Understanding and embracing wine entails having basic general knowledge about a variety of subjects – geography, history, chemistry and biology to name a few. While oenophiles only scratch the surface in some of these fields, others are more integral to the appreciation of wine and necessitate more involved inspection. To delve into a somewhat complex topic in the biology category, we will explore how a vine’s biology influences its grapes and vineyard locations.
Reminiscing about elementary school days is bound to conjure memories of long hours spent studying plants and learning the complex process by which they create energy. That procedure, known as photosynthesis, uses sunlight to convert carbon dioxide into water and sugar. Whether or not this transformation occurs at any given point in time depends on environmental factors. Sunlight is integral to the equation, so at night and on cloudy overcast days, photosynthesis cannot take place. Additionally, the rate of photosynthesis is influenced by the temperature, stagnating if it’s too cold or too hot. Ideal temperatures for optimal rates of photosynthesis range from the mid 60s to the high 80s.
When photosynthesis is not taking place, there are no sugars being produced for the vine to use for energy. So the vine resorts to another means of energy production, a process called respiration. In respiration, the vine metabolizes malic acid for energy. Malic acid is naturally present in the vine where it is stored in grapes. When the grapes are young berries, the level of malic acid is quite high, but the amount declines as the grapes develop. This is beneficial as grapes with excessive malic acid do not make good wine. On the flip side, though, if too much malic acid is consumed, the resulting wine is negatively affected as well.
Similar to photosynthesis, the rate of respiration is also directly related to the ambient temperature. As the thermometer rises, the amount of respiration increases progressively causing malic acid to be depleted at an expanding rate. This means that grape growers desire cool or even chilly nights to keep malic acid conversion low when respiration is occurring. The caveat is that places with those desirably brisk nights also tend to have shorter, cooler days which may impede the grapes’ ability to fully ripen. Therefore, regions with warm, pleasant days and cool, crisp nights are prime locations for vineyards. Scientifically, these areas are known as having considerable diurnal (daily) temperature differences.
All this being said, successful vineyards are located in far flung regions around the world in all types of climates experiencing an infinite number of weather conditions. So it is fair to say the aforementioned rule of thumb is simply a general guideline. Certainly, there are legions of vineyards and numerous grape varieties that challenge this notion by producing incredible wines in inhospitable environments. But the next time you enjoy a wine from an unusual location, you may not be surprised to note it is a place with warm days and cool nights. As the realtors say, it’s all location, location, location!
