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Pyrus spinosa Forssk. (almond-leaved pear) is a wild-growing native tree of the hilly countryside of Greece, which has recently gained interest for its valuable endogenous substances. In the present work, the determination of the total phenol content (TPC) and antioxidant capacity (AC) was carried out during 2021 and 2022 in leaves from 32 genotypes of mature wild-growing trees at four different locations of Central Macedonia District, Greece: Agia Anastasia, Chalkidiki, Lagadas and Pieria. The measurements taken from the leaf samples of all genotypes revealed a strong positive linear correlation between TPC and AC (R2 = 0.772). Two genotypes from Agia Anastasia, coded as AA2 and AA3, were comparatively the richest in TPC (44.86 for AA2 and 46.32 mg GAE/g fresh weight for AA3) and AC (70.31 and 71.21 μg AAE/g fresh weight for the same genotypes). For these two genotypes of high TPC and AC, an efficient micropropagation protocol was developed to preserve and multiply this valuable germplasm. Newly emerged shoot tips were excised from winter shoots and, after disinfestation, they were established on a modified Murashige and Skoog (MS) nutrient medium with 5 μΜ of 6-Benzyloaminopurine (BAP). For shoot multiplication, explants from clean cultures were transferred to Pear Medium 1 with 5 μΜ of BAP. The effect of the nutrient medium was tested by using five different nutrient media (modified MS, Pear Medium 1, Pear Medium 2, DKW and WPM) supplemented with 5 μΜ of BAP. Pear Medium 1 was the most effective in shoot formation. Among the four different BAP concentrations (0, 5, 10 and 20 μΜ) used in Pear Medium 1, 5 μΜ of BAP resulted in the production of the significantly highest number of shoots (22.7 shoots per explant, 2.4 cm long). The exposure of cultures to 10 μmol·m−2·s−1 for one week under light irradiance followed by 35 μmol·m−2·s−1 for four weeks increased both the number and length of the shoots produced. A 20-s dip of the shoot bases into 49.0 μΜ of Indole-3-butyric acid (IBA) in EtOH equally affected rooting in a modified rooting MS (79%) and Pear Medium 1 (80%). The root system developed better in the modified rooting MS medium (mean number of roots of 2.7 with a length of 3.9 cm). The acclimatization of the plantlets was successfully carried out (high survival rates five weeks after their establishment) on a perlite substrate under controlled environmental conditions.

Carbon sequestration by forests and storage in biomass has gained great interest globally in climate change mitigation. Resinous pine forests act as ideal carbon sinks because, in addition to capturing atmospheric CO2 for biomass production, they produce resin (resin concentration in C: 77.17% w/w), contributing further to the mitigation of the greenhouse effect. Greece until the 1970s was considered one of the main resin-producing countries of Europe, due to the quantity and quality of resin products collected from natural populations mainly of Pinus halepensis Mill. Previous and current research has shown that resin production is a genetically controlled trait (h2 > 0.70) that exhibits great variability among trees (resin 0.5–33.0 kg per tree and year). The above led to the genetic selection of P. halepensis genotypes with constant over time high resin yields (≥20 kg per tree and year) and consequently greater atmospheric CO2 sequestration for more effective counteracting climate change but also for economic reasons for the benefit of resin producers. These high-yielding genotypes were cloned through grafting on P. brutia rootstocks and became potential trees for establishing commercial pine plantations. Thus, one hectare of commercial plantation of 500 P. halepensis trees, with a resin yield of 20 kg per tree, is expected to sequester 28.31 tn CO2 per year (instead of 2.82 tn of CO2 per year of a natural stand of 400 P. halepensis trees based on a resin yield of 2.5 kg per tree), at the productive age of 25 years. In this case, commercial plantations with improved genotypes of P. halepensis have great potential not only in mitigating the concentration of CO2 in the atmosphere, but also in restoring degraded marginal areas and arid soils, and at the same time can offer social and economic benefits to the local communities.

The market demand for interesting varieties and cultivars of Ilex aquifolium necessitates the exploration and sustainable exploitation of plant individuals thriving in nature without human care. In this work, an effort was made to develop a simple and reliable protocol for vegetative propagation of I. aquifolium plants, with desirable-for-market characteristics, grown in a mountain area of Halkidiki, Greece, and at the same time to proceed with their genetic identification using molecular markers. From these plants, new plants were vegetatively produced which afterward were used as stock plants for providing the needed shoot cuttings for the experiments of rooting and leaves for their genetic analysis. Factors studied in formulating a propagation protocol included the season of cutting collection and the application of 0.2% 1-naphthaleneacetic acid (NAA), as well as the type of shoot cuttings (terminal, subterminal) and the application of auxin. It was found that application of NAA was crucial for rooting response and number of roots formed, whereas the season effect was not significant on rooting. Terminal cuttings treated with 0.2% NAA exhibited the highest rooting percentage (100%) and formed abundant roots (25.7) compared to subterminal ones. All rooted cuttings, after being potted and transferred to acclimatization greenhouse, were successfully hardened. In the spring of the next year, the produced plants blossomed abundantly and formed fruits (bright red berries) presenting their characteristic ornamental appearance that was maintained until Christmas. For the identification procedure, the genotypic profile of the stock plants was also investigated by inter-simple sequence repeat (ISSR) genetic analysis, revealing that they were genetically the same both among themselves and when compared with a certified I. aquifolium ‘Agrifoglio Commune’ individual, but they differed genetically from I. aquifolium ‘Argentea Marginata’ and I. aquifolium ‘Hellas’.

