Over the past few decades, both wildfires and human-sparked fires have ravaged Mount Parnitha, destroying the mountain’s unique natural ecosystem, applying pressure to its flora, and subjecting the vulnerable populations of Sideritis raeseri subsp. attica to excessive stress. The present study aims to establish an efficient micropropagation method starting from in vitro-grown seedlings. The in vitro germination study carried out during the production of seedlings revealed a higher germination rate (34.0% and 37.0%, respectively) at 20.0 °C and 25.0 °C. The in vitro-derived seedlings studied were used as the starting material for the establishment of various media. Murashige and Skoog (MS) media, hormone-free and containing 0.5 mg L⁻¹ 6-benzyladenine (BA), led to the satisfactory (84.0–89.0%) establishment of plantlets. During the multiplication phase, the study used BA in conjunction with α-naphthaleneacetic acetic acid and four different cytocinins (BA; kinetin (KIN); 6-(γ-γ-dimethylallylamino) purine; zeatin) at low concentrations (0.5 mg L⁻¹). During the second subculture, a high multiplication index (7.3 and 6.4, respectively) was found for the hormone-free MS medium and the MS medium containing KIN at 0.5 mg L⁻¹. Hyperhydricity took place on the media supplemented with hormones. Rooting occurred on the half-strength MS medium (51.0%). After two months, the plants’ survival rate stood at 100.0%, as did their ex vitro acclimatisation rate, which also registered at 100.0%. The present results could encourage not only the introduction of S. raeseri subsp. attica into the industry of floriculture as a new ornamental plant but also its ex vitro conservation.

Long term degradation of water quality from natural resources has led to the use of alternative water resources for irrigation that are saline. Saline water irrigation in floriculture for the production of nursery crops requires an understanding of plant response. The pot growth of four lavender species (Lavandula angustifolia, Lavandula dentata var. dentata, Lavandula dentata var. candicans and Lavandula stoechas) irrigated with water containing different concentrations of NaCl (0, 25, 50, 100 and 200 mM) was investigated under greenhouse conditions. Overall results of different plant growth variables were consistent, showing a significant decrease at 100 and 200 mM NaCl. All lavender species showed signs of salinity stress that included chlorosis, followed by leaf and stem necrosis at NaCl concentrations greater than 50 mM. L. dentata var. dentata showed the greatest plant growth followed in descending order by L. dentata var. candicans, L. stoechas and L. angustifolia. Despite greater growth of L. dentata var. dentata, the appearance of L. dentata var. candicans was “healthier”. In areas with saline irrigation water, L. dentata var. dentata and L. dentata var. candicans are proposed for the production of lavender nursery crops.

Seed ecophysiology and micropropagation of Clinopodium nepeta, an aromatic Mediterranean plant with pharmaceutical and horticultural uses was investigated. The optimum germination temperature of seeds stored at room temperature for 0, 6, or 12 months was 15 to 20 °C (100% germination completed in 10 to14 days) and cardinal temperatures were defined at 10 and 30 °C (80% to 82% and 62% to 76% germination, respectively). Six or 12 months of storage did not seem to affect germination, although 12-month-old seeds germinated at higher percentage and completed germination earlier at 15 °C than at 20 °C. Concerning micropropagation, shoot multiplication at subcultures of both adult plant- and seedling-origin nodal explants was tested on Murashige and Skoog (MS) medium supplemented with various cytokinin types, i.e., zeatin (ZEA), 6-benzyladenine (BA), kinetin (KIN), and 6-γ-γ-(dimethylallylamino)-purine (2IP), at various concentrations from 0.0 to 8.0 mg·L ⁻¹ . Both explant types presented a rather similar response during in vitro culture. Increasing concentration of all cytokinin types resulted in an increase in shoot number per responding explant (1.1–5.3) and in most cases a decrease in shoot length (0.6–3.4 cm). Increasing cytokinin concentration induced hyperhydricity to a number of shoots (0.1–6.5) per explant, mostly when ZEA and BA were used. Supplementing the MS medium with 8.0 mg·L ⁻¹ BA combined with 0.1 mg·L ⁻¹ 1-naphthaleneacetic acid (NAA) led to almost elimination of hyperhydricity and very satisfactory shoot production (80%/88% explant response and 6.5/7.5 shoot number per responding explant for seedling- / adult-origin explants, respectively). Alternatively, increasing the agar concentration to 12.0 g·L ⁻¹ and supplementing the medium with 8.0 mg·L ⁻¹ BA only, resulted in the same effect on eliminating hyperhydricity, such as the addition of NAA, and in the best shoot multiplication response achieved in this study (100% explant response, 9.4/9.9 shoots per explant for seedling-/adult-origin explants, respectively). Microshoots rooted abundantly (92% to 100%) on half-strength MS medium, either Hf or supplemented with 0.5 mg·L ⁻¹ to 4.0 mg·L ⁻¹ indole-3-butyric acid (IBA). The addition of IBA to the rooting medium, regardless of its concentration, affected only the root length by increasing it 2- to 3-fold. Microshoot clusters produced on multiplication media rooted at 96% when cultured on Hf half-strength MS medium. Rooted microshoots and shoot clusters survived at 80% to 100%, respectively, after ex vitro acclimatization in peat:perlite 1:1 (v/v).

