Soil salinity is a common abiotic stress for plants, that is having an increasing impact on international food production. A practical strategy to help mitigate the adverse effects of salinity stress on crop productivity is to increase salt tolerance of crop plants. It has been shown that exogenous application of L-proline and L-glutamate is capable of reducing the severity of salinity stress on seed germination and early seedling growth of brassica and cucumber, respectively. The main aim of the present study was to investigate the potential of all 20 common protein amino acids to alleviate salinity stress in lettuce (Lactuca sativa L., variety ‘Great Lakes’) during and immediately following germination. Sowing lettuce seeds in different concentrations of sodium chloride (NaCl) adversely affected germination and early seedling growth in a dose-dependent manner. After 48 hours of sowing lettuce seeds in 1 mM of any of the 20 exogenous amino acids in the absence of NaCl, it was found that the amino acids also inhibited seedling growth, particularly root elongation. However, in direct treatment experiments involving addition of seven amino acids singly (L-asparagine, L-isoleucine, L-leucine, L-proline, L-phenylalanine, L-tyrosine and L-valine) to an inhibitory concentration (60mM) of NaCl, it was found that lettuce seedling growth was protected from the salt stress. Additionally, seeds pre-treated for 8 hours before germination with L-arginine, L-glycine, L-histidine, L-methionine and L-phenylalanine, showed significant growth recovery after a further 40 hours growth exposed to 60mM NaCl. The measurements of cell size in root maturation zone and mitotic index at the root tip of lettuce seedlings after 48 hours from sowing seeds suggested that it might be possible that some amino acid treatments could affect cell elongation and / or cell division. However, further in-depth investigations are required and warranted to elucidate the mechanism(s) whereby exogenous amino acids could play a role in alleviation of salt stress in lettuce. It is concluded that several L-amino acids have the potential in pre-sowing seed treatment (seed priming technology) to enhance salt tolerance for crop stand establishment in soils with salinity issues.

Germination of plants is one of the most important stages during their growth which is often influenced by environmental stresses, especially drought and salinity. This study was conducted to investigate the effects of salinity and drought on seed germination and growth of Lathyrus sativa. The experiment was laid out in a completely randomized design with factorial arrangement in 4 replications. Salinity treatments were 0, 2, and 4 dS/m and drought treatments included 0, 0.4, 0.8, 1.2 MPa. Salinity and drought treatments were prepared by using sodium chloride and polyethylene glycol 6000, respectively. The results showed that salinity and drought stresses decreased germination percentage, root and radicle length.

Submitted by Jorge Silva (jorgelmsilva@ufrrj.br) on 2017-09-15T19:31:42Z No. of bitstreams: 1 2016 - Renata Napolis Fonte.pdf: 2644583 bytes, checksum: c2421580b82f9265d2881382fabdf85d (MD5) / Made available in DSpace on 2017-09-15T19:31:42Z (GMT). No. of bitstreams: 1 2016 - Renata Napolis Fonte.pdf: 2644583 bytes, checksum: c2421580b82f9265d2881382fabdf85d (MD5) Previous issue date: 2016-07-29 / CAPES / Corn seed storage is a vital phase, in order to maintain high seed germination and vigor from harvest until planting. There is not many studies dedicated to find substitutes to synthetic fungicides and inseticides. The present study aimed evaluate effects of using plant extracts, diatomaceous powder and a synthetic fungicide, wich main active is captan, associated with osmo and hydropriming in corn (Zea mays L.) seed treatment and storage. Vegetal extracts of pepper (Piper nigrum), garlic (Allium sativum) e tobacco (Nicotiana tabacum) were used, chosen after being reported as owner of antimicrobial properties. Diatomaceous powder has been being used successfully in small farms, basically because it is composed mainly of silica, wich causes dehydration and death of insects of Sitophilus gender, commonly called ?carunchos?. Priming seeds comprehends controlled exposion of water, wich brings positive effects. Three experiments were conducted. In the first experiment, all products were used in the form of powder, in seeds storaged in polyethylene (PET) bottles for ten months. In the second experiment the products were used associated with osmopriming, drying back to a water content near 10%, and the seeds were storaged in PET bottles for 8 months. In the third experiment, all products were used associated with hydropriming, dried back to a water content near 10%, and the seeds were storaged for 8 months. Evaluations were made every two months, measuring the seeds quality through germination test, germination