Nitrogen (N), an essential plant macronutrient, is among the most limiting factors of crop yield. To sustain modern agriculture, N is often amended in soil in the form of chemical N fertilizer, a major anthropogenic contributor to nutrient pollution that affects climate, biodiversity and human health. To achieve agricultural sustainability, a comprehensive understanding of the regulation of N response in plants is required, in order to engineer crops with higher N use efficiency. Recently, epigenetic mechanisms, such as histone modifications, have gained increasing importance as a new layer of regulation of biological processes. However, our understanding of how epigenetic processes regulate N uptake and assimilation is still in its infancy. To fill this knowledge gap, we first performed a meta-analysis that combined functional genomics and network inference approaches to identify a set of N-responsive epigenetic regulators and predict their effects in regulating epigenome and transcriptome during plant N response. Our analysis suggested that histone modifications could serve as a regulatory mechanism underlying the global transcriptomic reprogramming during plant N response. To test this hypothesis, I applied chromatin immunoprecipitation-sequencing (ChIP-Seq) to monitor the genome-wide changes of four histone marks (H3K27ac, H3K4me3, H3K36me3 and H3K27me3) in response to N supply in tomato plants, followed by RNA-Seq to profile the transcriptomic changes. To investigate the organ specificity of histone modifications, I assayed shoots and roots separately. My results suggest that up to two-thirds of differentially expressed genes (DEGs) are modified in at least one of the four histone marks, supporting an integral role of histone modification in regulating N response. I observed a synergistic modification of active histone marks (H3K27ac, H3K4me3 and H3K36me3) at gene loci functionally relevant to N uptake and assimilation. Surprisingly, I uncovered a non-canonical role of H3K27me3, which is conventionally associated with repressed genes, in modulating active gene expression. Interestingly, such regulatory role of H3K27me3 is specifically associated with highly expressed genes or low expressed genes, depending on the organ context. Overall, I revealed the multi-faceted role of histone marks in mediating the plant N response, which will guide breeding and engineering of better crops with higher N use efficiency

This diploma thesis deals with a utilization of school gardens for education at primary schools. It draws on historical development of school gardens and tries to emphasize an importance of their incorporation into an educational process, their positive impact on health and growth of pupils, and improvement of their skills and knowledge. Thesis also analyses relationships with Framework Education Programme for Elementary Education. Research itself deals with current state and utilization of school gardens by primary school teachers at Kolin district. It focuses on a school garden ownership, frequency of their usage, personal experience and needs of teachers for giving lectures in gardens. It also discusses areas of education for which the gardens are mostly used. Keywords School garden, natural garden, natural classroom, environmental education, human alientation from nature, Horticultural Therapy, Framework Education Programme for Elementary Education, teaching

There is at present a growing concern and awareness of the endangered status of many indigenous South African plants in the wild, a number of which have potential for commercial production. One such example is Gladiolus scabridus, a vulnerable species endemic to the mountains of northern KwaZulu-Natal and southern Swaziland. It has considerable potential due to its floral characteristics. However, little is known about its horticultural requirements. Thus propagation and cultural practices were investigated with the aim of both conservation and commercialisation of the species. The ideal conditions for G. scabridus seed germination were determined. The presence or absence of light had no significant effect. Optimum germination was achieved at 20 QC of both winged and dewinged seeds. Higher temperatures appear to have a negative effect on germination and none of the winged seeds germinated at 30 QC. Under ideal conditions, fresh seed showed significantly higher vigour and viability than stored seed although the germination of stored seed was hampered by a higher internal fungal content. Successful tissue culture protocol was established