## Results and Discussion  
### Fresh Yield, Growth Response and Colorimetric Attributes  
Plant final height and leaf area were influenced by salinity and genotype with no significant salinity \(\times\) genotype interaction, whereas the leaf number, leaf fresh yield, as well as dry shoot biomass were affected by salinity \(\times\) genotype interaction (Table 1). The significant depression of plant growth parameters (leaf number and area, leaf fresh yield and dry biomass) with increasing salinity level in the nutrient solution has been demonstrated in previous greenhouse studies on cardoon/artichoke and spiny chicory [23; 24]. Intra-specific cultivars/genotypes may develop different salt-tolerance mechanisms depending on the severity of stress in terms of concentration and time of exposure [21; 22]. This was the case in the current study since the fresh yield and dry biomass of both genotypes decreased with increasing salinization, although the red-pigmented genotype was less affected than green-pigmented one at 20 and 30 mM NaCl. Specifically, the percentage of fresh yield reduction in comparison to non-salinized control plants was 7.8%, 16.5% and 48.6% in red perilla and 22.0%, 44.4% and 78.0% in green perilla at 10, 20 and 30 mM NaCl concentration in the nutrient solution, respectively (Table 1). This differential genotype response was also confirmed for dry shoot biomass and leaf number. The higher sensitivity of green perilla to salinity is attributed to the higher sodium concentrations in leaf tissue compared to red perilla (Table 2). Averaged over salt treatment levels, red perilla was able to accumulate 48.5% less sodium and to maintain potassium-to-sodium ratio (salt tolerance indicator) two-fold higher than the green cultivar (Table 2). The improved crop performance of red perilla in terms of fresh yield and dry biomass at the three levels of salinity stress applied could be associated to decreased stomatal resistance, which enhances the net CO\({}_{2}\) assimilation rate (data not shown), and consequently plant vegetative growth and productivity. Moreover, it is worth noting that the tested genotypes demonstrated marked differences in their fresh yield and dry biomass potential. Under non-saline conditions, the fresh and dry yield of green perilla was respectively 43% and 68% higher than that of red perilla (Table 1). This is in agreement with previous research which demonstrated that green perilla cultivars generally grow faster than red ones under both controlled and open-field conditions [16; 25]. Among the physical properties of leafy vegetables that strongly influence consumer preference, acceptability and choice making is visual appearance, in particular leaf color [26; 27]. The coloring pigments (i.e., carotenoids, phenols, anthocyanins and betalains) may also be considered as an indicator for estimating the antioxidant properties of edible and medicinal plants, where red and dark green colored leafy vegetables are richer in nutrient content than lighter colored vegetables [28]. This was the case in the present study where genotype was expectedly the determining factor affecting Perilla leaf color, given that cultivars of distinct colorimetry were examined. The highest redness values recorded in red perilla were expectable since this chemotype is characterized by high presence of specific pigments (phenols and anthocyanins) involved in leaf coloration. Less significant was the effect of salinity on leaf brightness (L*), which overall increased in response to increasing NaCl concentration in the nutrient solution (Table 1). The predominance of the genotypic effect completely masked the effects of salinity on color components a* and b*. However, a closer look at color component a* shows that in the green cultivar it dropped in response to the 30 mM NaCl treatment, denoting loss of greenness and a transition towards the achromatic center of the CIELAB chromatic sphere [29].