Evolutsioonilised seosed taimede konkureerimiskäitumise ning naabrite identiteedi ja esinemissageduse vahel parasvöötme niidukooslustes

Väitekirja elektrooniline versioon ei sisalda publikatsiooneTaimed on paikse eluviisiga ning võivad reageerida välistingimustele morfoloogilise plastilisuse abil. Plastilised reaktsioonid ilmnevad mitte ainult eluta loodusele, vaid ka naabertaimede identiteedile (liigikaaslastele või teiste liikide esindajatele, sugulastele või mittesugulastele). Koosluses toimuvad evolutsioonilised protsessid võivad vormida taimeliigi plastilisust juhul kui paljude põlvkondade jooksul ümbritsevad taimeliiki teatud identiteediga naabrid. Minu doktoritöö aluseks oli meeskonnatöö, milles uuriti seitset Eesti poollooduslikku niitu ja viidi läbi suur potikatse. Töörühma liikmena leidsin, et uuritaval taimeliigil on suurim plastilisus kui kaks naabritüüpi (liigikaaslased ja teise liigi esindajad, sugulased ja mittesugulased) on koosluses tavalised ja ümbritsevad liiki sarnase sagedusega. Samuti leidsin, et taimed võivad hoiduda konkurentsist lähisugulastega ja olla mittesugulaste suhtes agressiivsemad. Siiski rohumaa liikide seas pole sugulaste äratundmist lihtne tuvastada. Selle ilmnemine sõltub paljudest tegurites, sealhulgas naabrite kasvutihedusest. Katsest selgus, et taimede konkurentne käitumine teisest liigist naabrite suhtes oli seotud liigi paljunemis- ja levimisstrateegiaga. Seemnetega paljunevad ja kaugele levivad liigid (näiteks liblikõielised) omasid tugevamat konkurentsivõimet. Samas vegetatiivselt paljunevad liigid, mis paigutavad tütarvõsusid lähestikku ja enamasti puutuvad kokku sama liigi esindajatega, olid teiste liikide suhtes nõrgad konkurendid. Kokkuvõtvalt võib öelda, et taimeliigid kasvasid kõige paremini nende naabritega, kellega nad sageli kohtusid oma kodukoosluses. Igal kooslusel on oma kujunemislugu ja evolutsioonilised mehhanismid, mis mõjutavad taimede ruumilist paigutust, konkurentsi ning püsisuhteid naabritega. Taimede võime ära tunda oma naabreid ja reageerida neile rohkem või vähem agressiivsel moel sõltuvalt liigi paljunemisstrateegiast avardab meie arusaamist nende keerukast käitumisest.Plants are sessile organisms and can react to surrounding environment by morphological plasticity. They respond plastically not only to the abiotic environment, but also to the identity of neighbours (individuals of the same or other species, relatives or non-relatives). Plant responses to neighbours are shaped by evolutionary processes as plant species are exposed to the neighbours of a certain identity during many generations. The findings of this thesis are based on the field study of seven semi-natural grasslands in Estonia and pot experiments conducted in a common garden. We found that plants were able to discriminate between different types of neighbours (the same or another species, kin or nonkin) only when these neighbours were common in the plants’ home environment. We also found that plants could avoid competition with kin and show more aggressive behaviour towards nonkin. However, kin recognition is not easy to detect among grassland species, because it may depend on different factors, including the density of neighbours, and can elicit species-specific responses that vary in magnitude and direction. We discovered that plant ability to compete with other species varied with species reproductive strategy and dispersal. Species that reproduce by seed have a low degree of conspecific aggregation in the field (e.g., legumes) and were on average stronger competitors than species that reproduce clonally and form clumps of the same species. As a rule, plants grew better with the neighbour type that they encountered most frequently in nature. Each plant community has its own formation history and is subject to evolutionary processes that shape the patterns of species spatial distribution, neighbour recognition and species co-existence. Plants’ ability to recognize their neighbours and interact with them in a more or less aggressive manner depending on species reproductive strategy expand our understanding of the complexity of plant behaviour