for G. scabridus axillary bud and cormel halve explants. During the initial shoot initiation and proliferation stages (stage I and 11), the significantly higher shoot numbers occurred in the absence of growth regulators in both explant types. However, shoots with 1.0 mg 1 -1 6-benzyl-amino-purine (BAP) and 0.5 mg 1 -1 1-naphthalene-acetic-acid (NAA) were healthier in appearance. Higher levels of 5.0 mg 1 -1 NAA inhibited shoot production and encouraged root development in cormel halve explants. During stage 11, axillary bud explants showed root and cormlet development. More roots were initiated without growth regulators, whilst 5.0 mg 1 -1 NAA resulted in significantly better cormlet development. Shoot and cormlet growth of cormel halve explants during stage II was not significantly affected by the presence or absence of NAA and BAP. Significantly more roots were produced with 5.0 mg 1 -1 NAA. During stage III (rooting), the presence of activated charcoal (AC) was essential for the initiation and development of roots in vitro. Root and cormlet development in all explant types was significantly affected by the interaction between the previous treatments from stages I and 11 and the new treatments. During stage IV (hardening off) , most explants died down in the hardening off media leaving resting cormlets. There was a significant interaction between 1.0 mg 1 -1 NAA and 0.3 % AC from stage III, resulting in significantly more cormlets in both axillary bud and cormel halve explants. There was successful cormlet growth after cold storage which is advantageous in reducing the need for acclimatization. G. scabridus corms were successfully forced out of their normal flowering period. Temperatures of 10,5.5 and 2 QC showed successful corm initiation although the corms need to be stored for longer at warmer temperatures. It is suggested that a treatment of 2 QC for 6 weeks is the optimal condition for forcing G. scabridus corms. Although originating from a stressful environment, G. scabridus appears to show capacities for improved growth under controlled conditions. Fertilizer applications enhanced growth and reduced the time to flowering. Nitrogen (N) was found to be important for vegetative growth, flowering and daughter corm development, whereas potassium (K) influenced cormel production. Fertilizer with higher N and lower K is appropriate for the beginning and middle of the growing season and then adjusted to a lower N and higher K fertilizer to promote cormel formation. G. scabridus was found to produce prolific numbers of cormels which is an important source of plant material. Mineral leaf analysis showed that optimum levels for wild species are lower than those for hybrid gladioli with the optimum levels affected by physiological corm maturity and subsequent plant growth. Norms for postharvest handling of cut G. scabridus spikes have been developed. Spikes held in 2 % sucrose had a longer vase life and better floret opening and quality than those kept in distilled water, Prolong, Chrysal, 2 % sucrose and 2 % ethanol, 1 % sucrose, 4 % sucrose, 1 % sucrose and 0.5 % JIK, 2 % sucrose and 0.5 % JIK and 4 % sucrose and 0.5 % JIK, 2 % fructose and 2 % glucose. The use of commercially available solutions should be used with caution. Florets produced a climacteric-like CO2 peak, but levels of ethylene were unmeasurable. Cold storage and the use of polypropylene sleeves delays senescence. G. scabridus spikes secrete droplets of a sticky substance which was confirmed to be extra floral nectar through HPLC analysis. Market research revealed a positive response to the species from consumers and retailers alike with potential for cultivation as a cut flower and bedding plant. However, the cost will determine supply and demand. A field study conducted at Bivane Dam, northern KwaZulu-Natal, confirmed that G. scabridus colonies prevail in rocky, quartzite outcrops where they become wedged between the rocks. Plants were found at different stages of development with populations of not more than 108 plants per colony. Soil data of G. scabridus sites was compared to that of two sites nearby. It was found that G. scabridus soils are higher in phosphorus (P), zinc (Zn) and organic carbon. Leaf analysis confirmed that they have adapted their growth to low nutrient levels. The G. scabridus studies have clearly shown that the species can be successfully moved from a wild plant to a commercially viable one and in so doing its conservation status can also be improved. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.

