Ali Saebi - Department of Biosystems Engineering, Faculty of Agriculture, Tarbiat Modares University (TMU), Tehran, Iran
Saeid Minaei - Department of Biosystems Engineering, Faculty of Agriculture, Tarbiat Modares University (TMU), Tehran, Iran
Ali Reza Mahdavian - Department of Biosystems Engineering, Faculty of Agriculture, Tarbiat Modares University (TMU), Tehran, Iran
Mohammad-Taghi Ebadi - Department of Horticultural Science, Faculty of Agriculture, Tarbiat Modares University, Tehran, Iran

The amount of active compounds of medicinal plants (e.g. essential oil) varies in different plant parts. Thus, it is important to harvest those parts containing the highest levels of active compounds. In the present study the effect of harvest height on quantity and quality of Hyssopus officinalis was investigated based on a randomized complete block design with three replications. Treatments included four harvest heights including 15, 25, 35, and 45 cm (in basipetal order) and the residual stalks. After measuring the essential oil, the component values analyzed by GC and GC/MS. Regarding essential oil content (% v/w), yield and dry matter of different heights, the 15 cm height had the highest amount of essential oil (1.02±0.01%) and the lowest yield (2.17±0.13 g/m2) and dry matter (213.72±15.32 g/m2). On the contrary, the 45 cm height had the lowest amount of essential oil (0.75±0.01%) and the highest yield (5.7±0.57 g/m2) and dry matter (757.52±63.5 g/m2). For all harvest heights, cis-pinocamphone (53.93-44.6%), β-pinene (15.33-12.5%) and trans-pinocamphone (12.2-8.17%) had the highest levels among the compounds of the essential oil. The findings obtained from present study revealed that, if the quality is the matter, the essential oil extracted from the top 15 cm had the highest quality and purity although it was less in quantity.

Precision harvesting, Harvest height, Medicinal plant, Essential oil, Cis-pinocamphone