Growth, photosynthetic pigments and production of essential oil of long-pepper under different light conditions

ABSTRACT Piper hispidinervum C. DC. is popularly known as long-pepper and it owns a commercial value due to the essential oil it produces. Long-pepper oil is rich in safrole and eugenoln components that have insecticidal, fungicidal and bactericidal activity. It has been establish that to medicinal plants light influences not only growth but also essential oil production. The growth, the content of photosynthetic pigments and the essential oil production of Piper hispidinervum at greenhouses with different light conditions was evaluated. The treatments were characterized by cultivation of plants for 180 days under different light conditions, produced by shading greenhouses with 50% and 30% of natural incident irradiance, two colored shading nets red (RN) and blue (BN) both blocking 50% of the incident radiation and one treatment at full-sun (0% of shade). The results showed that the treatments of 50% shade and RN and BN were the ones which stimulated the greater growth. Blue and red light also had the best production of photosynthetic pigments. Essential oil yielded more under full sun therefore this is the most indicated condition to produce seedlings for the chemical and pharmaceutical industry.

Anatomia foliar de plantas de alfavaca-cravo cultivadas sob malhas coloridas / Leaf anatomy of alfavaca-cravo plants cultivated under colored nets

No presente trabalho, foi avaliado o efeito do controle espectral da luz sobre características anatômicas de folhas em Ocimum gratissimum L. As plantas foram cultivadas por quatro meses sob malhas de 50 por cento de sombreamento nas cores preta, vermelha e azul e a pleno sol. Plantas submetidas a pleno sol apresentaram maior espessura foliar, maior densidade estomática e maior densidade de tricomas tectores e glandulares na face adaxial. As plantas cultivadas sob malhas coloridas não exibiram diferenças quanto à espessura e à área foliar. As plantas mantidas sob malha vermelha tiveram a menor densidade estomática na face adaxial, já as plantas mantidas sob malhas azul e vermelha exibiram maior área foliar total. As plantas mantidas sob malha vermelha apresentaram a menor densidade estomática e as menores densidades de tricomas tectores e glandulares na face adaxial. Tais resultados mostram que tanto a intensidade como a qualidade espectral da luz pode ser modulada durante o cultivo de Ocimum gratissimum L. a fim de serem obtidas características anatômicas desejáveis.

In the present research, the effect of spectral control of light was evaluated on anatomical characteristics of Ocimum gratissimum L. leaves. The plants were cultivated during four months under black, red and blue nets with 50 percent of shade, and full sunlight. Plants grown under full sunlight showed higher leaf thickness, higher stomatal density and higher density of no-glandular and glandular trichomes on the adaxial epidermis. Plants cultivated under colored nets did not show differences in leaf thickness or leaf area. Plants maintained under red net had the lowest stomatal density in adaxial epidermis, as the plants cultivated under blue and red nets exhibited the largest leaf area. The plants maintained under red net showed the smallest stomatal density and the smallest non-glandular and glandular trichomes density in the adaxial epidermis. Such results show that the spectral quality and intensity of light can be modulated during the cultivation of Ocimum gratissimum L. plants in order to obtain desirable anatomical characteristics.