius L. to high arsenic concentrations

Arsenic is a trace element found in the environment which can be particularly toxic to living organisms. However, some plant species such as those of the genus Cistus are able to grow in soils with high As concentrations and could be used in the sustainable rehabilitation of mining areas through phytostabilization. In this work, the growth and the physiological response of Cistus salviifolius L. to As-induced oxidative stress at several concentrations (reaching 30 mg L^-1) in an hydroponic system were evaluated for 30 days. Several growth parameters, chlorophyll content, chemical composition, one indicator of oxidative stress (H₂O₂) and two of the major antioxidative metabolites (ascorbate and glutathione) were analysed. The toxic effect of As was better perceived in the plants submitted to treatments with concentrations of 20 and 30 mg As L^-1. Plants subjected to these treatments had higher concentration of As in roots and shoots. The concentrations of Ca, Mg, K and Fe in the plants as well as a large part of the evaluated growth parameters were also affected. Arsenic did not interfere with the ability of the plant to perform photosynthesis, as there were no significant differences in the contents of chlorophyll a, b and total between the different treatments. Plants from all treatments accumulated higher amount of As in roots than in shoots, and it was also in the roots that the concentrations of H₂O₂, AsA and GSH were higher. Cistus salviifolius showed high tolerance to As up to the concentration of 5 mg L^-1, which makes it a species with high potential to be used in the phytostabilization of soils contaminated with As and presenting high concentrations of the element in the soil solution.

Swailing affects seed germination of plants of European bio-and agricenosis in a different way

Swailing as a part of agricultural practice is an illegal habit in many European countries. The indirect effect of swailing is the emission of volatiles (SGV), hence the aim of the study was to identify their impact to seeds of different species occurring or grown Europe. It was carried out on seeds of 29 species of 10 botanical families within the angiosperms. The response to SGV was more or less differentiated within a family, and even within the species, e.g. in the case of tomato. The stimulation of germination and/or increased seedling vigour was established in celery, green- and red-leafed basil, white and red cabbage, white clover and wild thyme. The same effect was noticed for the seeds of stratified broadleaf plantain and the positively photoblastic seeds of German chamomile germinated in darkness. The inhibition of seed germination and/ or reduced seedling vigour was demonstrated in case of caraway, dill and forget-me-not. Similar results were obtained in the experiments carried outin vitroand in the soil, hence it can be assumed that the indirect impact of SGV on plant habitat composition is likely. The interaction of SGV compounds with seed testa and seed phytohormones is discussed.

Antibiotics impact plant traits, even at small concentrations

Antibiotics of veterinary origin are released to agricultural fields via grazing animals or manure. Possible effects on human health through the consumption of antibiotic exposed crop plants have been intensively investigated. However, information is still lacking on the effects of antibiotics on plants themselves, particularly on non-crop species, although evidence suggests adverse effects of antibiotics on growth and performance of plants. This study evaluated the effects of three major antibiotics, penicillin, sulfadiazine and tetracycline, on the germination rates and post-germinative traits of four plant species during ontogenesis and at the time of full development. Antibiotic concentrations were chosen as to reflect in vivo situations, i.e. concentrations similar to those detected in soils. Plant species included two herb species and two grass species, and represent two crop-species and two non-crop species commonly found in field margins, respectively. Germination tests were performed in climate chambers and effects on the remaining plant traits were determined in greenhouse experiments. Results show that antibiotics, even in small concentrations, significantly affect plant traits. These effects include delayed germination and post-germinative development. Effects were species and functional group dependent, with herbs being more sensitive to antibiotics then grasses. Responses were either negative or positive, depending on plant species and antibiotic. Effects were generally stronger for penicillin and sulfadiazine than for tetracycline. Our study shows that cropland species respond to the use of different antibiotics in livestock industry, for example, with delayed germination and lower biomass allocation, indicating possible effects on yield in farmland fertilized with manure containing antibiotics. Also, antibiotics can alter the composition of plant species in natural field margins, due to different species-specific responses, with unknown consequences for higher trophic levels.