Dyckia brevifolia is an endangered plant used for ornamental purposes. As no references to the in vitro propagation of the species exist, the present study aims at investigating the possibility of an efficient micropropagation protocol. Seeds collected from mother plants were germinated at high percentages (84–86%) at a range of 15–25 °C, without any pre-treatment, and demonstrated their highest germination speed index (191.51) at 25 °C. In vitro-grown seedlings were used as the starting material for micropropagation on solid, or liquid, MS medium, supplemented with a variety of concentrations of cytokinins (BA, KIN or 2IP). Shoots and leaves were used as starting explants. Liquid media supplemented with BA or 2IP at 1.0 mg L⁻¹ led to high multiplication rate and 2.7, or 2.3, lateral shoots were regenerated while on 2IP a high percentage (77.5%) of rooting occurred at the same time. Rooted microshoots were acclimatised ex vitro at 100% and acclimatised plants were transplanted in pots where they grew with a survival rate of 100% after two months. The in vitro propagation protocol presented in this study could enhance the large-scale propagation use of D. brevifolia as an ornamental plant and, simultaneously, contribute to the ex-situ conservation of the species.

Cerastium candidissimum Correns is an endangered species. Nevertheless, its ornamental characteristics make it an ideal candidate for commercial use as a new ornamental and landscape plant. As there are no references to the in vitro propagation of this species, the present research aims to comparatively investigate the potential that in vitro propagation may have of three different populations of the plant, from Mounts Parnassos (PS), Parnitha (PR), and Hymettus (HM), respectively. The establishment of the initial cultures took place by cotyledonary- and stem-node explants, excised from in vitro grown seedlings, on Murashige and Skoog (MS) media, without hormone (Hf), or with 0.5 mg L⁻¹ 6-benzyladenine (BA). The shooting percentage was higher in the case of the PS population (97.6%). It was also higher for stem-node explants (93.9%). The multiplication phase took place on Hf MS, or on MS containing BA (0.5 and 1.0 mg L⁻¹), with or without 0.1 mg L⁻¹ 1-Naphthaleneacetic acid. The higher shoot production was observed in the PS and PR populations (88.0% and 76.9% shooting, with 3.1 and 2.7 shoots/explant, respectively). Micro-shoots rooted at high percentages on half-strength MS (80.0–100.0%). Successful acclimatisation (95.0%) was established on peat: perlite (1:1 v/v). Moreover, an efficient alginate-encapsulation procedure was developed from PS stem-node explants, using a 3.0% w/v sodium alginate and 14.7 g L⁻¹ calcium chloride solution. Alginate beads exhibited a higher shoot proliferation (3.8 shoots) after 60 days of storage at 4.0 °C and a 50-day growth on Hf MS than non-encapsulated in vitro node-explants did. The presented protocol of in vitro propagation of C. candidissimum could facilitate the exploitation of the species by the floricultural industry and contribute to conservation strategies.

Micropropagation of Arbutus unedo, A. andrachne, and A. x andrachnoides could facilitate their use as ornamental, forestry and medicinal plants, while the use of in vitro-grown seedlings as stock material could solve contamination and seasonality problems. Seeds germinated at high rates (87 – 99%) at 15ºC on half-strength Murashige and Skoog (MS) medium after 24 – 30 d, depending on the species. Nodal explants were excised from 2-month-old seedlings grown on MS medium or on woody plant medium (WPM) salts supplemented with 100 mg l^–1 myo-inositol, 1.0 mg l^–1 thiamine, 0.5 mg l^–1 pyridoxine, and 0.5 mg l^–1 nicotinic acid, containing 1.0 mg l^–1 indole-3-butyric acid (IBA). Multiple shoots were produced from each initial culture, and from subsequent sub-cultures on MS medium or on WPM containing 2.5 or 5.0 mg l^–1 zeatin (ZEA). The use of thidiazuron (TDZ) at 0.2 or 2.0 mg l^–1, instead of ZEA, resulted in a reduced response and fewer shoots per explant. In addition, these TDZ-treated shoots had malformations and were very short, making them unsuitable for multiplication. The rates of multiplication on both media containing 2.5 or 5.0 mg l^–1 ZEA were six- to seven-fold higher than on TDZ-containing or hormone-free media. MS medium resulted in higher rates of shoot production than WPM (4.4 – 7.8 vs. 2.2 – 5.3 shoots per explant, respectively, depending on the species and concentration of plant growth regulator) for cultures with a higher shoot proliferation potential. In contrast, WPM induced higher rooting percentages and more roots per micro-shoot (82 – 97% and 4.5 – 8.5, respectively, depending on the species and IBA concentration) compared to MS medium (42 – 64% and 3.1 – 4.1, respectively). A. x andrachnoides had a proliferation potential (4.6 shoots per explant on average on both media and ZEA concentrations) that was between the two parental species (5.9 and 3.4 shoots per explant for A. andrachne and A. unedo, respectively). Ex vitro acclimatisation and survival of plantlets in a 1:1 (v/v) mix of peat:perlite was highly successful (92 – 100%).