Rosmarinus officinalis L. belongs to the Lamiaceae family and is cultivated worldwide due to its diverse uses as an ornamental evergreen shrub in gardening, as well as a food seasoning and a natural medicine. The present research was conducted to study the morphological traits of seven wild-grown rosemary populations in Greece, as well as the propagation of two selected populations with the most desirable ornamental characteristics, by the use of shoot cuttings and in vitro cultures. From the study of the morphological traits of the seven populations, those with interesting features were grown in the areas of Amaliada and Piperia and, thus, were chosen for studying their propagation. Rooting of the shoot cuttings was carried out during the four seasons of the year, using potassium salt Indole-3-butyric acid (K-IBA) at concentrations of 0.5 and 1 g·L−1, in various substrates under the intermittent mist or fog system. It was found that the shoot cuttings rooted easily in all four seasons, but there were better results for the population of ‘Piperia’ in autumn, with 1 g·L−1 K-IBA (80%), and ‘Amaliada’ in spring, with 0.5 g·L−1 K-IBA (82.5%), while higher rooting percentages were achieved in the fog system, on a substrate consisting of perlite and peat, in a ratio of 2:1 (85%). For the in vitro cultures, shoot tips excised from the two selected populations were successfully disinfested by pre-soaking in an antioxidant solution and then, by sterilizing them in 0.6% (w/v) NaOCl, followed by transferring them onto a Murashige and Skoog (MS) nutrient medium. ‘Amaliada’ cultures proved to be the most productive population (2.1 shoots per explant), with the highest shoot formation frequency (91.6%), when cultivated on the MS nutrient medium without plant growth regulators. For ‘Piperia’ cultures, the highest shoot formation frequency (66.6%) was achieved on the MS nutrient medium supplemented with 0.25 or 0.5 mg·L−1 6-Benzyloaminopurine (BAP) and 0.1 mg·L−1 Indole-3-acetic acid (IAA). Spontaneous root formation frequency was noticed on the MS nutrient medium, containing 0.5 mg·L−1 BAP and 0.1 mg·L−1 IAA, for both ‘Amaliada’ and ‘Piperia’ cultures (50% and 41.6%, respectively) in a single stage, with root lengths of 7.1 and 5.3 cm, respectively. Rosemary plantlets, with roots formed in vitro after transplanting them in soilless substrate, were acclimatized adequately in the greenhouse environment (~70%).

Culture in vitro may result in anatomical abnormalities in the leaves, stems and roots of micropropagated plants. It may also affect major physiological processes, reducing the frequency of survival of micropropagated trees at the acclimatization stages. Two major strategies have emerged for the successful acclimatization of trees. The first involves encouraging micropropagated plantlets to become autotrophic and the second reducing water stress by changing culture environment. Both strategies may be applied in vitro at the preparatory stage, or ex vitro in the basic stage of acclimatization. The environmental factors involved in photosynthesis may be modified at the preparatory stage. Several modifications are possible, including decrease of the sugar concentration in the medium, increase in light intensity and modifications to gas exchange. Aerated vessels with bacteriological filters have been successfully used with several hardwood and conifer species. The beneficial effects of aeration have also been demonstrated from the initial stages of micropropagation onwards. However, the use of antitranspirants or surface-covering agents at the basic stage has not proved to be very efficient for woody plants. Water and mineral uptake, root system development and the prevention of infection by soil pathogens, are markedly improved by the addition of mycorrhizae. Trees that form ectomycorrhizae may be inoculated in vitro, at the preparatory stage. However, the in vitro technique is unsuitable for trees that form mycorrhizae with endomycorrhizal fungi. For such species, mycorrhiza development is generally stimulated ex vitro, by transferring the plantlets to inoculated soil. Mycorrhiza development has been shown to increase the survival rate of almost all tree species tested, whether conifers, orchard or broad-leaved forest trees. Several of these techniques, used in combination, may facilitate successful acclimatization of micropropagated trees. However, the techniques used must be chosen on a case-by-case basis.

The suitability of conductivity measurement for monitoring growth in plant cell culture has been tested using suspended cells and genetically-transformed hairy roots of Atropa belladonna, and aggregated cells of Solanum aviculare. Other researchers have proposed that a constant ratio exists between increase in cell concentration (Δx) and decrease in medium conductivity (ΔC). In all cases studied in this work, Δx/ΔC was not constant over a wide range of cell densities tested in batch culture. With cell suspensions, Δx/ΔC decreased continuously during the growth phase from 3.4 to 2.5 g cm l−1 mS−1. For the hairy roots, the ratio between Δx and ΔC varied by as much as 4-fold during growth. The relationship between conductivity and growth for S. aviculare aggregates was found to vary depending on inoculum density. No simple correlation between conductivity change and cell growth was apparent for the plant-cell systems studied.

Procedures were developed for 'self-immobilisation' of Solanum aviculare cells to eliminate the need for artificial immobilisation supports. Depending on the cytokinin used in liquid medium, compact aggregates 0.4-2.0 cm in diameter were formed without dispersed cells also being present. Histochemical analysis showed that the aggregates were structurally organised to facilitate nutrient transport. Growth, sugar uptake and solasodine production were measured in shake-flask cultures. Most of the product was stored in the aggregates to reach a maximum concentration of 0.3% dry weight; this is between 1.5 and 10 times the levels reported for suspended cells under similar conditions. A substantial amount of solasodine was produced after growth ceased. The maximum rate of solasodine production was about 0.22 mg g-1 d-1. A simple air-driven bioreactor was tested for culture of the aggregates; solasodine yields were comparable to those measured in shake flasks.