speed index, seedlings length, weight, water content and blotter test during storage period. First experiment was outlined using a factorial design 6x6 (6 products: pepper, garlic and tobacco extracts, diatomaceous powder, synthetic fungicide and control e 6 storage periods: at 0, 2, 4, 6, 8 and 10 months). Second and third experiments were outlined using a factorial design 6x5 (6 products and 5 storage periods). Statistical analisys was performed by Sisvar software, storage periods were analysed using regression and products were submitted to Tukey test (p<0,05). It was observed a reduction in physiological quality of seeds with the advancement of storage, in all experiments performed. The use of the powder pepper extract resulted in the greatest % of germination and first germination count found. Garlic extract associated with osmopriming in seeds treatment resulted in higher values of seeds germinated at the end of storage. The hydropriming associated with the pepper extract resulted in higher values of germination speed index, length of seedlings and seedling dry weight. Regarding sanitary quality, the most frequently found were species of the genera Rhizopus, Penicillium and Fusarium. Fungicide resulted in better control of these pathogens in most analysis, but was overcome by the use of garlic extract associated with osmopriming in control of Rhizopus and Penicillium and was similar to the use of diatomaceous earth and tobacco extract associated with hydropriming in control of Rhizopus. / O armazenamento de sementes de milho ? uma etapa crucial do processo de produ??o e quase sempre obrigat?ria, considerando a diferen?a entre a ?poca de colheita e semeadura posterior. Na produ??o de sementes em cultivo org?nico, n?o existe abund?ncia de trabalhos que estudem alternativas ao uso de inseticidas e funcigidas sint?ticos. O presente trabalho avaliou os efeitos de extratos vegetais, terra diatom?cea e funcigida comercial com captana como princ?pio ativo associados ao condicionamento fisiol?gico no tratamento e armazenamento de sementes de milho (Zea mays L.). Os extratos usados foram de pimenta-do-reino (Piper nigrum L.), alho (Allium sativum L.) e tabaco (Nicotiana tabacum L.), detentores de propriedades antimicrobianas. A terra diatom?cea ? usada com sucesso no armazenamento de sementes na agricultura familiar, no controle de insetos do g?nero Sitophilus, comumente chamados de ?carunchos?. O condicionamento fisiol?gico engloba um conjunto de t?cnicas, que envolvem a exposi??o das sementes ? embebi??o controlada de ?gua, com benef?cios para seu armazenamento. Foram realizados 3 experimentos. No primeiro foram usados os extratos bot?nicos e a terra diatom?cea em p?, em sementes armazenadas em garrafas de polietileno (PET) por dez meses. No segundo, foram usados os mesmos produtos via osmocondicionamento, com posterior secagem at? as sementes atingirem teores de ?gua pr?ximos a 10% e armazenamento por 8 meses. No terceiro, os produtos foram usados via hidrocondicionamento, seguido de secagem at? teores pr?ximos de 10% de ?gua e armazenamento por 8 meses. Foram realizadas avalia??es sobre a qualidade fisiol?gica (testes de germina??o, velocidade de germina??o, comprimento de pl?ntula, massa seca de pl?ntulas e teor de ?gua) e sanit?ria (blotter test) a cada dois meses durante o per?odo de armazenamento. O primeiro experimento foi delineado em esquema fatorial 6x6 (6 produtos: extrato de pimenta-do-reino, alho e tabaco, terra diatom?cea, fungicida comercial e testemunha ? nenhum produto e 6 pontos de avalia??es durante os dez meses de armazenamento). O segundo e terceiro experimento foram delineados em esquema fatorial 6x5 (6 produtos e 5 pontos de avalia??es durante os 8 meses de armazenagem). Os dados foram submetidos ? an?lise estat?stica no programa Sisvar, usando regress?o para per?odos de armazenamento e teste Tukey (p<0,05) para produtos. Foi observada redu??o da qualidade fisiol?gica das sementes com o armazenamento em todos os experimentos realizados. O uso do extrato de pimenta-do-reino em p? resultou nas maiores porcentagens de germina??o e primeira contagem da germina??o. O extrato de alho associado ao osmocondicionamento resultou nos maiores valores de sementes germinadas ao final do armazenamento. O hidrocondicionamento associado ao extrato de pimenta-do-reino resultou nos maiores valores de ?ndice de velocidade de germina??o, comprimento de pl?ntulas e massa seca de pl?ntulas. Em rela??o ? qualidade sanit?ria, foram encontrados com maior frequ?ncia esp?cies dos g?neros Rhizopus, Penicillium e Fusarium. O fungicida apresentou melhores resultados no controle desses pat?genos, na maioria das avalia??es, por?m, foi superado pelo uso do extrato de alho associado ao osmocondicionamento no controle de Rhizopus e Penicillium e foi similar ao uso de terra diatom?cea e extrato de fumo associados ao hidrocondicionamento no controle de Rhizopus.

