Aspects of seeds germination and influence of light on the development, leaf anatomy and chemical composition of essential oil in Ocimum gratissimum L. / Aspectos da germinaÃÃo das sementes e influÃncia da luz no desenvolvimento, anatomia foliar e composiÃÃo quÃmica do Ãleo essencial em Ocimum gratissimum L.

AUTOR(ES)
DATA DE PUBLICAÇÃO

2006

RESUMO

Before the need to deepen the knowledge about medicinal flora, the species Ocimum gratissimum L., an important producer of essential oil much utilized as a phytotherapeutic, was selected. The main objectives in this work were to evaluate physiologic aspects of germination and storage of seeds as well as to investigate growth leaf anatomy and accumulation of essential oils of young plants of this species when submitted to different light conditions (under full sunshine, under black and blue meshes of 50% of shading). The seeds of this species showed an equivalence in the reserve classes, there being the predominance of proteins. The X ray test was an effective and non-destructive method in a complementary evaluation of quality of the seeds, since it enabled the sharp viewing of full and empty seeds, its being able to be useful in the complementation of germination tests. The seeds stored for twelve months both in the laboratory bench setting (climatic conditions of Lavras, MG) and in refrigerator (10ÂC and 50%) or cold chamber (10ÂC and 45% RH, utilizing the packages paper bag alminized paper bag or glass flask did not loss physiological quality. The best results of germinability, germination velocity, average time and normal seedlings took place in the presence of light, at the alternate temperature of 20-30ÂC and at constant temperature of 30ÂC, but, germinability did not exceed 55%. The seeds of O. gratissimum L. can be regarded as preferential positive photoblastic, since they alternate temperatures (15-25ÂC and 20-30ÂC), in the absence of light, a distinct germination occurs in the presence of light, the concentrations of GA3 did not change germinability, but in the absence of light and under alternate temperature of 20-30ÂC, GA3 acted in an effective way promoting the best values of germinability, IVG and average time. The plants of Ocimum gratissimum L. show a physiological and anatomical plasticity for the different treatments relating to radiation. The plants grown under full sunshine had the highest accumulation of dry matter, the smallest leaf area, the greatest leaf thickness, the highest caratenoid content and the greatest thickness of stomas, tector and glandular trichomes on the adaxial surface of leaves. The radiation transmitted by the blue mesh provided the greatest height growth, largest leaf area and stomatal functionality. The plants of O. gratissimum L. grown under conditions of partial shading accumulated greater amount of essential oil than those in the full sunshine. The spectral quality of radiation in the environment under the blue mesh allowed to the species O. gratissimum L. to yield 142% more of essential oil per unit of dry matter. The quantitative analysis of the essential oil enable to classify the plants of Ocimum gratissimum L. utilized in this experiment as belonging to the chemiotype eugenol, for this is the most widespread compound, representing from 83 to 88% of the essential oil among the treatments.

ASSUNTO(S)

seeds Ãleo essencial alfavaca sweet basil sementes essential oil fisiologia de plantas forrageiras storage armazenamento

ACESSO AO ARTIGO

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