Desempenho ecofisiológico e análise de compostos secundários de plantas de Piper aduncum sob efeito da radiação

Abstract

The medicinal plants are important secondary metabolites sources, and the concern in to optimize and to know the farming systems and the response to different environmental conditions is growing. The species known as long-pepper (Piper aduncum L.) has great potential for economic exploration because of the proven use of its essencial oil in the agriculture and in the human health, however, the secondary metabolites production may vary depending on several factors. Light, both in terms of quality and quantity, is a factor which stands out because it alters directly or indirectly these compounds synthesis. Thus, the aim of this work was to assess the growth, ecophysiological performance, leaf anatomy, secondary metabolites production, and Piper aduncum essencial oil components under different irradiance conditions. Piper aduncum seedlings were cultivated for 4 months under different irradiance levels, under sombrite (50%, 70% and 100%) and under red (RN) and blue (BN) shading nets. The experimental design used was completely randomized, and it was used twenty plants for growth evaluation, and five for anatomical and biochemical analysis. The growth in height, neck diameter, leaf area, leaf number, and greater investment in shoot was observed when plants were cultivated under red and blue nets. Though, the plants also exhibited adaptive growth traits under high irradiance conditions. The greatest amout of secondary compounds (total phenolic compounds, lignin, and flavonoids) were obtained in plants cultivated under blue net. However, the photosynthetic process and the pigment production were more efficient in intensity and light spectrum broader, showing photosynthetic traits more favorable when the plants were cultivated under 100% and 70% of irradiance. Regarding to leaf anatomy, it was observed alterations in the different irradiance conditions, showing leaf anatomy characteristics favorable to the development in high irradiance conditions, and under spectra enriched with blue light. The essencial oil composition differed between leaves and roots in this species, being observed only in the leaves the irradiance conditions effects. In the leaves were verified the predominance of sesquiterpenic nature compounds, with (E)-nerolidol (14,28-16,65) as the majority component, and linalol (9,33-13,44%); α-humuleno (8,45-10,62%); cis-cadin-4-en-7-ol (7,48-12,24%), and cariofileno (5,14-6,70%) as secondary components. All the leaves majority components had their level increased when plants were cultivated under 100% of irradiance, and under blue net. In the roots it was identified phenilpropanoic nature compounds predominance, with apiol (18,36-29,51%) as the majority component, and dillapiol (13,0-18,36%), β–selinene (14,11-16,47%), and butanoate -2- methyl- geranyl (8,92-13,6%) as secondary components. The majority of the root compounds exhibited increase in level in conditions with blue wave-length, excepting dillapiol whose production increased in 100% of irradiance. From the obtained data, it is possible to observe that Piper aduncum has great plasticity in relation to irradiance conditions, but exhibits greater growth and secondary compounds production when they were cultivated under high irradiance and in environments which receives greater irradiance quantities in the blue spectral region.