Thesis (M. Sc. Agriculture (Soil Science)) -- University of Limpopo, 2019 / One of the major constraints to crop productivity in South Africa is crop nutrient deficiency especially micronutrients. Laboratory, glasshouse and field studies were carried out during the 2016/2017 growing season to assess the effects of micronutrient (Zn, B and Mo) seed priming on maize growth and yield in micronutrient deficient soils of the Limpopo province. The laboratory experiment was carried out in a completely randomized design (CRD) laid out in a 3 x 5 x 3 factorial treatment structure with three replications. The assessments of the micronutrients were made at 0%, 0.01%, 0.05%, 0.1%, and 0.5% concentrations. The seeds were primed in the solutions for 24 h, 12 h and 8 h. The glasshouse experiment was carried out in a completely randomized design (CRD) laid out in a 3 x 4 x 2 factorial treatment structure with three replications. In the field, a single factor experiment in a randomised complete block design (RCBD) with three replications and a control was used, with micronutrient concentrations as levels. The laboratory study investigated the effect of seed priming with Zn, Mo and B on germination (germination percentage (GP), germination rate (GR), the coefficient velocity of germination (CVG), days to germination (DG) and mean germination time (MGT)). The interaction between seed priming duration and concentration levels of seeds primed with B had significant effect (P < 0.05) on germination. The interaction between seed priming duration and concentration levels of seeds primed with Zn had significant effect (P < 0.05) on germination. The interaction between seed priming duration and Mo concentration levels on CVG, MGT and DE had no significant different (P > 0.05). Meanwhile, the effect on GP and GR had significant (P < 0.05) effects. Seed priming with the micronutrients and water resulted in improved GP, MGT and CVG for seeds primed with 0.01, 0.05 and 0.1% for 24 h in laboratory conditions. The glasshouse study was established to investigate the effect micronutrient seed priming on seedling establishment and growth. The effects of the interaction between Mo concentration levels and duration, Zn concentration levels and duration, B concentration levels and duration and control had no significant (P > 0.05) effect on days to emergence (DE), seedling wet weight (WW), dry weight (DW), chlorophyll, stem diameter, plant height and final root length (RL). Furthermore, seeds primed at lower concentration levels (0.05, 0.01 and 0.1%) with longer duration priming period (24 hours) for Mo, Zn and B recorded higher results on the seedling emergence and establishment parameters. The field investigation showed that priming with micronutrients solutions had no significant difference on the final values of dry biomass, prolificacy, harvest index and grain yield. Seeds primed with 0.05, 0.01 and 0.1 % concentration levels with longer duration priming period (24 hours) showed improvement in germination and seedling establishment. The grain yield and grain nutrient content was not improved, meanwhile emergence was improved. This confirms that not only micronutrients limit yields maximization and crop nutrients content retention solely, rather that the complexity of the agricultural crop production environment should be well understood by all farmers to archive their goals. Keywords: Boron, Maize, Micronutrients, Molybdenum, Nutrient seed priming, Zinc. / National Research Foundation (NRF)

The bulk of Zimbabwe’s groundnut (Arachis hypogaea L.) crop is grown on sandy soils in the smallholder sector where sustainable production is hindered by acid soil infertility. The study goal was thus to examine the effects of soil acidity amelioration by four Ca-containing materials on nutrient composition, vegetative and reproductive growth, and quality of groundnut to formulate ameliorative strategies to improve productivity on acid soils. The effectiveness of calcitic lime (CL), dolomitic lime (DL), gypsum (G) and single superphosphate (SSP) in ameliorating soil acidity was determined in field experiments conducted for three seasons at two Research Stations in Zimbabwe, and in greenhouse experiments conducted for two seasons at Harare Research Station. In both experiments the lime application rates were from 0 to 4000 kg ha-1, while G application rates were from 0 to 3450 kg ha-1, and those of SSP were from 0 to 250 kg ha-1. Calcitic or dolomitic lime applied at 2000 or 4000 kg ha-1 increased soil pH and Ca and Mg contents in the pod and root zones, and in the plant material. Gypsum and SSP applications at 200 and 250 kg ha-1 respectively, had no significant effects on pH, Ca and Mg levels, but when applied in equivalent amounts of Ca as lime, gypsum improved soil Ca status. Effects of the four ameliorants on the N, P and K levels in the soils and in plant material were generally neither significant nor consistent. The direct and residual benefits of application of CL or DL were manifested in improved plant stands, better growth, nodulation, productivity and quality of groundnut. Gypsum applied at equal Ca rates as CL or DL was the superior Ca-source in improving pod and kernel quality. By the end of the third season, the increases in cumulative kernel yields due to application of 4000 kg ha-1 lime over non-application were up to 319%. The major growth-limiting factors on the studied acid soils were identified as deficiencies of Ca and Mg, and low pH per se. In a field experiment conducted to evaluate the tolerance of 15 groundnut genotypes to soil acidity, significant differences in yield