Polyamines and legumes: Joint stories of stress, nitrogen fixation and environment

Polyamines (PAs) are natural aliphatic amines involved in many physiological processes in almost all living organisms, including responses to abiotic stresses and microbial interactions. On other hand, the family Leguminosae constitutes an economically and ecologically key botanical group for humans, being also regarded as the most important protein source for livestock. This review presents the profuse evidence that relates changes in PAs levels during responses to biotic and abiotic stresses in model and cultivable species within Leguminosae and examines the unreviewed information regarding their potential roles in the functioning of symbiotic interactions with nitrogen-fixing bacteria and arbuscular mycorrhizae in this family. As linking plant physiological behavior with “big data” available in “omics” is an essential step to improve our understanding of legumes responses to global change, we also examined integrative MultiOmics approaches available to decrypt the interface legumes-PAs-abiotic and biotic stress interactions. These approaches are expected to accelerate the identification of stress tolerant phenotypes and the design of new biotechnological strategies to increase their yield and adaptation to marginal environments, making better use of available plant genetic resources.Fil: Menendez, Ana Bernardina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Biodiversidad y Biología Experimental; Argentina. Universidad Nacional de San Martin. Instituto Tecnologico de Chascomus. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Conicet - la Plata. Instituto Tecnologico de Chascomus.; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Calzadilla, Pablo Ignacio. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Sansberro, Pedro Alfonso. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Espasandin, Fabiana Daniela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Nordeste. Instituto de Botánica del Nordeste. Universidad Nacional del Nordeste. Facultad de Ciencias Agrarias. Instituto de Botánica del Nordeste; ArgentinaFil: Gázquez, Ayelén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Bordenave, César Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Maiale, Santiago Javier. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Rodriguez, Andres Alberto. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Maguire, Vanina Giselle. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Campestre, Maria Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Gárriz, Andrés. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Rossi, Franco Rubén. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Romero, Fernando Matias. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Solmi, Leandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); ArgentinaFil: Salloum, Maria Soraya. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Fisiología y Recursos Genéticos Vegetales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Monteoliva, Mariela Inés. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Fisiología y Recursos Genéticos Vegetales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Debat, Humberto Julio. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Ruiz, Oscar Adolfo. Instituto Nacional de Tecnología Agropecuaria. Centro de Investigaciones Agropecuarias. Instituto de Patología Vegetal; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús). Universidad Nacional de San Martín. Instituto de Investigaciones Biotecnológicas. Instituto de Investigaciones Biotecnológicas "Dr. Raúl Alfonsín" (sede Chascomús); Argentin

Phytoremediation of hydrocarbon-contaminated soil using plants adapted to the western Canadian climate

