The present investigation was carried out during the two successive seasons
of 2002 and 2003 on marigold plant (Tagetes minuta, L.) at the Experimental Station
of Medicinal and Aromatic Plants, Fac. of Agric., Mansoura Univ. This work aimed to study the possibility of using spraying active dry yeast at
the concentrations of 0, 1, 2 and 3 gIL applied three times to improve growth and yield
parameters as well as the oil percentage and oil yield per plant. Also, to study the
effect of length of the storage period of the dried herbs on essential oil percentage
and its constituent. The results showed that although all the treatments improved the growth and
yield parameters, active dry yeast at the rate of 3 gIL proved to be the most favorable
as increases in both fresh and dry herb yields per plant, as well as the oil percentage
and oil yield per plant were achieved. Regarding storage period, the results also
showed that increasing the storage period of the dried herbs resulted in reduction of
the essential oil percentage. Gas Liquid Chromatography analysis of oil samples
revealed seven identified compounds. Storage period had a clear effect on the
chemical composition of the extracted marigold oil, since some of the principle
components increased such as limonen and cis-tagetone as the storage period
increased, while those of dihydrotagetone and ~-pinene decreased over the same
period compared with the control.