Effect of Water Deficit Stress on Growth, Yield, Essential Oil Content and Composition of Pelargonium graveolens L.

In order to study the effect of water deficit stress on growth، yield، essential oil content and composition of geranium (Pelargonium graveolens L.)، a greenhouse experiment was carried out based on a completely randomized design with four treatments and four replications. The water deficit stress treatments were 100%، 85%، 70% and 55% of field capacity. Results showed that as the soil water content decreased، plant height، stem diameter، number of auxiliary shoots، fresh and dry herb yield and essential oil yield decreased. Although the highest essential oil content (2. 04% based on dry weight) was found in plants treated with 55% of filed capacity، due to dramatic decrease in growth، their oil yield (0. 065 g plant-1) was the lowest compared with those of plants treated with 100%، 85%، 70% of field capacity. The highest oil yield with 0. 193 g plant-1were found in plants treated with 100% of field capacity. The amount of some of the main components of oil i. e. Citronellol، Citronellyl formate and iso-Menthone were not affected by water deficit stress treatments. However، as the soil water content decreased، the amount of α-Pinene and Linalool decreased، while the amount of 2-Phenylethyl tiglate and Germacrene-D increased. Moreover، the highest amount of Rose oxide (cis and trans)، Spathulenol، cis-Citronellyl tiglate and the lowest amount of Neral، Geraniol and Geranyl formate were found in plants treated with 55% of field capacity، while those of plants treated with 100%، 85%، 70% of field capacity were not significantly different. Due to the effect of water stress on herb yield، the yield (mg plant-1) of the main components decreased as the soil water content decreased.