Integrated aquaponic food production systems are capable of producing more food on less land using less water than conventional food systems, and marine systems offer the potential of conserving freshwater resources. However, critical factors such as suitable species combinations, environmental conditions (salinity and pH), and nutrient management (animal to plant ratio, C/N ratio, and dietary crude protein) have not been fully understood for marine systems. There were four objectives in this project. The first objective was to evaluate the growth performance of potential comparable combination (whiteleg shrimp with three halophytic plants) for the development of marine aquaponics with BFT under different salinities. The second objective was to evaluate stocking densities and the C/N ratio on growth and production of whiteleg shrimp and three halophytes. The third objective was evaluation of varying concentrations of dietary crude protein in practical diets fed to shrimp raised in biofloc aquaponic saltwater systems. The fourth objective was to evaluate effects of pH levels and additional C on the growth and production of whiteleg shrimp and five plant species in marine aquaponics. Four conclusions were determined: 1) Regarding marine aquaponics, whiteleg shrimp and the three halophytes (Atriplex hortensis, Salsola komarovii, and Plantago coronopus) are suitable combinations for future development. According to the research results, shrimp performed better in a salinity of 15 and 20 ppt; yet, plants performed better in a salinity of 10 and 15 ppt. Therefore, a salinity of 15 ppt is suggested as the optimal saline condition for shrimp and the three halophytes in an indoor marine aquaponics system. In addition, inoculating probiotics do have the efficiency of stabilizing water quality, cultivating microbial community, and enhancing the health of shrimp and plants in the operation of aquaponics. 2) The stocking density ratio and C/N ratio exerted significant impacts on the performance of shrimp and plants in marine aquaponics. Shrimp performed better with the stocking density of 2:1 and 3:1, with no impact from the C/N ratio. Conversely, plants performed better with the stocking density of 3:1 and 5:1 with the C/N ratio at 15. Therefore, a stocking density ratio of 3:1 with a C/N ratio at 15 is suggested as the optimal condition for shrimp and the three halophytes in an indoor marine aquaponic food production system. Inoculating the water with biofloc and applying probiotics regularly can enhance the management of water quality and the health of shrimp and plants in aquaponics. 3) Among the findings of the study, shrimp growth was not affected by the protein content of the feed, suggesting that it is possible to use feeds with lower protein concentration when culturing shrimp in biofloc-based marine aquaponics. However, plants grew better in the treatments with higher protein content feed in the early and middle stages of production. Hence, for maximum production, providing a higher protein concentration feed (35 %) in the early stages of system start-up, and switching to a lower protein concentration feed (30 %) in the later stages of cultivation might be feasible. 4) The current study found no significant effects of pH or additional C on shrimp performance. In contrast, plants grew better in lower pH treatments, while additional C supplements improved the performance of plants grown in higher pH treatments and had similar results to the lower pH treatments. We suggest that RO water is not suitable source of water for shrimp-based marine aquaponics if ionic composition is not managed. The addition of C, however, led to improved growth and yields of most plants. Hence, adding C can be a promising approach in marine aquaponics to enhance the resistance to the abiotic stress of plants and improve their growth.<div> <br>The present study on marine aquaponics has produced important findings that will fill some knowledge gaps, provide management guidelines for production, and facilitate its development. <br></div>

Tesis por compendio / [ES] La agricultura moderna enfrenta un doble desafío, garantizar la seguridad alimentaria mundial y ejecutarla de manera sostenible. Se prevé que la población mundial seguirá creciendo durante las próximas tres décadas, hasta alcanzar aproximadamente 10×109 personas en 2050. Sin embargo, el estrés por salinidad plantea un peligro importante no solo en la degradación del suelo sino además para el crecimiento, desarrollo y rendimiento de diversos cultivos, poniendo en riesgo la alimentación mundial; siendo considerado como uno de los agentes más dañinos para el ciclo de vida de la planta. Actualmente, entre el 20% y el 30% de la tierra cultivable en todo el mundo está afectada por la salinidad, y se estima que para 2050 el área afectada superará el 50%. Situación que ha empeorado a lo largo de los años debido al impacto del cambio climático acelerado. Generalmente, la mayoría de los cultivos hortícolas son altamente susceptibles a la salinidad, con un umbral no mayor a 2 dS m-1. Estos cultivos están conformados por una amplia gama de especies de gran importancia para la alimentación humana. El tomate (Solanum lycopersicum L.) y la lechuga (Lactuca sativa L.), son cultivos hortícolas de alto valor para la economía y el consumo de la