and nutrient utilization efficiency of the genotypes were observed, implying that productivity on acid soils can be increased by growing genotypes efficient in uptake and utilization of nutrients. Results from greenhouse and growth chamber studies conducted to examine the effects of pH (3.0 - 7.0) and its interactions with Ca (0 - 2000 µM Ca) on early seedling growth and reproductive growth of groundnut indicated that low pH per se has a major detrimental impact on seedling survival, growth, pod formation, yield and quality of groundnut, but not on germination. The adverse effects of low pH were more pronounced in the absence of Ca, and became progressively less as the solution Ca concentrations increased. Further experiments showed that it is feasible to mitigate the adverse effects of soil acidity on groundnut germination and seedling survival by pelleting seeds with small amounts of CaCO3, or priming with CaSO4. / Dissertation (PhD (Plant Production: Agronomy))--University of Pretoria, 2003. / Plant Production and Soil Science / unrestricted

Salinity continues to be one of the world’s most serious environmental problems in agriculture. The increasing world population and urbanization are forcing farmers to utilize marginal lands as well as poor quality water. One of the strategies in dealing with salinity is growing salt tolerant plants and there has been increased need to understand the effects of salinity on crops. Owing to its high nutritive value and wide adaptability to diverse environments, amaranth is considered a promising crop for marginal lands and semiarid regions. The objective of the study was to investigate the response of amaranth to salinity stress and evaluate stress amelioration by calcium and seed priming. Salinity tolerance during germination and early seedling growth was examined for six genotypes of amaranth (Amaranthus species) at different salt concentrations ranging from 0 to 200 mM NaCl or Na2SO4. Enhancement of germination was observed at 25 mM, while increasing salt concentrations reduced the germination percentage as well as germination rate. A.tricolor and Accession ’83 were able to germinate in 200 mM NaCl while there was no germination at 200 mM Na2SO4 in all the genotypes. Overall, Accession ’83 was the most resistant and A. hybridus the most sensitive genotype, particularly at high salt concentrations. Inhibition of germination was greater in Na2SO4 than in NaCl salinity treatments. Amaranth was more salt tolerant at germination than at seedling growth. Seedling emergence, survival and growth were reduced by salinity and at much lower concentrations than at seed germination. Differences in salt tolerance were noted among the genotypes. Salinity stress was initiated at different growth stages (cotyledon stage, 2-leaf stage and 4-leaf stage) in order to determine whether tolerance of amaranth differs with the stage of development. The treatment either continued until termination of the experiment or for 14 days at each stage. Amaranth plants were less sensitive to salinity when the stress was initiated at the 4-leaf stage. Lower salt concentrations had less detrimental effects than higher concentrations when applied at the cotyledon stage. Application of low salt concentration at cotyledon stage for 14 days did not have any effect on plant growth. The results indicate that it is feasible to use saline water for growing amaranth with minimum yield losses if salt concentration, duration of exposure and time of salinization are carefully managed. Differences in salinity tolerance among amaranth genotypes were analyzed in terms of plant survival, growth, gas exchange, water use and leaf anatomical changes. A. hypochondriacus and A. cruentus showed greater tolerance to salinity since they survived in 200 mM NaCl treatment and the reduction in growth at 50 and 100 mM was lower than that of A. tricolor and Accession ’83. A. hypochondriacus and A. cruentus were more efficient water users and partitioned photosynthates towards shoot growth as opposed to the other two genotypes. Photosynthetic rate, stomatal conductance, stomatal density and apertures were reduced by salinity but were higher in A. tricolor than in A. cruentus. Salinity resulted in A. cruentus developing thicker leaves compared to A. tricolor. Productivity on saline soils can be increased by growing genotypes more tolerant to salinity. The interactive effect of salinity and water stress on amaranth plant growth was evaluated. It was found that the reduction in shoot growth was greater in plants submitted to water stress than in those submitted to salt or salt + water stress. Water use efficiency was increased while leaf water and osmotic potentials were reduced by the salinity stress treatments. In drying soil plants previously salinized had a greater degree of osmotic adjustment, so that plants were able to continue growth for a longer period compared to water stressed plants. The effect of calcium in ameliorating salt stress was investigated. Supplementary calcium, either as CaSO4 or CaCl2 ameliorated the negative effects of salinity on growth, gas exchange, membrane permeability and mineral uptake. In a separate experiment it was shown that it is feasible to mitigate the adverse effects of salinity on amaranth seed germination, seedling survival and growth by seed priming and that the positive effect of priming persisted to vegetative growth stage. Priming with CaSO4 + NaCl showed a greater positive response than priming with the individual salts. / Thesis (PhD (Plant Production andSoil Science))--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted