Photosynthesis In Grapevines

Photosynthesis in Grapevines take place via their leaves 🌱.

Leaves 🍃 , thanks to chloroplasts that contain chlorophyll’s pigments, absorb sunlight energy ☀️ and convert the carbon dioxide and water into sugars and oxygen. (The stomata stores carbon dioxide from the atmosphere and the stems store the water).

This complex process that convert light energy into chemical energy is necessary for the growth and optimal ripening of the grapes. 

There are several factors that affect the rate of photosynthesis:

• LIGHT INTENSITY: Without sunlight the photosynthesis process cannot take place.

The optimal photosynthesis in grapevines takes place when the sunlight intensity is around 25,000 to 30,000 lux. Each single leaf in direct sunlight can absorb about 90% of the sun’s radiation.

〰️ Grape growers need to choose carefully the aspects and position 🌄 of the grapevines to get the most intensity, quality and duration light. Grapevines struggle in areas with limited hours of sunlight but growers can plant the vines near large bodies of water (rivers, lakes and seas) because photosynthesis can take place from reflected sunlight although the intensity of this light will not be high enough for the optimal photosynthesis. 

〰️ It is also very important to have good canopy management to produce a healthy crop according to the style of wine that each winery wants to produce. For this reason, it is necessary to understand the environment affecting the vine’s growth. If leaves are not exposed to the sunlight because vine canopies are too dense, the sunlight cannot penetrate and the leaves inside of these canopies will start getting yellow because photosynthesis cannot take place in those leaves. Furthermore, if grapes are exposed to a strong light intensity, they will get burned. 

• TEMPERATURE: TEMPERATURE IS A KEY FACTOR IN THE PHOTOSYNTHESIS PROCESS.

Taking in consideration that sunlight is a requirement for the photosynthesis process, temperature 🌡️ needs to be suitable:

〰️ Sunlight with cold temperatures can freeze the vine. (Winter, when temperatures are lower than 10ºC, vines are dormant until the spring when temperatures are getting high). 

〰️ Sunlight with high temperatures will make the vine transpire evaporating water through their leaves. That fact can be prejudicial in hot, dry and windy vintages conditions.

NOTE: Not all grape varieties need the same amount of warmth to grow and ripening. For example, Grenache would not be able to ripen its grapes in cool locations.

• WATER: Vines need water for photosynthesis.

The vines take the water up from the soil by the roots and is transported to the leaves via the xylem affecting the opening and closing of the stomata and, consequently, the entry of carbon dioxide from the atmosphere into the leaves. The amount of water available for photosynthesis is determined by the soil conditions and the rate of transpiration, humidity, mineral availability and stomata opening. 

• TRANSPIRATION: As humans, plants can evaporate the water absorbed by the roots in a process known as transpiration. 

The leaves of the grapevines evaporate large amounts of water during the growing season. The grapevine through the stomata can control the rate of moisture loss (transpiration). The stomata open in the day and close at night, although, can close during the day under some extreme conditions: hot temperature, strong winds…

• LEAF AGE:

The leaves of young grapevines can absorb photosynthesis rapidly. As grapevines get older, the leaves lose their colours and, consequently, the rate of photosynthesis declines.

Attending all these factors and how important is the photosynthesis process for growing grapes, winegrowers not only have to think about carrying the most appropriate techniques in the vineyard like pruning, trellising system and irrigation. However, growers need to understand the environment in which these vines are cultivated. 

Only, in this way, vines’ crops will be healthy and reflect a unique terroir.

Founder, 7p Aperitivo