Growing of the Cretan Therapeutic Herb Origanum Dictamnus in The Urban Fabric: The Effect of Substrate and Cultivation Site on Plant Growth and Potential Toxic Element Accumulation

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.

Chemometric evaluation of inorganic and organic parameters found in Rosaceae plants proposed as food supplements

“…the botanical garden) ensured that atmospheric deposition as well as influence of soil composition as influencing parameters for elemental uptake can be minimized. Even few meters in altitude might have a measurable impact on elemental content in leaves and flowers for herbs grown in urban area ( Martini et al, 2023 ). Comparison with other edible inflorescences (banana heart – Musa paradisiaca ) shows similar values for the macroelements Mg (1716 mg/kg) and Ca (2854 mg/kg), but unexpectedly neither Na nor K was present in detectable amounts ( Rosa et al, 2020 ).…”

Ameliorating Effects of Graphene Oxide on Cadmium Accumulation and Eco-Physiological Characteristics in a Greening Hyperaccumulator (Lonicera japonica Thunb.)

“…Different concentrations of Cd 2+ (0, 5 and 25 mg L −1 ) were obtained by CdCl 2 ·2.5H 2 O solution. According to the reported ranges of concentrations in previous studies [ 49 , 50 , 51 ], the experiment sets up four GO treatments, which contain 0, 10, 50 and 100 mg L −1 , respectively. The combined concentrations of GO and Cd (GO-Cd) were prepared by mixing GO and Cd alone, and twelve GO-Cd treatments were set up in the study as follows in Table 1 .…”

“…In urban environments, pollutants cannot exist in isolation. In addition to the potential impact of GO, excessive heavy metals derived from the metallurgy and mining industry, exhaust emission and sewage irrigation were released into the urban environment and pose a serious threat to the survival of human beings and greening plants [ 47 , 48 , 49 , 50 , 51 ]. Cadmium (Cd), as one of the most toxic heavy metals, has become a global issue of common concern due to its high persistency, strong water solubility and carcinogenicity [ 52 , 53 , 54 ].…”

A Polysaccharide-Based Integrated Nutrient Management System Enhances the Antioxidant Properties in Origanum dictamnus (Lamiaceae), a Valuable Local Endemic Plant of Crete

“…The developed protocol responds to the extant information gap regarding the fertilization requirements of O. dictamnus and was specifically designed to improve its yield, as well as critical quality aspects (i.e., color intensity, antioxidant element concentration). In addition, this investigation explored nutrients' accumulation and partitioning in different plant organs of O. dictamnus, for which only little is regrettably known [45]. Such knowledge would be essential to induce growth and biomass yield potential of O. dictamnus by regulating nutrients supply according to species-specific needs, further elucidating how the latter correlates with its physiological characteristics, oil production and antioxidant activity [46].…”