Caracterização fisiológica e produção de metabólitos secundários em Achillea millefolium L. após aplicação de quitosana

Elicitation with chitosan is a tool used to improve the responses of plant defense by inducing secondary metabolism routs. In addition, the adequate application of this elicitor on medicinal plants can promote the increase of major components in the composition of the oil. However, we lack information concerning which are the main physiological processes responsible for the changes in the composition of the oil. Thus, we aimed at evaluating the action of chitosan and determine an ideal concentration for optimizing the production of essential oil in Achillea millefolium L. and the changes in the physiological processes responsible for this increase. The research was conducted in greenhouse of the Plant Physiology sector of the Universidade Federal de Lavras (UFLA) with A. millefolium plants. The treatments consisted of control (water); acetic acid solvent (with no elicitor); and chitosan in the concentrations of 2, 4 and 6 g L -1 . The measurements of growth, gas exchange, enzyme activity of the antioxidant system and phenylalanine ammonia lyase (PAL), in addition to the production and composition of the essential oil. We verified that the application of chitosan promoted decrease in plant growth. However, the concentration of 4 g L -1 of chitosan induced an increase in the content and yield of the essential oil. In the oil, there was predominance of sesquiterpenic compounds, including the major compounds borneol, β-caryophyllene, β-cubebene, α-farnesene and chamazulene. The elicitation with chitosan at 4 g L -1 promoted an increase of the photosynthetic rate, activity of the antioxidant system and of PAL, however, this increase occurred in short-term, only in the first days after elicitation.

Influência do etileno na regulação do florescimento de Coffea arabica L.

Coffee is one of the most valuable exported agricultural product worldwide as well as the second most traded commodity after oil. This crop represents a source of employment and considerably accounts for the revenue of the country, besides its undeniable importance for local and world socioeconomical scenery. The quality of the coffee drink is directly related to the fruit ripening stage, which is found in different stages at harvesting due to the sequential flowering, increasing costs with the production and generating a lower-quality beverage. The asynchronous flowering of the coffee tree comes from the uneven development of buds, which can be influenced by environmental factors, taking into account that the anthesis takes place after a water deficit period, followed by precipitation. Changes in the hormone balance have been observed after water deficit and rehydration cycles, and such oscillation on the water status of the plant increased the level of ethylene in some species. This finding led to the association between the requirements at the flowering stage of the coffee tree and the involvement of the ethylene in promoting anthesis. The application of 1- MCP (ethylene action inhibitor) triggered the anthesis in coffee trees. And, in coffee seedlings in greenhouse conditions after a period of water shortage followed by irrigation, the profile of gene expression of the biosynthesis route and signaling of ethylene are changed in leaves and roots. The increased levels of the ethylene precursor (ACC) in roots throughout the dry season and the transportation of this compound into shoots may be the signal to trigger the anthesis in coffee tree after rehydration. Thus, in order to better understand the role of the ethylene in regulation of flowering, we analyzed the effects of the exogenous application of 1-MCP in different physiological characteristics and in the expression of genes related to the ethylene biosynthesis and signaling pathways in coffee leaves and bud from plants under field conditions. The evaluations and tissue sampling were carried out in different times treatments implementation: T1 – control, T2 – 1-MCP+Break-Thru, and T3 – Break-Thru. There was influence of 1-MCP and Break-Thru in gas exchange parameters and of 1-MCP contributed to the increase in relative water content. RT-qPCR analyses showed a different behavior in relation to the profile of gene expression in leaves and buds analyzed in the present study (CaACS1 – like, CaACO1 – like, CaACO4 – like, CaETR4 – like) and the expression levels were changed a few hours (2h) after applying the products. However, there was flowering only in plants treated with 1-MCP, in the absence of rain and irrigation.

