## 4 Discussion
### Kinetics of Resveratrol Increase during Post-Pruning Storage  
Accumulation on trans-resveratrol during the storage period is reported on in many studies [5; 28; 29]. Recent research showed that increases in trans-resveratrol content in shoot samples were due to biosynthesis pathway genes (PAL, C4H, 4 CL, and STS), present in abundance, especially the STS gene (forming trans-resveratrol), which was induced over the first 4 weeks of storage. Vine shoot storage time after pruning exposed an \"important\" trans-resveratrol accumulation, with a maximum 181-fold induction on day 70, and a maximum average for days 71-75, as can be seen in Table 2. To highlight the increase in trans-resveratrol content over the 90 days, the average results were calculated for 5 consecutive days; the results are displayed in Figure 1.  
Day 1 of the analysis was when the vine waste was collected from the vineyard; the first sample was dried and then extracted with an ethanol-diethyl ether mixture. The minimum value of trans-resveratrol content in vine shoots was registered on day one of the analysis (14.93 mg/kg D.W.) and the maximum value was registered on day 70 of the analysis (2712.86 mg/kg D.W.). [PERSON] et al., (2017) reported an increase in the concentration of trans-resveratrol and other non-volatile phenolic compounds on samples of vine waste for two Spanish varieties (Airen and Cencibel) after different times of storage (one month, three months, and six months). After one month, the concentration of trans-resveratrol in the Airen variety was 77.10 \(\pm\) 11.29 mg/kg D.W. After three months, the concentration almost doubled (151.60 \(\pm\) 9.42 mg/kg D.W.), and a slight increase was recorded after six months (170.44 \(\pm\) 3.82 mg/kg D.W.). The sample from the Cencibel variety followed the same way regarding increasing the concentration of resveratrol, with 50.41 \(\pm\) 2.74 mg/kg D.W. after one month. After three months, the concentration was four time higher (224.83 \(\pm\) 29.64 mg/kg D.W.); after six months of storage, a slight increase was recorded (227.00 \(\pm\) 6.03 mg/kg D.W.) [28]. For the Airen variety, the increase in resveratrol content from one month to three months was 196% and 448% for the Cencibel variety. According to the results of this study, the trans-resveratrol content increases only until days 70-75, after which, it decreases slightly. However, the content of trans-resveratrol per kilogram of dry matter was much higher for the Feetasca Neagra variety than for the Spanish varieties, which reached up to 923.10 mg/kg D.W. after one month. Trans-resveratrol increase can vary widely due to the synthesis of the monomer in plants, if influenced by various factors (variety of vine, climate, growing conditions, temperature, exposure to fungal and bacterial infections, UV irradiation season of pruning). These considerable increase in trans-resveratrol content in vine shoot samples can be attributed to the structural genes (PAL, C4H, 4 CL and STS), which are responsible for the biosynthesis of trans-resveratrol. They are induced during the storage period, and are active until the vine shoots are dry. It is believed that the drying process during the storage period might be \"sensed\" to be a stress signal by living plant tissues, resulting in biosynthesis of this monomer, and trans-resveratrol accumulates until the tissues are dry [14]. This is confirmed by the results that show that, at temperatures below 20 \({}^{\circ}\)C, trans-resveratrol accumulation is delayed. If the vine shoot samples are stored at \(-\)20 \({}^{\circ}\)C, trans-resveratrol is not induced [14].