As hydrocarbon contaminated sites occur throughout Canada, and are threats to ecosystem and human health, techniques to remediate them are needed. Phytoremediation is the use of plants and their associated microorganisms to degrade, sequester or contain contaminants in soil. This technique is gaining in popularity due to low cost and minimal soil disturbance. However, there are several barriers to implementation of phytoremediation biotechnology in Canada. Only a few species of plants that are native or non-native in Canada have been tested for hydrocarbon tolerance and/or degradation ability. Furthermore, the reason why some plants are more tolerant of hydrocarbons than others, and whether tolerant species also increase hydrocarbon degradation is still unknown. A series of experiments were executed to examine hydrocarbon tolerance in plants including botanical field surveys and growth chamber experiments. Contaminated field plots had significantly higher soil pH, carbon to nitrogen ratio and bare ground, and lower total nitrogen, available phosphorus and litter cover. Mean diversity was 0.52 at the uncontaminated and 0.45 at the contaminated plots even though species richness was similar. Mean species similarity between contaminated and uncontaminated plots was only 31.1 % and cover similarity 22.2%. The most common species observed on contaminated field soil were kochia (Kochia scoparia (L.) Schrad.), wild barley (Hordeumjubatum L.), salt grass (Distichlis stricta (Torr.) Rydb.), Canbyi bluegrass (Poa canbyi (Scribn.) Piper), western wheatgrass (Agropyron smithii Rydb.) and slender wheatgrass (A. trachycaulum var. trachycaulum (Link) Malte). Species that were non-native, non-mycorrhizal, annual, biennial, large seeded and that reproduced by seed only were significantly more common on contaminated plots. Species that were non-mycorrhizal, self-pollinated, large seeded and that reproduced by seed only formed significantly more plant cover on contaminated plots, while woody species and those with unassisted or bird-dispersed seeds formed less. The species with the highest survival after five weeks in a variety of crude oil ­contaminated soils included one native and four non-native grasses, two native and three non-native legumes and two native forbs. All plants grown in potting soil contaminated with 5,000, 10,000 and 50,000 ppm crude oil had significantly lower total biomass and relative growth rates (RGR) compared to the control except Indian breadroot (Psoralea esculenta Pursh). As the crude oil concentration increased from 5,000 to 50,000 ppm total biomass became more strongly negatively correlated (from r=-0.674 to r=-0.939) with RGR. In hydrocarbon-contaminated field soil, total biomass and RGR of eight species with seed masses covering four orders of magnitude were significantly lower than in uncontaminated soil. Both seed size (r=0.976) and RGR (r=-0.916) were strongly correlated with performance in hydrocarbon-contaminated field soil. Those species with large seeds and slow RGR were more tolerant than species with small seeds and high RGR. The two most tolerant species were Indian breadroot and crested wheatgrass (A. pectiniforme R. & S.). After 16 weeks of growth crested wheatgrass was a better hydrocarbon degrader than Indian breadroot as the quantity of five unidentified hydrocarbons was significantly lower in the rhizosphere soil of the former species. When these two species were grown together in the same pot, individual crested wheatgrass plants produced 16 mg more biomass on average than when grown in single species pots, suggesting that interplanting a legume and a grass benefits growth. Hydrocarbon tolerance in plants was related to resource use. Plants possessing stress-tolerant traits performed better on hydrocarbon-contaminated soil than those species with competitive or ruderal traits. This is because the soil of contaminated sites had low fertility and/or adverse soil chemistry. The most tolerant species were not necessarily good at hydrocarbon degradation

Développement d'un mélange d'hydro-ensemencement herbacé pour la phytorestauration de résidus miniers aurifères