Compartimentos de K, Ca e Mg em solos e sua relação com o crescimento inicial, fisiologia e produtividade do eucalipto

Forestry has grown in a continuous and accelerated manner in Brazil, constituting a strategic activity for the generation of employment, income and tributes, favoring social and economic development of Brazilian agribusiness. The objectives of this study were: (1) evaluate the contents of K, Ca and Mg in the reserve compartments, non-interchangeable, interchangeable, available and the speed of its release, its correlations and its effects over productivity (annual average increment – AAI) of eucalyptus plantations, in forest sites cultivated in soils of the state of Rio Grande do Sul; (2) evaluate the initial growth, nutrition and physiological aspects of eucalyptus plants, cultivated with and without the addition of mineral sources of potassium (K), calcium (Ca) and magnesium (MG), in soils obtained from forest sites in the state of Rio Grande do Sul. In the first study, contents of K, Ca and Mg were evaluated in sulfuric digestion extract, boiling nitric acid, ammonium chloride, Mehlich-1 (only K), potassium chloride (Ca and Mg), as well as the release speed of these nutrients in the soil. In the second study, growth variables, nutritional aspects, photosynthetic rate (A) and transpiration rate of the plants (E) grown in distinct soils were evaluated under controlled conditions. The contents of K, Ca and Mg varied between compartments and depths in the studied soil classes, with the highest proportions found in the reserve compartment, indicating the importance of this compartment for the supplement of these nutrients at average and long terms. The great majority of K, Ca and Mg compartments presented significant correlations between each other, showing the dependence between them and the importance of evaluating the contents of these nutrients in the different compartments to adapt the nutritional management of the plants to each soil class, and to obtain continuous productions, minimizing the negative effects to the environment. Plants cultivated in soils that present larger reserves, availability and K, Ca and Mg release kinetics, presented similar height (H), stem diameter (SD) and shoot dry mass (SDM), with or without fertilization with K, Ca and Mg. The plants presented higher leaf content and accumulation of K in all soils fertilized with K, Ca and Mg.

Processo infeccioso de Pseudocercospora musae e severidade da Sigatoka Amarela da bananeira em função do silício, potássio e cálcio em solução nutritiva

Yellow Sigatoka leaf spot, caused by Pseudocercospora musae (Mycosphaerella musicola), is one of main threats to banana production around the world. However, information regarding the infection process of P. musae and the influence of mineral nutrition on the disease severity could help with cultural control strategies and increase the fruit yield. Therefore, this work aimed to characterize the infectious process of P. musae in banana leaves, to study the effect of silicon (Si) and the interaction between potassium (K) and calcium (Ca) on the Yellow Sigatoka leaf spot severity. In the first study, samples were inoculated on the abaxial leaf surface with P. musae and analyzed at 12, 24, 36, 48, 72, 96, 120, 144, and 168 hours after inoculation (HAI) as well as 36 and 50 days after inoculation (DAI). The conidia germinated between 24 and 36 HAI and penetrated through the stomata between 96 and 120 HAI, or usually from 144 HAI. P. musae colonized intercellularly the spongy parenchyma at 36 DAI and inter- and intracellularly the palisade parenchyma at 50 DAI. The sporulation occurred at 50 DAI on the adaxial leaf surfaces. In the second study, banana plants grown in nutrient solution with 0; 0.5; 1.0; 1.8 and 3.6 mmol L -1 of silicic acid (H 4SiO 4) were inoculated with conidial suspension. The disease severity was assessed and data were integrated in the area under the disease severity progress curve (AUDSPC). The lower AUDSPC was 49.27% for the concentration of 3.05 mmol L -1 of H 4SiO 4 compared to plants grown without Si addition. Regarding silicon accumulation, at 3.6 mmol L -1 H4SiO 4, leaf Si content was 23.53% higher compared to the control. In the third study, plants grown in nutrient solution with 5 K concentrations (1, 2, 4, 6, and, 8 mmol L -1 ) combined with 5 Ca concentrations (1, 3, 5, 7, and, 9 mmol L -1 ), forming 25 treatments, were inoculated with conidial suspension. The disease severity was assessed and the data were integrated in the AUDSPC. There was no interaction between concentrations of K and Ca for AUDSPC, although the AUDSPC increased with the increase of K concentrations from 1 to 6 mmol L -1 . The K increase led to a reduction in chlorophyll a and b contents and in the N, P, Mg, B, Cu, Zn, and, Mn nutrients as well as increased the total plant dry weight.