Aplicação de ferro e intensidade de radiação solar modula o metabolismo em plantas de Mentha piperita L.
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Data
2021-02-10
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Universidade Estadual Paulista (Unesp)
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A hortelã-pimenta (Mentha piperita L.) é uma planta medicinal com potencial na medicina tradicional, indústria farmacêutica e de perfumes. Os compostos ativos das plantas resultam tanto do metabolismo primário como do secundário, mais recentemente denominado especializado. Condições ambientais, como intensidade da radiação solar e a nutrição mineral modulam o metabolismo vegetal influenciando a fisiologia, bioquímica e anatomia desses indivíduos. O presente estudo tem como objetivo analisar respostas fisiológicas, bioquímicas e anatômicas em plantas de M. piperita submetidas à aplicação de ferro (Fe) e diferentes intensidades de radiação solar. O experimento foi conduzido em casa de vegetação, com controle de umidade e temperatura. O delineamento experimental foi inteiramente casualizado em esquema fatorial com 2 fatores: concentrações de Fe (5 concentrações) e 2 condições de irradiância I100% (pleno sol) e I50% (irradiância 50%). As concentrações de Fe aplicados via foliar foram: 0 (controle), 0,5, 1,0, 1,5 e 2,0 g L-1 e duas condições de irradiância, I100% e I50%. Foram realizadas avaliações de crescimento, teores de pigmentos, Fe foliar e, carboidratos, bem como trocas gasosas, fluorescência da clorofila a, respostas relacionadas ao sistema antioxidante e modificações anatômicas. No capítulo 1, os resultados revelam que em curto período de tempo, a maior sensibilidade as maiores concentrações de Fe são causadas pelo comprometimento da fotossíntese, como a concentração interna de CO2 (Ci) e eficiência de uso de água, desencadeada por dano oxidativo e sua consequente incapacidade de extinguir o excesso de energia entre os fotossistemas, como revelado pela elevação de coeficiente de extinção fotoquímica (qP) e diminuição de quenching não fotoquímico (NPQ). A condição de I50% eleva os valores de clorofilas (a e b), carotenoides, Ci, transpiração, fluorescência mínima da folha adaptada ao claro (F0'), fluorescência máxima da folha adaptada ao escuro (Fm) e ao claro (Fm’), eficiência quântica da antena (Fv’/Fm’), fluorescência variável adaptada ao claro (Fv’) e ao escuro (Fv). A condição em pleno sol (I100%) aumenta a fluorescência mínima da folha adaptada ao escuro (F0) e a taxa de transporte de elétrons. Nos capítulos 2 e 3, os resultados revelam que o crescimento, concentração de clorofilas, assimilação e uso de CO2 são influenciados positivamente pela aplicação com concentrações menores de Fe, refletindo em maior produção de biomassa total. De maneira em geral, a aplicação de Fe não prejudica o aparato fotossintético, sem alteração na produção de peroxido de hidrogênio, apesar de modificar discretamente peroxidação lipídica, no entanto, incrementa respostas do sistema antioxidantes. A condição I100% reflete positivamente em incrementos de trocas gasosas, biomassa e compostos fenólicos totais. No capítulo 4, o teor de Fe foliar é proporcional a concentração aplicada desse elemento e com maior acúmulo em condição de menor incidência solar (I50%). Plantas pulverizadas com 1,5 g L-1 de Fe em condição de I50% aumenta a espessura do mesofilo foliar. A área ocupada pelos espaços intercelulares do mesofilo foi afetada significativamente na presença de 1,5 g L-1 de Fe sob redução do nível de irradiância (I50%). A aplicação de Fe reduz o número de elementos condutores na nervura principal. De maneira em geral, o ambiente com sombreamento (I50%) diminui espessuras da epiderme da face adaxial e dos parênquimas paliçádico e esponjoso. Em busca de maior produtividade de plantas de M. piperita, recomenda-se concentrações menores de Fe e cultivo em condição de maior intensidade de radiação solar.