Du biochar, de l’hydrogel et des symbiotes végétaux ont été testés comme amendements et biostimulants pour la croissance végétale de Festuca rubra, Trifolium repens L et Avena sativa L hydro-ensemencées sur des résidus aurifères fins et des roches stériles. Un essai de germination indique que les deux biochars ont favorisé la germination des plantes entre 61% et 91%, sauf dans le cas d’une combinaison du biochar BQ-Érable-500-3 avec le trèfle blanc. Une première expérience consistait en trois doses d’hydrogel (0g/kg, 10g/kg, 15g/kg de substrats) combinées avec 0% ou 15% v/v de biochar BQ-Érable-500-3 sur la croissance de A. sativa, F. rubra et T. repens hydro-ensemencées sur ces résidus en conditions contrôlées. L’ajout d’hydrogel avec du biochar a augmenté entre 20% et 27% la biomasse par rapport au témoin sans biochar. L’addition de biochar BQ-Érable-500-3 à 15% v/v aux résidus miniers n’a pas eu d’effets sur les biomasses aériennes et totales des plantes dans le mésocosme. Une interaction a été observée entre l’hydrogel et le biochar. Cependant, celle-ci a été négativement influencée par le taux élevé de biochar appliqué. Dans une deuxième expérience, les effets interactifs de deux biochars avec 15% v/v ou sans biochar (0%) et d’un consortium microbien constitué de deux souches de bactérie fixatrice d’azote (Rhizobium leguminosarum biovar trifoli FH345K et Rhizobium leguminosarum biovar trifoli USDA2046), une souche de bactérie fixatrice libre du diazote (Pseudomonas putida MBN 0213) et une souche de champignon mycorhizien arbusculaire (AMF) (Rhizophagus irregularis DAOM 197198) ont été observés en utilisant des mésocosmes en serre. Le biochar fait avec des écorces d’érable à 7000C a augmenté de 20% la masse totale des plantes comparativement au traitement sans biochar, mais pas avec l’autre biochar fait avec 75% de bois et d’écorces d’érable à 5000C. Il n’y avait pas d’interaction entre le biochar et le consortium microbien. Les deux mélanges végétaux avaient la même biomasse aérienne totale malgré un ratio de population de chaque espèce différente. Par conséquent, l’hydrogel et le biochar seraient bénéfiques pour la croissance végétale, avec l’un ou l’autre des mélanges végétaux, dans des milieux de croissance difficiles pour les plantes tels que les résidus miniers. Par contre, l’effet du biochar sur la croissance dépend du type de biochar. Mots clés : biochar, restauration minière, hydrogel, exploitation aurifère, Avena sativa, Trifolium repens L, Festuca rubraBiochar, hydrogel and plant symbionts were tested as amendments and biostimulants for plant growth of Festuca rubra, Trifolium repens L and Avena sativa L hydro-seeded on gold mine fine tailings and waste rock. A germination test indicated that both biochars favored plant germination between 61% and 91%, except for combination BQ-Érable-500-3with white clover. A first experiment consisting of three hydrogel doses (0 g/kg, 10 g/kg, 15 g/kg of substrate) combined with 0% or 15% v / v of biochar was conducted on the growth of hydro-seeded A. sativa, F. rubra and T. repens planted together on these gold mine tailings under controlled conditions. The addition of hydrogel to biochar increased plant biomass between 20% and 27% compared to the control without biochar. The addition of biochar at 15% v/v to tailings had no effects on the aboveground and total biomass of plants in the mesocosm experiment. An interaction was observed between the hydrogel and the biochar. However, this interaction was negatively influenced by the high rate of biochar applied. In a second experiment, the interaction of both biochars with 15% v/v or without biochar (0%) and of a microbial consortium including two dinitrogen fixing symbiotic bacteria strains (Rhizobium leguminosarum biovar trifoli FH345K and Rhizobium leguminosarum biovar trifoli USDA2046), a free-free-living dinitrogen-fixing bacteria strain (Pseudomonas putida MBN 0213) and a fungal strain of arbuscular mycorrhizal (AMF) (Rhizophagus irregularis DAOM 197198) were observed in mesocosm greenhouse experiment. Biochar made with maple bark at 7000C increased plant biomass by 20% compared to treatment without biochar, but the other biochar made of 75% of wood and bark maple at 500 0C did not influence growth. There was no interaction between biochar and the microbial consortium. Despite their differences in individual biomass, the two plant mixtures did not behave differently in terms of total above ground biomass. These results suggest that hydrogel and biochar are beneficial for plant growth, with either of the plant mixtures, in environments difficult for plants growth such as tailings. On the other hand, the effect of biochar on plant growth depends of the biochar type. Keywords: Biochar, mine reclamation, hydrogel, gold mining, Avena sativa, Trifolium repens, Festuca rubr

