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O uso de extratos comerciais de macroalgas como bioestimulantes
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Abstract(s)
As algas, do termo em latim “planta marinha”, conhecidas como macroalgas e microalgas, têm despertado nos últimos anos, um elevado interesse. Encontradas em água doce, salobra ou salgada, estes organismos contêm vitaminas, minerais, proteínas, entre outros compostos de interesse, com bioatividades importantes como antibacteriana, antifúngica ou bioestimulante, entre outras. Rhodophyta, Chlorophyta e Phaeophyceae são os 3 grandes grupos de macroalgas que se distinguem pelos seus pigmentos. Um dos interesses das macroalgas, relaciona-se com uso das mesmas enquanto bioestimulantes, efeito muitas vezes correlacionado com a presença de fito-hormonas vegetais na sua composição. As auxinas e citocininas são as mais vulgarmente conhecidas, no entanto, tantas outras têm a sua função e importância. Estas fito-hormonas são extraídas através de extratos aquosos, uma vez que são solúveis em água, sendo os extratos de elevado rendimento e eficiência, economicamente acessíveis e de fácil repetição. Extratos algais encontram-se em comercialização, como seja o AcadianTM Soluble Seaweed Extract Powder (SSEP), produzido pela empresa HortFertplus a partir da macroalga castanha Ascophyllum nodosum, ou o AgroGain, produzido pela empresa Sea6Energy, na Índia, com base na macroalga vermelha Kappaphycus alvarezii. A macroalga A. nodosum é comummente usada como bioestimulante, devido à presença de fito-hormonas como citocininas, ácido abcísico e giberelinas. Já a K. alvarezii possui maioritariamente auxinas, citocininas e giberelinas. As fito-hormonas, comprovadamente, aceleram a germinação das sementes, e ainda, aumentam a resistências das plantas a fatores de stress (particularmente o ácido abcísico). Outros componentes, como enzimas, naturalmente presentes, podem ter um impacto conjunto com as fito-hormonas. Assim, este trabalho visou testar a eficácia de dois extratos comerciais enquanto bioestimulantes em alface, Lactuca sativa, e tomate, Solanum lycopersicum. Foram realizados testes de germinação, de crescimento e testes de stress. Concluiu-se que os extrato algais em concentrações muito elevadas têm efeito inibitório. Para a germinação, a concentração mais adequada para alface e para tomate foi de 2%. Verificou-se também que diferentes metodologias têm impacto nos resultados dos ensaios desenvolvidos. Assim, sementes previamente embebidas no extrato têm melhores resultados relativamente à utilização do extrato incorporado no meio de cultivo, sendo que em tomate, registou-se maior taxa de germinação nas sementes embebidas e melhor estado fisiológico e sanitário. Finalmente, nos ensaios de stress salino apenas se obtiveram resultados positivos para
uma concentração de 5‰. Os extratos utilizados demostraram melhorar as taxas de germinações apenas em sementes de alface. Futuramente, o aumento do número de amostras e de testes com intervalos mais específicos, como o intervalo 5‰ - 15 ‰, são a considerar. Já a temperatura de germinação de 35°C foi muito prejudicial para o tomate, não se tendo obtido qualquer germinação, enquanto para a alface, esta rondou apenas os 60%.
A analise química elementar das plantas testadas, seriam novos elementos a considerar para obtenção de resultados mais completos.
