ABSTRACT
Clinopodium nepeta subsp. spruneri is an aromatic herb with a mint-oregano flavor, used in Mediterranean regions in traditional medicine. The aerial parts of the plant are rich in essential oil that has antioxidant, antimicrobial and anti-inflammatory properties as well as insecticidal activity. The aim of our work was to determine the yield and composition of the essential oil of the plant, in relation to the harvest season and cultivation method, i.e., outdoor, greenhouse and in vitro culture, using gas chromatography-mass spectrometry (GC-MS) as an analytical tool. Essential oil yield fluctuated similarly in outdoor and greenhouse plants during the year (0.9-2.6%), with higher percentages (2.1-2.6%) in the hottest periods June-October (flowering stage) and April (vegetative stage), and was similar to the yield in in vitro plants (1.7%). More compounds were identified in the oil of outdoor and greenhouse plants (35) compared to that of in vitro plants (21), while the main compounds were the same, i.e., pulegone (13.0-32.0%, highest in February-April, 15.0% in vitro), piperitenone oxide (3.8-31.8%, lowest in February, 34.2% in vitro), piperitone epoxide (4.6-16.4%, highest in February, 15.5% in vitro), D-limonene (2.1-8.8%, lowest in February, 10.0% in vitro), isomenthone (2.3-23.0%, highest in February, 4.6% in vitro), germacrene D (1.9-6.5% highest in December-April, 2.9% in vitro) and dicyclogermacrene (2.1-5.3%, highest in December-April, 5.2% in vitro). Therefore, greenhouse and in vitro cultures were equally efficient in yielding essential oil and its constituents as outdoor cultivation, while in outdoor and greenhouse cultivations, the harvest season, mainly due to the prevailing ambient temperatures, affected the essential oil yield and its percentage composition.
ABSTRACT
The aim of the study was to develop an efficient micropropagation protocol of Origanum scabrum, which will allow its commercial exploitation in the pharmaceutical and horticultural industries. First, the effect of the date of the explant collection (20 April, 20 May, 20 June, 20 July, 20 August) and the position of the explant on the plant stem (shoot apex, 1st node, 3rd node, 5th node) on the establishment of in vitro cultures was studied (1st experiment: Stage I). Next, the effect of temperature (15 °C, 25 °C) and the node position (microshoot apex, 1st node, 5th node) on the microplant production and ex vitro survival of plantlets was studied (2nd experiment: Stage II). The optimum season to collect explants from wild plants was shown to be during the vegetative growth of the plants (April to May), while the shoot apex and the 1st node were the most suitable explants. For the proliferation and production of rooted microplants, the best results were obtained from single-node explants excised from microshoots produced from 1st node-explants collected on 20th of May. Temperature did not affect microshoot number, leaf number and the percentage of rooted microplants, while microshoot length was higher at 25 °C. Moreover, microshoot length and the percentage of rooted microplants were higher in those derived from apex explants, while the survival of plantlets was not affected by treatments and ranged between 67% and 100%.
ABSTRACT
Origanum dictamnus L. (Lamiaceae) is a perennial herb endemic to the Greek island of Crete, widely used for tea preparation, medicinal purposes, and food flavoring, as well as an ornamental plant. The aim of this work was to introduce the species to the green roof sector while serving urban agriculture. Thus, its growth potential was investigated, along with the content of nutrients (N, P, K, Na) and the accumulation of heavy metals (Cu, Pb, Ni, Mn, Zn, Fe) in its tissues, in two cultivation sites in Athens, Greece, i.e., an extensive green roof and at ground level next to a moderate traffic road. Cultivation took place in plastic containers with a green roof infrastructure fitted, in two substrate types (grape marc compost, perlite, and pumice 3:3:4 v/v, and grape marc compost, perlite, pumice, and soil 3:3:2:2 v/v), with 10 cm depth. Plant growth was favored by the soil substrate, but it was also satisfactory in the soilless one. Cultivation site affected heavy metal accumulation, resulting in higher concentrations both in leaves and in flowers at street level, while no differences were observed in roots. Washing the tissues reduced heavy metal concentrations only in leaves produced at the street level. Substrate type significantly affected Mn concentration in all plant tissues and Fe in roots, with the highest values measured in the soil substrate. Thus, O. dictamnus could be effectively cultivated in sustainable green roofs, better on a soilless substrate to lower construction weight. Careful selection of the cultivation site could minimize contamination with environmental pollutants if human consumption is also desired.