The physiology of grapevine, like that of any other plant on our planet, consists of two processes: accumulation and transport. To obtain quality raw material for winemaking, it is necessary to control both. Picture a working factory. That's the grape leaf. Inside the leaf, processes of organic compound synthesis are constantly taking place. For the factory to function, raw materials must be sourced and delivered. This is the job of the root system and the vascular (conducting) system. And while you already know quite a lot about nutrient uptake by the roots (you feed the vineyard, monitor for diseases and pests), the vascular system rarely gets attention until necrosis is discovered.
The vascular system is your logistics — without it, fertilizer won't reach the leaf, and disruptions in its operation happen more often than we'd like. And the scariest part is that we usually don't notice them. In most cases, the cause of these disruptions is vessel blockage by salt deposits from the very fertilizers we apply, or by the waste products of pests; sometimes it happens due to mucilaginous buildup on vessel walls, as a consequence of viral activity or improper preparation for winter dormancy. To prevent these undesirable phenomena, we used a system of foliar (non-root) treatments with phyto-preparations.
This includes, for example, salicylic acid, which effectively combats vessel blockage. Of course, that's not its only function, but it's an important one. Uptake and delivery of nutrients is only half of the process. At the same time as production is happening at our factory (the leaf), processes of outflow of the produced organic compounds (photosynthesis products) and accumulation are also taking place. Everything accumulates in the leaf as well. So it's not just a factory, but also a warehouse. That's why it's important to maintain the health of the leaf apparatus. The bigger and healthier the leaf, the more sugars, phenols, acids, and proteins will be produced and stored.
Here we already need to strike a balance between the size of the warehouse and the planned yield. Why does this matter? Because at the onset of veraison (color change), the outflow processes will start to dominate over consumption and production, and the plant will live off its stored reserves alone. If those reserves aren't sufficient, don't expect quality. Figuratively speaking, first we work for the leaf, then the leaf works for us. The preparations we selected also serve the function of preserving leaf health and maintaining its functioning. To this end, they include both ready-made chlorophyll (which essentially acts like a blood transfusion during a critical period) and hormones that stimulate the plant itself to increase its own chlorophyll production. Of course, the effect is quite dramatic, but remember — you can't make something out of nothing. The plant must be well-fed for such techniques to work at maximum effectiveness, so the soil must not be neglected.
The hardest part is keeping the leaf intact during critical stress periods. The most common one in our southern region is hydro-stress (water/heat stress). The same salicylic acid works to minimize its impact — it lowers the temperature of the grapevine's cell sap through intracellular reactions, and it also acts as a chelating agent, converting phytotoxic metal compounds that have accumulated in the cells (from conventional fertilizing) into safe chelates of trace elements needed for nutrition. For maximum protection against temperature stress, an additional phyto-preparation is used. It thickens the cell sap, forming colloidal water that doesn't evaporate but can still participate in exchange and dissolution processes. This preparation also reduces the rate of acid breakdown caused by high temperatures.
At this stage, a second very important process is also taking place — the establishment of the future harvest. By the end of flowering, we need to ensure the maximum possible number of cells in the future berries, because after that it will no longer be possible to change this — only to stretch the cells that already exist. Seeds are the main means of continuing the species for the grapevine, and like any plant, it strives to provide them with everything necessary for a worthy future. The preparations we use contain four key components for this: boron, calcium, silicon, and phytoauxin. Calcium is needed as a trigger — even just one ion needs to reach every cell to avoid uneven distribution later on (and calcium is also responsible for skin firmness, coloring, and even ripening). Phytoauxin and boron act as a locomotive, pulling all the nutrition toward the point of active growth (into the crop, or toward the shoot tips before their formation, or toward the growth points of the root system). Silicon (much like calcium) is a safety line: if there isn't enough auxin or boron, it will substitute for them and become that locomotive itself.
To monitor the condition of the plants, we regularly carry out tests in the vineyard, studying how the dry matter content changes in the leaf and in the berry.
From the moment the berry forms, outflow processes intensify, and by the onset of veraison (color change) they come to dominate over consumption processes. At this point, the dry matter content in the leaf should gradually decrease, while in the berry it should increase. Everything stored in the "warehouse" should move into the berry. In reality, not into the berry as such, but into the seeds. That's why the number and size of the seeds can already tell us the potential quality of the raw material for winemaking. At this same moment, we have a very short window of time in which we can work on the phenols — no more than a week. A day early, a day late, and the timing is missed — the techniques are no longer effective.
We use phyto-preparations for this. In addition to everything mentioned above, they include an extra complex of trace elements and hormones that stimulate the formation of flavor and aroma compounds. With this technique, we shape the future quality of the wine right on the vine. And given that this also stimulates the vascular system and the signal to move reserves toward the seed, we manage to drive nearly all the reserves out of the leaf and into the berry. After that, it's enough just to maintain the outflow. But that doesn't mean we should stop there. The longer we keep the leaf functioning, the more of these compounds will be produced, and the higher the phenol content in the berries will be. That's why we protect the leaf until the very end. After harvest, we don't stop the treatments. A leaf depleted by this technique has small reserves "in storage," but winter is still ahead.
Sugars are needed for successful overwintering, wood ripening, and the filling and preservation of buds. That's why, before leaf fall, we carry out two more treatments: the first phyto-preparation to restore the chloroplasts, and the second to fully drive the sugars out of the leaf into the wood, buds, and root system. These can be combined into a single tank mix. Here you need to be guided by the condition of the plants. If they're heavily depleted, it's better to split the treatments; if reserves are plentiful, they can be combined. Again, everything should be decided based on diagnostic results — you'll never be able to tell the difference visually. Through this approach, we managed within a single season to eliminate a nutrient imbalance, improve berry quality, and get rid of sodium phytotoxicity, which also lowers wine quality. It's also worth noting another important role these preparations play — strengthening the plant's immune system.
Against viruses, a plant can only fight on its own. To this day, not a single plant protection product has been developed that fully eliminates this type of parasite. The phytohormones included in this line of preparations are obtained by extraction from plant raw material, not synthesized, and so they carry out their functions exactly as a hormone produced by the plant itself would. Without causing phytotoxicity or hormonal disruption, they take part in the process of releasing marker proteins that identify and tag virus-infected cells for subsequent destruction. As part of a comprehensive therapy for viral diseases, this brings significant improvement to the overall condition of the vineyard and helps preserve its productivity over the long term.