Germination and Clonal Propagation of the Endemic Shrub Corema album, a Vulnerable Species with Conservation Needs and Commercial Interest

In this study, we aimed to explore regeneration possibilities of Corema album (L.) D. Don by determining germination mechanisms and testing vegetative propagation methods. We analyzed seed viability under natural conditions, carried out germination treatments and a greenhouse experiment to study clonal propagation. We confirmed that C. album seeds present physiological dormancy, broken by ingestion by natural dispersers (rabbits and foxes), and that seed viability under natural conditions is lost after one year. In vitro germination was better achieved with a 200 ppm gibberellic acid treatment. Clonal propagation proved to be a successful technique for the production of C. album. Treating cuttings with IBA 0.2, w/v, at 20% resulted in the highest rooting percentage, while planting rooted cuttings in a substrate of perlite with vermiculite 1:1 was essential for plant survival. Our results show that both germination pretreatments and cutting propagation are powerful tools for the production of this valuable species. Both methods could be incorporated for population regeneration in natural habitats, and for the potential establishment of the species as a new crop for consumption and pharmacological purposes.

Response of drought and fertilization in Erica andevalensis seed banks: significance for conservation management

The present study attempts to investigate the size, composition and seedling dynamics of the seed bank of a metalliferous and vulnerable species, Erica andevalensis. Samples were taken during spring and autumn from two different sites. We also studied the effects of nutrient solution, irrigation from the river Tinto and irrigation deficit on seeding establishment and survival. Only E. andevalensis and Poaceae species emerged from the seed banks, although the former was dominant (98%). Germination and seedling establishment was totally inhibited by the waters of the river Tinto. Seed density was high in the soils of both seed banks irrigated with water and nutrient solution. We found no seasonal differences in the seed bank and number of germinated seeds and mortality rate and density were similar. From the standpoint of restoration management, the results indicate that the seed bank is a very important factor for successful species establishment.

Selective uptake of major and trace elements in Erica andevalensis, an endemic species to extreme habitats in the Iberian Pyrite Belt

To assess the ecophysiological traits and the phytoremediation potential of the endemic heather Erica andevalensis, we determined the concentrations of major and trace elements in different plant parts and in rizosphere soils from Riotinto mining district (Huelva, Spain). The results showed that E. andevalensis may grow on substrates with very high As, Cu, Fe and Pb concentrations (up to 4114, 1050, 71900 and 15614 microg/g dry weight, respectively), very low availability of macro- and micronutrients and with pH values ranging from 3.3 to 4.9. In these harsh edaphic conditions E. andevalensis selectively absorbed and translocated essential nutrients and excludes potentially phytotoxic elements, which were accumulated in the root epidermis. The concentrations of major and trace elements in E. andevalensis aerial parts from the Riotinto mining district were in the normal range for plants; likewise other Erica species it accumulated Mn and only in a very polluted site we measured leaf concentrations of As and Pb within the excessive or toxic limits for plants. Differently from previous studies, which emphasized the soil pH and bioavailability of phytotoxic elements as the main stress factors, this study showed that in the Riotinto region, E. andevalensis can tolerate wide range of pH and toxic element concentrations; the harshest environments colonized by monospecific patches of this species were characterized above all by very low availability of nutrients. The extraordinary capability to adapt to these extreme habitats made E. andevalensis a priority species to promote the phytostabilization and the development of a self-sustaining vegetative cover on Riotinto mine tailings.

Germination and establishment of the invasive cordgrass Spartina densiflora in acidic and metal polluted sediments of the Tinto River

Heavy metal pollution is common in rivers in the vicinity of mining areas. In these polluted environments, the survival of alien species with a high tolerance to metals may be favored. The Tinto River (Southwest Iberian Peninsula) is an excellent natural laboratory for the study of plants' responses to acidic and metal polluted sediments. This work analyzes the tolerance of the alien species Spartina densiflora to low pH and high metal loads in the Tinto River. The main aim of this study was to determine if this alien species can invade landward along the banks of the Tinto River. S. densiflora seeds were able to germinate in heavy metal polluted aerobic sediments even at pH 2. However, these conditions decreased S. densiflora final germination, altered germination dynamics, decreased aerial and subterranean growth rates, and prevented its establishment.