humanidad. La producción de tomate en el mundo asciende a más de 182 millones de toneladas y de lechuga a más de 29 millones. Sin embargo, el estrés salino provoca una reducción significativa en el desarrollo de estos cultivos y una pérdida de rendimiento a través del estrés iónico, osmótico y oxidativo. En los últimos años, los productos bioestimulantes han sido reconocidos como herramientas agronómicas innovadoras para generar sistemas sostenibles, mejorando la productividad agrícola, el rendimiento, la salud de las plantas y la tolerancia a factores de estrés como la salinidad. Prueba de ello es el aumento de las publicaciones científicas y la constante expansión de su mercado. De hecho, los bioestimulantes afectan positivamente el metabolismo de las plantas en condiciones ambientales óptimas y subóptimas. Sin embargo, los procesos que desencadenan los bioestimulantes suelen ser difíciles de identificar y todavía están en estudio. Por tanto, es crucial evaluar los mecanismos de acción de los bioestimulantes en diferentes condiciones experimentales, como se ha realizado en el presente estudio. El estudio presenta dos objetivos, un principal: Determinar la influencia de la aplicación de dos formulaciones del bioestimulante BALOX® sobre los mecanismos de tolerancia al estrés osmótico, iónico y oxidativo causado por el exceso de sales solubles en cultivos hortícolas; y un objetivo secundario: Evaluar los efectos de la aplicación del producto bioestimulante BALOX® sobre la mejora de la calidad de distintos suelos tanto en condiciones no salinas como salinas. Para alcanzar el primer objetivo, se evaluó el impacto de dos formulaciones y diferentes dosis del bioestimulante y se analizaron diversos parámetros biométricos de las plantas de tomate y lechuga, y múltiples marcadores bioquímicos de estrés, como pigmentos fotosintéticos, concentraciones de iones en raíces y hojas, contenidos foliares de diferentes osmolitos, marcadores de estrés oxidativo, y compuestos antioxidantes, así como la actividad específica de diversas enzimas antioxidantes, en plantas sometidas a la combinación de diversos niveles de salinidad del agua de riego y del suelo en distintas clases texturales. Respecto al segundo objetivo, se estudió el efecto del bioestimulante en la mejora de la calidad del suelo, que es el medio que sustenta el sistema radicular. Para ello, se analizaron varias propiedades físicas (estabilidad de los agregados, densidad aparente y porcentaje de porosidad) y químicas (conductividad eléctrica, capacidad de intercambio catiónico y materia orgánica) del suelo. Además, se determinaron diferentes parámetros del sistema radicular y foliar de plantas de S. lycopersicum... / [CA] L'agricultura moderna enfronta un doble desafiament, garantir la seguretat alimentària mundial i executar-la de manera sostenible. Es preveu que la població mundial continuarà creixent durant les pròximes tres dècades, fins a aconseguir aproximadament 10×109 persones en 2050. No obstant això, l'estrés per salinitat planteja un perill important no sols en la degradació del sòl sinó a més per al creixement, desenvolupament i rendiment de diversos cultius, posant en risc l'alimentació mundial; sent considerat com un dels agents més nocius per al cicle de vida de la planta. Actualment, entre el 20% i el 30% de la terra cultivable a tot el món està afectada per la salinitat, i s'estima que per a 2050 l'àrea afectada superarà el 50%. Situació que ha empitjorat al llarg dels anys a causa de l'impacte del canvi climàtic accelerat. Generalment, la majoria dels cultius hortícoles són altament susceptibles a la salinitat, amb un límit no major a 2 dS m-1. Estos cultius estan conformats per una àmplia gamma d'espècies de gran importància per a l'alimentació humana. La tomaca (Solanum lycopersicum L.) i l'encisam (Lactuca sativa L.), són cultius hortícoles de gran importància per a l'economia i el consum de la humanitat. La producció de tomaca en el món ascendix a més de 182 milions de tones i l'encisam a més de 29 milions. No obstant això, l'estrés salí provoca una reducció significativa en el desenvolupament d'estos cultius i una pèrdua de rendiment a través de l'estrés iònic, osmòtic i oxidatiu. En els últims anys, els productes biostimulants han sigut reconeguts com a ferramentes agronòmiques innovadores per a generar sistemes sostenibles, millorant la productivitat agrícola, el rendiment, la salut de les plantes i la tolerància a factors d'estrés com la salinitat. Prova d'això és l'augment de les publicacions científiques i la constant expansió del seu mercat. De fet, els biostimulants afecten positivament el metabolisme de les plantes en condicions ambientals òptimes i subòptimes. No obstant això, els processos que desencadenen els biostimulants solen ser difícils d'identificar i encara estan en estudi. Per tant, és crucial avaluar els mecanismes d'acció dels biostimulants en diferents condicions experimentals, com s'ha realitzat en el present estudi. L'estudi presenta dos objectius, un principal: Determinar la influència de l'aplicació de dos formulacions del biostimulant BALOX® sobre mecanismes de tolerància a l'estrés osmòtic, iònic i oxidatiu causat per l'excés de sals solubles en cultius hortícoles; i un objectiu secundari: Avaluar els efectes de l'aplicació del producte biostimulant BALOX® sobre la