Abstract:
Isabgol (Plantago ovata Forsk), is an annual herb cultivated as a medicinal plant in
recent decades. Its seed contains mucilage, fatty oil, large quantities of albuminous
matter, a pharmacologically inactive glucoside, namely Aucubin (C13 H19 O8 H2O), and a
plantiose sugar. Medicinal plants are rich in secondary metabolites: their biosynthesis is
controlled genetically and is affected strongly by environmental factors. In the present
work, the influence of sowing dates (20th April, 5th and 20th May) and nitrogen-fertilizer
levels (0, 50, 100 and 150 kg ha-1) was examined on the growth, seed yield and seed
swelling factor (content of mucilages) of isabgol. The statistical design was a split-plot
arrangement of a randomized complete block design with three replicates: the sowing
dates and nitrogen fertilizer were considered as the main and sub-main plots,
respectively. The plot experiment was installed in the experimental station of Zanjan
region located in the northwest of Iran, under silty-clay soil conditions. According to the
resulting data, the best time for sowing isabgol in such a region was 5th May and the
suitable amount of nitrogen fertilizer was 100 kg ha-1. To discover any relationship, all
measured independent variables were muliple regressed on the dependent variable (seed
yield) followed by stepwise regression analysis. This verified that the seed yield among
other independent characteristics tested appeared to show a significant positive effect on
the seed swelling
