# Impact of Environmental Factors on Stilbene Biosynthesis
## 3 Impact of Environmental Factors on the Biosynthesis of Stilbenes
### Other Environmental Factors  
Stilbene biosynthesis is affected by a wide array of abiotic environmental factors besides the ones mentioned above, and extensive literature has been produced regarding this subject. Past reviews identified, aside from UV, light, wounding and temperatures, drought, ultrasonication, ozone, salinity, pesticides, and soil nutrient content as important abiotic stress sources capable of modulating stilbene biosynthesis [3; 5; 6; 20; 330]. Water stress has been shown to produce conflicting results on stilbene biosynthesis in grapevine, with either an increase [96; 331] or decrease [332; 333] in stilbene content and different behaviors among resveratrol, piceid, and vinferin content in different cultivars, suggesting a pivotal role for genotype [334]. The diversity in polyphenol composition and its changes in response to drought has been recently investigated on a large panel of grapevine cultivars by [PERSON] et al. [335]. The effects of ozone on stilbene biosynthesis, on the other hand, have been known for several decades. Ozone was observed to increase STS activity, as well as the biosynthesis of pinosylvin and pinosylvin 3-methyl ether in Scots pine seedlings [336]. It was also reported to induce an augmented transcript level of the _PMT_ gene in Scots pine needles [221]. Sitka spruce (_Pica stichensis_ (Bong.) Carr.) stem bark tissues have also been observed reacting to ozone treatment with an increase in resistance to pathogens, although no alterations in the levels of the stilbene glucosides astringin and isorhapontin were recorded [337]. _Vitis_ spp. were also investigated through cell cultures [338] and post-harvest treatment [183; 191], recording general increases in _trans_-resveratrol, piceatannol, pterostilbene, viniferins, and increases in _STS_ expression in response to ozone (although only on ozone resistant phenotypes). Further investigations of _STS_ expression in transgenic tobacco plantsin combination with its promoter (\(VstI\)) and the \(\beta\)-glucuronidase (GUS) reporter gene resulted in 11-fold GUS expression following a single ozone pulse and induction of the Vst1 promoter in several tissues [339]. Recent reviews also covered the elicitation of stilbenes due to ozone [5; 20], a topic that was later expanded by [PERSON] and colleagues [340] observations published in 2019 regarding the combined effects of elevated ozone, temperature, and nitrogen on stilbene concentrations in Scots pine. They reported that warming does suppress the induction of some stilbene compounds/derivatives in ambient ozone levels. Another important abiotic stress is salinity. Salt stress represents a devastating constraint to plants' development processes and physiological homeostasis, causing membrane disorganization, cytoplasm alkalinization, ROS induction, transport perturbations, tissue proliferation, and perturbations to photosynthesis, ionic and ionic-related channels [95]. Sodium chloride (NaCl) salt stress is known to strongly delay the rapid induction of \(STS\) and resveratrol production in _V. rupestris_ ([PERSON]) cell cultures, with a late increase in stilbenes. _V. riparia_ (Michx. ), instead, does not seem to respond to salt stress [341]. A recent experiment on _V. vinifera_ plantlets subjected to NaCl treatment revealed that the salt-tolerant cv. Razegui did not show important variations in stilbenes biosynthesis, while the salt-sensitive cv. Syrah showed an increase in _trans_-resveratrol, _trans_-piceid, and _cis_-piceid, probably to cope with the higher oxidative disturbance [95]. Resveratrol seems to possess an important role in salt adaptation, as it was found that the application of resveratrol in combination with \(\alpha\)-tocopherol to _Citrus aurantium_ L. seedlings reduces NaCl membrane permeability, lipid peroxidation, and pigments degradation, besides reducing H\({}_{2}\)O\({}_{2}\) accumulation in leaves and restoring the reduction of photosynthesis induced by NaCl [342]. Different salts also affect resveratrol production in grapevine.