millora de la qualitat de diferents sòls tant en condicions no salines com salines. Per a aconseguir el primer objectiu, es va avaluar l'impacte de dos formulacions i diferents dosis del biostimulant i es va analitzar diversos paràmetres biomètrics de les plantes de tomaca i encisam, i múltiples marcadors bioquímics d'estrés, com a pigments fotosintètics, concentracions d'ions en arrels i fulles, continguts foliars de diferents osmolits, marcadors d'estrés oxidatiu, l'activitat específica de diversos antioxidants enzimàtics i compostos antioxidants, en plantes sotmeses a la combinació de diversos nivells de salinitat de l'aigua de reg i del sòl en diferents classes texturals. Respecte al segon objectiu, es va estudiar l'efecte del biostimulant en la millora de la qualitat del sòl, que és el medi que sustenta el sistema radicular. Per a això, es van analitzar diverses propietats físiques (estabilitat dels agregats, densitat aparent i percentatge de porositat) i químiques (conductivitat elèctrica, capacitat d'intercanvi catiònic i matèria orgànica) del sòl. A més, es van determinar diferents paràmetres del sistema radicular i foliar de plantes de S. lycopersicum. L'aplicació del biostimulant BALOX ® va tindre un efecte global positiu en el creixement de les plantes de tomaca i encisam tractades... / [EN] Modern agriculture faces a double challenge: guaranteeing global food security and executing it in a sustainable manner. The world population is expected to continue growing over the next three decades, reaching approximately 10x109 people in 2050. However, salinity stress poses a significant danger not only to soil degradation but also to the growth, development and yield of various crops, putting global food at risk and being considered one of the most harmful agents for the life cycle of the plant. Currently, between 20% and 30% of arable land worldwide is affected by salinity, and it is estimated that by 2050 the affected area will exceed 50%. A situation that has worsened over the years due to the impact of accelerated climate change. Generally, most horticultural crops are highly susceptible to salinity, with a threshold no greater than 2 dS m-1. These crops comprise a wide range of species of great importance for human nutrition. Tomato (Solanum lycopersicum L.) and lettuce (Lactuca sativa L.) are horticultural crops of great importance for the economy and consumption of humanity. Tomato production in the world amounts to more than 182 million tons, and lettuce production to more than 29 million. However, salt stress causes a significant reduction in the development of these crops and a loss of yield through ionic, osmotic and oxidative stress. In recent years, biostimulant products have been recognized as innovative agronomic tools to generate sustainable systems, improving agricultural productivity, yield, plant health and tolerance to stress factors such as salinity. Proof of this is the increase in scientific publications and the constant expansion of their market. In fact, biostimulants positively affect plant metabolism under optimal and suboptimal environmental conditions. However, the processes triggered by biostimulants are often difficult to identify and are still being studied. Therefore, it is crucial to evaluate the mechanisms of action of biostimulants under different experimental conditions, as has been done in the present study. The study has two objectives: the main one is to determine the influence of the application of two formulations of the biostimulant BALOX® on the tolerance mechanisms to osmotic, ionic and oxidative stress caused by excess soluble salts in horticultural crops; and a secondary objective is to evaluate the effects of the application of the biostimulant product BALOX® on the improvement of the quality of different soils in both non-saline and saline conditions. To achieve the first objective, the impact of two formulations and different doses of the biostimulant was evaluated by analyzing various biometric parameters of tomato and lettuce plants, and multiple biochemical stress markers, such as photosynthetic pigments, ion concentrations in roots and leaves, foliar contents of different osmolytes, oxidative stress biomarkers, and antioxidant compounds, as well as the specific activity of several antioxidant enzymes, in plants subjected to the combination of various salinity levels of irrigation water and soil in different textural classes. Regarding the second objective, the effect of the biostimulant on improving the quality of the soil, which is the medium that supports the root system, was studied. To this end, several physical (aggregate stability, apparent density and percentage of porosity) and chemical (electrical conductivity, cationic exchange capacity and organic matter) properties of the soil were analyzed. In addition, different parameters of the root and leaf system of S. lycopersicum plants were determined. The application of the biostimulant BALOX® had an overall positive effect on the growth of the treated tomato and lettuce plants... / Zuzunaga Rosas, JG. (2024). Evaluación del producto bioestimulante BALOX® como inductor de tolerancia en cultivos hortícolas frente al estrés causado por el exceso de sales solubles en suelos y aguas [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/213213 / Compendio