## 3 Results and Discussion
### Biometric Measurements of the Stevia Plants
These results suggest that it is possible that irrigation has a more substantial role in the formation of sugars in stevia in warmer climates. The irrigation of stevia decreased the concentration of phenolic compounds in stevia leaves. In July, the lowest concentration of phenolic compounds was detected in the sample 1 W (185.62 mg\(\cdot\)100 g\({}^{-1}\)) and greatest in the sample 0 W (270 mg\(\cdot\)100 g\({}^{-1}\)). Similar tendencies were noted in the samples gathered in September, but the total concentration of phenolic compounds in all the samples was greater at that time. In September, sample 0 W was characterised with the highest concentration of phenolic compounds (337.88 mg\(\cdot\)100 g\({}^{-1}\)), while samples NR, 2 W and 1 W were characterised with lower, similar content of phenolic compounds in the range from 241.03 (for NR) to 260.57 mg\(\cdot\)100 g\({}^{-1}\) (for 1 W). In the study by [PERSON] et al. [30], stevia plants grown with a deficit of water were also characterised with a higher total concentration of phenolic compounds, which could possibly result in greater health benefits due to the consumption of these plants or products from these plants. The major phenolic compounds found in the stevia leaves are hydroxycinnamic acid and quinic acid, characterised with valuable therapeutic properties [3]. General studies about a variety of different plants, mostly from the _Asteraceae_ family, have shown that increases in the production of various phenolic compounds is a typical response of many of the plant species to drought stress; therefore, it is not surprising to see these results in the studies about _Stevia rebaudiana_ plants [31; 32; 33]. In July and September, the highest concentration of ascorbic acid was determined in 0 W, while lower content was detected in 1 W and NR. The concentration of ascorbic acid had not changed from July to September as much as content of phenolic compounds, but small changes in the range up to 5-6% could be noted. In July, the highest concentration of ascorbic acid was determined in sample 0 W (139.99 mg\(\cdot\)100 g\({}^{-1}\)) and the lowest was detected in sample 1 W (121.02 mg\(\cdot\)100 g\({}^{-1}\)). In September, sample 0 W was still characterised with the greatest concentration of ascorbic acid (143.30 mg\(\cdot\)100 g\({}^{-1}\)) and NR had the lowest content of ascorbic acid (124.66 mg\(\cdot\)100 g\({}^{-1}\)). It is also important to note that only in the sample NR did the concentration of ascorbic acid decrease from July to September. On the other hand, a study by [PERSON] and [PERSON] [34] revealed that drought stress can decrease the total concentration of ascorbic acid in stevia leaves over two-fold, which is contrary to the results acquired in our own study in Poland. These results might indicate that possibly stevia grown in Poland, even without additional irrigation, is not under sufficient drought conditions, which can induce loss of the ascorbic acid in the stevia leaves. A high concentration of vitamin C in stevia could possibly show viability of utilising these plants as an animal fodder, which was proven by [PERSON] et al. [35] and [PERSON] and al. [36], who have shown that stevia and production waste of stevia products can be consumed by pigs and poultry.