Taimkattemuutused luhtadel: niitmise ja jõesetete ladestamise mõju

Väitekirja elektrooniline versioon ei sisalda publikatsioone.Lamminiidud ehk luhad on jõeäärsed, kevadise suurveega üleujutatavad niidud. Oma viljaka mulla ja lopsaka taimekasvu tõttu on nad ajalooliselt olnud väärtuslikud heinamaad. Tänapäeval ohustab Eesti luhtade elurikkust niitmise lakkamine ja sellele järgnev võsastumine. Võsastunud luhad muutuvad sobimatuks nii niidutaimedele kui ka mitmetele luhaga seotud linnuliikidele ning luhal kudevatele kaladele. Oma doktoritöös uurisin, kuidas paarkümmend aastat hooldamata ja osaliselt võsastunud luhtadel taimkate taastub, kui niitmist taas alustada. Niitmine muudab taimkatte madalamaks ning loob paremad valgustingimused madalakasvulistele taimedele, kes ilma inimese abita kõrgekasvulistega konkureerida ei suuda ning niidult kaovad. Leidsin, et kümneaastase niitmise järel soontaimede liigirohkus taastatud luhtadel suurenes, ja seda eelkõige kuivemates taimekooslustes. Liigirikkuse tõusu tagas niitmise ja heina koristamisega kaasnev taimse varise ehk kulu eemaldamine, mille mõju oli olulisem kui heinaga luhast väljakantavate toitainete oma. Ühel multšitaval uurimisalal (hein hekseldati ja jäeti maha) langes väiksekasvuliste rohundite arvukus madalamale kui hooldamata alal – see on üks võimalik tõestus antud hooldamisvõtte sobimatusest. Hooldamisefektiivsuse hindamiseks pakkusin välja ka mitmeid indikaatorliike ehk taimi, kelle esinemine luhaniidul viitab kas hooldatud või hooldamata aladele. Lisaks maapealsele taimestikule uurisin ka luhamullas olevaid taimeseemneid, sest mulla seemnepank võib mõnel puhul niitude taastamisel oluline olla. Leidsin, et ka 25 aastat hooldamata olnud luhtadel moodustub seemnepank kahe kolmandiku ulatuses luhtadele omastest niiduliikidest, mis julgustab luhaniitude taastamisel enam tähelepanu pöörama ka mullas leiduvatele seemnetele. Loodusliku ülejutusrežiimiga luhtadel on väga oluliseks taimeleviste kandjaks ka vooluvesi, mis ühe aastaga tõi uurimisaladele 85 taimeliiki, keda seal enne ei esinenud. Doktoritöö näitas, et luhaniitude taastamiseks on Eesti oludes olemas piisavalt taimeliikide leviseid nii taimkattes kui mullas ning üleujutusvesi on liikidele oluline levikuvektor. Kohane hooldamine koos heina äraveoga tagab luhtadel mitmekesise taimkatte ja aitab säilitada väärtuslikke ökosüsteeme.Floodplain meadows are riverside grasslands inundated during spring floods. Valued due to their lush vegetation, they were traditionally mown for animal fodder. At present, Estonian floodplain meadows are threatened by management cessation and consecutive shrub encroachment. Meadows covered by shrubs are unsuitable habitats for grassland plants, several floodplain-related birds and for fish that spawn on the floodplain. In my thesis I focused on the vegetation dynamics of floodplain meadows where mowing was re-started after two decades of abandonment. Mowing lowers the vegetation height and provides better light conditions for small statured plant species that would otherwise be out-competed by taller plants in competition for light. I found that the species diversity increased after ten years of management, the changes being more pronounced in relatively drier of the studied plant communities. The effect of management was mediated by litter removal which was more important in explaining changes in species richness than the amount of nutrients carried out of the meadow by hay harvesting. The proportion of small herbs unexpectedly decreased in one of the study sites that was managed by mulching (hay left on ground). This might indicate that mulching is an inappropriate means of management. To assess the management status of a meadow, I proposed several management indicator species. In addition to the vegetation, I also studied soil seed bank which could contribute to grassland restoration. I discovered that in the soil seed bank of meadows abandoned for 25 years, two thirds of the species present were typical to floodplain meadows. This can encourage nature managers to use also the soil seed banks in restoration of floodplain meadows. The naturally meandering rivers with un-altered flooding regime also proved efficient vectors for plant dispersal, carrying in 85 new species to the study sites during one year. The thesis demonstrate that Estonian floodplain grasslands still harbour a viable propagule pool both above- and belowground for floodplain meadow restoration, and that rivers can facilitate plant dispersal. Proper management with hay harvesting can support a diverse vegetation and maintain the complex ecosystem of floodplain meadows

Timing of weed control and harvest date effects on potato crop field performance and mineral content.