Peppermint (Mentha piperita L.) has medicinal properties and is largely employed in both pharmaceutical and cosmetic industries. The plants’ active compounds come from both primary and secondary metabolism, which is recently called specialized. Then, environmental conditions, such as solar radiation intensity and mineral nutrition modulate plant metabolism; consequently, influencing their physiology, biochemistry, and morphology. The present study aimed to analyse physiological, biochemical, and morphological responses in M. piperita plants subjected to iron (Fe) application under different solar radiation conditions. The experiment was conducted in a greenhouse with controlled humidity and temperature. The experimental design was completely randomized in a 5x2 factorial scheme, that is, five Fe concentrations (0 [control], 0.5, 1.0, 1.5 and 2.0 g L-1) and two irradiance conditions (I100% [full sunlight] and I50% [50% irradiance]. The following parameters were analysed growth evaluations, pigments levels, Fe in leaf and carbohydrates, besides gas exchange, chlorophyll a fluorescence, responses related to the antioxidant system and morphological changes. In the first chapter, the results showed the greater sensitivity to higher Fe concentrations are caused by photosynthesis impairment in a short period of time, such as the internal CO2 concentration of (Ci) and water use efficiency, triggered by oxidative damage and, consequently, the inability to extinguish excess energy between photosystems, since there was an increase in the photochemical extinction coefficient (qP) and a decrease in non-photochemical quenching (NPQ). The I50% condition increases the values of chlorophylls (a and b), carotenoids, Ci, transpiration, minimum fluorescence in light adapted leaf (Fo'), maximum fluorescence in the dark adapted leaf (Fm) and light adapted leaf (Fm'), antenna quantum efficiency (Fv'/Fm'), variable fluorescence adapted to light (Fv') and dark (Fv). The full sunlight condition increases the minimum fluorescence in dark adapted leaf (Fo) and electron transport rate. In the second and third chapters, results showed that growth, chlorophyll concentration, CO2 assimilation and uptake are positively influenced by lower doses of Fe; thus, a higher total biomass production. In general, Fe application does not harm the photosynthetic apparatus without altering hydrogen peroxide production, despite the slight change in lipid peroxidation; however, it increases responses to antioxidant system. The I100% reflects positively in gas exchange, biomass, and total phenolic compounds. In the fourth chapter, the Fe content in leaf is proportional to the applied concentration of this element, besides the greatest accumulation under lower irradiance conditions (I50%). Plants sprayed with 1.5 g L-1 of Fe and I50% increased the thickness of the leaf mesophyll. The area occupied by the intercellular spaces of the leaf mesophyll was significantly affected with 1.5 g L-1 of Fe under low irradiance condition (I50%). The Fe application reduces the number of conductive elements in leaf midrib. In general, shaded environment (I50%) decreases the thickness of the epidermis of the adaxial face and the palisade and spongy parenchyma. In a search for high yield of M. piperita plants, low Fe concentrations and cultivation area under full sunlight are recommended.
Peppermint (Mentha piperita L.) has medicinal properties and is largely employed in both pharmaceutical and cosmetic industries. The plants’ active compounds come from both primary and secondary metabolism, which is recently called specialized. Then, environmental conditions, such as solar radiation intensity and mineral nutrition modulate plant metabolism; consequently, influencing their physiology, biochemistry, and morphology. The present study aimed to analyse physiological, biochemical, and morphological responses in M. piperita plants subjected to iron (Fe) application under different solar radiation conditions. The experiment was conducted in a greenhouse with controlled humidity and temperature. The experimental design was completely randomized in a 5x2 factorial scheme, that is, five Fe concentrations (0 [control], 0.5, 1.0, 1.5 and 2.0 g L-1) and two irradiance conditions (I100% [full sunlight] and I50% [50% irradiance]. The following parameters were analysed growth evaluations, pigments levels, Fe in leaf and carbohydrates, besides gas exchange, chlorophyll a fluorescence, responses related to the antioxidant system and morphological changes. In the first chapter, the results showed the greater sensitivity to higher Fe concentrations are caused by photosynthesis impairment in a short period of time, such as the internal CO2 concentration of (Ci) and water use efficiency, triggered by oxidative damage and, consequently, the inability to extinguish excess energy between photosystems, since there was an increase in the photochemical extinction coefficient (qP) and a decrease in non-photochemical quenching (NPQ). The I50% condition increases the values of chlorophylls (a and b), carotenoids, Ci, transpiration, minimum fluorescence in light adapted leaf (Fo'), maximum fluorescence in the dark adapted leaf (Fm) and light adapted leaf (Fm'), antenna quantum efficiency (Fv'/Fm'), variable fluorescence adapted to light (Fv') and dark (Fv). The full sunlight condition increases the minimum fluorescence in dark adapted leaf (Fo) and electron transport rate. In the second and third chapters, results showed that growth, chlorophyll concentration, CO2 assimilation and uptake are positively influenced by lower doses of Fe; thus, a higher total biomass production. In general, Fe application does not harm the photosynthetic apparatus without altering hydrogen peroxide production, despite the slight change in lipid peroxidation; however, it increases responses to antioxidant system. The I100% reflects positively in gas exchange, biomass, and total phenolic compounds. In the fourth chapter, the Fe content in leaf is proportional to the applied concentration of this element, besides the greatest accumulation under lower irradiance conditions (I50%). Plants sprayed with 1.5 g L-1 of Fe and I50% increased the thickness of the leaf mesophyll. The area occupied by the intercellular spaces of the leaf mesophyll was significantly affected with 1.5 g L-1 of Fe under low irradiance condition (I50%). The Fe application reduces the number of conductive elements in leaf midrib. In general, shaded environment (I50%) decreases the thickness of the epidermis of the adaxial face and the palisade and spongy parenchyma. In a search for high yield of M. piperita plants, low Fe concentrations and cultivation area under full sunlight are recommended.
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Palavras-chave
Planta medicinal, Micronutriente, Irradiância, Metabolismo vegetal, Estrutura foliar, Medicinal plant, Micronutrient, Irradiance, Plant metabolism, Leaf structure