Algae, from the Latin term "sea plant", known as macroalgae and microalgae, have aroused high interest in recent years. Found in fresh, brackish, or salt water, these organisms contain vitamins, minerals, and proteins, among other compounds of interest, with important bioactivities such as antibacterial, antifungal, or biostimulant, among others. Rhodophyta, Chlorophyta and Phaeophyceae are the 3 major groups of macroalgae that are distinguished by their pigments. One of the interests in macroalgae is related to their use as biostimulants, an effect often correlated with the presence of plant phytohormones in their composition. Auxins and cytokinins are the most known, however, many others have their function and importance. These phytohormones are extracted through aqueous extracts, since they are water soluble, and the extracts are high yielding, efficient, economically accessible, and easily repeatable. Algae extracts are commercially available, such as the AcadianTM Soluble Seaweed Extract Powder (SSEP), produced by HortFertplus from the brown macroalgae Ascophyllum nodosum, or AgroGain, produced by Sea6Energy in India, based on the red macroalgae Kappaphycus alvarezii. The macroalga A. nodosum is commonly used as a biostimulant, due to the presence of phytohormones such as cytokinins, abscisic acid, and gibberellins. K. alvarezii has mainly auxins, cytokinins, and gibberellins. The phytohormones have been shown to accelerate seed germination, and to increase the plants' resistance to stress factors (particularly abscisic acid). Other naturally occurring components or enzymes may have a joint impact with phytohormones. Thus, this work aimed to test the effectiveness of the two commercial extracts as biostimulants on lettuce, Lactuca sativa, and tomato, Lycorpersicum esculentum. Germination tests, growth tests, and stress tests were performed. It was concluded that algal extracts at very high concentrations have an inhibitory effect. For germination, the most suitable concentration for lettuce and for tomato was 2%. It was also found that different methodologies have an impact on the results of the tests developed. Thus, seeds previously soaked in the extract have better results when compared to the use of the extract incorporated in the growing medium, and in tomato, there was a higher germination rate in soaked seeds and better physiological and health status. Finally, in the stress tests, salinity was found to be positive only at a concentration of 5‰. The extracts used were shown to improve germination rates, only for lettuce seeds. In the future, increasing the number of samples, tests with more specific ranges, such as the range 5‰ - 15 ‰, are to be considered. The germination temperature of 35°C, on the other hand, was very detrimental for tomatoes, obtaining no germination, while for lettuce, it was only around 60%. The elemental chemical analysis of the tested plants would be new elements to consider in order to obtain more complete results.
Algae, from the Latin term "sea plant", known as macroalgae and microalgae, have aroused high interest in recent years. Found in fresh, brackish, or salt water, these organisms contain vitamins, minerals, and proteins, among other compounds of interest, with important bioactivities such as antibacterial, antifungal, or biostimulant, among others. Rhodophyta, Chlorophyta and Phaeophyceae are the 3 major groups of macroalgae that are distinguished by their pigments. One of the interests in macroalgae is related to their use as biostimulants, an effect often correlated with the presence of plant phytohormones in their composition. Auxins and cytokinins are the most known, however, many others have their function and importance. These phytohormones are extracted through aqueous extracts, since they are water soluble, and the extracts are high yielding, efficient, economically accessible, and easily repeatable. Algae extracts are commercially available, such as the AcadianTM Soluble Seaweed Extract Powder (SSEP), produced by HortFertplus from the brown macroalgae Ascophyllum nodosum, or AgroGain, produced by Sea6Energy in India, based on the red macroalgae Kappaphycus alvarezii. The macroalga A. nodosum is commonly used as a biostimulant, due to the presence of phytohormones such as cytokinins, abscisic acid, and gibberellins. K. alvarezii has mainly auxins, cytokinins, and gibberellins. The phytohormones have been shown to accelerate seed germination, and to increase the plants' resistance to stress factors (particularly abscisic acid). Other naturally occurring components or enzymes may have a joint impact with phytohormones. Thus, this work aimed to test the effectiveness of the two commercial extracts as biostimulants on lettuce, Lactuca sativa, and tomato, Lycorpersicum esculentum. Germination tests, growth tests, and stress tests were performed. It was concluded that algal extracts at very high concentrations have an inhibitory effect. For germination, the most suitable concentration for lettuce and for tomato was 2%. It was also found that different methodologies have an impact on the results of the tests developed. Thus, seeds previously soaked in the extract have better results when compared to the use of the extract incorporated in the growing medium, and in tomato, there was a higher germination rate in soaked seeds and better physiological and health status. Finally, in the stress tests, salinity was found to be positive only at a concentration of 5‰. The extracts used were shown to improve germination rates, only for lettuce seeds. In the future, increasing the number of samples, tests with more specific ranges, such as the range 5‰ - 15 ‰, are to be considered. The germination temperature of 35°C, on the other hand, was very detrimental for tomatoes, obtaining no germination, while for lettuce, it was only around 60%. The elemental chemical analysis of the tested plants would be new elements to consider in order to obtain more complete results.
Description
Keywords
Macroalgas Bioestimulante Extrato algal comercial Germinação Crescimento Alface Tomate