Masters Degree. University of KwaZulu-Natal, Pietermaritzburg.Potato (Solanum tuberosum) is an important vegetable crop that is high on dietary minerals and vitamins that are needed by the human body but can be a weak competitor to weeds. The aim of the study was to determine the effect of weeds and harvest period on plant growth, yield and mineral content of tubers. The experiment was conducted at the University of KwaZulu-Natal’s Ukulinga farm. The experiment had three weeding treatments namely control weed free, weed free till flowering stage then stop and no weeding. And two harvest periods which were early (90 days after planting) and late (120 days after planting). The crop was monitored from emergence using phenological (plant height and leaf number) and physiological (Leaf area index, Chlorophyll content index, photosynthetically active radiation, stomatal conductance) parameters during the growing stage prior to flowering. At harvest, the number of tubers, size of tubers and plant biomass were recorded to determine the yield. After yield determination the potato samples were taken to the laboratory for mineral content analysis. The results showed that there was a significant difference (p<0.05) in the weeding treatments with respect to the phenological parameters. The control weed free treatment had the highest plant growth and yield while the no weeding treatment had the lowest plant growth and yield. It was also observed that the early harvested tubers were smaller in size while the tubers harvested late were larger in size. This is because the tubers harvested late were given enough time to grow and mature. Harvesting early under the no weeding treatment resulted in significantly lower yields due to the decrease in tuber mass. There were significant effects of weed control and harvest timings with respect to mineral content in tubers. Potassium was found to be the dominant mineral element followed by phosphorus. These elements were found in levels that were up to 100 times higher than those of calcium, magnesium and sodium in potato tubers. It is concluded that delaying weed control reduces crop performance, yield and mineral content. However, delaying harvest time may provide an opportunity for the crop to accumulate more weight and mineral content in the tubers. Keywords: Chlorophyll content index, Tubers, Biomass, Leaf area index, Photosynthetically active radiation, mineral content, yield

Carotenoids in Fresh and Processed Food: Between Biosynthesis and Degradation

Carotenoids are uniquely functional polyene pigments that are ubiquitous in nature; aside from being responsible for the color of a wide variety of vegetables, interest has been focused on food carotenoids due to their likely health benefits. This Special Issue, “Carotenoids in Fresh and Processed Food: Between Biosynthesis and Degradation”, consists of five peer-reviewed papers that cover a numerous new insights on the chemistry of carotenoids together with some observations related to their protection from photodegradation. Moreover, other considerations about their biosynthesis and influencing parameters in fresh food are included

Potential Allelopathic Effect of Species of the Asteraceae Family and Its Use in Agriculture

Some species are capable of producing substances that affect seed germination, stimulating, or retarding this process, and can also suppress the development of other plants, acting as an antagonistic plant. This can occur naturally, through the release of exudates, or through the action of essential oil, extracts obtained from different parts of the plant, or plant residues with potential allelopathic action. The aim of this chapter is to present the main plant genera of the Asteraceae family with potential phytotoxic or allelopathic activity, with a suppressive effect on the growth of herbicide-tolerant weeds. The genus defined were Acmella, Artemisia, and Bidens, highlighting the form of use—plant extract, essential oil, or plant residues. The Asteraceae family is considered a repository of species to be explored for allelopathy with several associated secondary metabolites such as terpenes, saponins, alkaloids, alkamides, cinnamic acid derivatives, and flavonoids. In addition to these, for the genus Bidens, the presence of the acetylenic compound phenylheptatriine (PHT) is considered an important allelochemical with potent allelopathic action. The presence of this compound is associated with the cytotoxic activity of representatives of this genus, which can be a source of prospecting for new molecules to be used as bioherbicides