What is the link between root temperature, vine reserve and berry ripening?

Fruit ripening

If you read this blog you are probably interested in understanding the complexity of vine response to contrasted environmental conditions. Everyday scientific results shed new light on plant mechanisms which, if they are properly understood, can help the winegrower optimizing his practices. Today, we discuss the relationship between :root temperature, vine reserve dynamics and berry ripening.

Why is that important?

Earlier Studies linking carbohydrate and nitrogen reserves in grapevines with vegetative growth and fruiting responses suggest that monitoring stored reserves at dormancy could provide an advanced indication of yield and growth potential in  the following season .  In the context of climatic changes understanding how practices affect root  temperatures, which in turn affect reserves mobilization can be critical to  adjust  vineyard  practices according to site specific conditions.

Such knowledge can directly benefit vineyard performance  through the maintaining  of  proper carbohydrates supply. Thus, with new finding it becomes possible to revisit soil practices while leveraging new tools to monitor key parameters affecting  vineyard sustainability

What do we already  know?

  1. Generally, soil warming promotes utilisation of non-structural carbohydrates in the roots, and increases shoot growth rates and flower number. In contrast, soil cooling can increase the abscission of flowers and decrease fruit set.
  2. Soil temperature variations effects are  being conditioned by the carbohydrate reserve status of the plant. Vineyard soil temperature up to veraison generally follows the seasonal increase of atmospheric temperature. However, daily and seasonal variation is also influenced by practices such as mulching or  soil shading depending upon canopy dimensions. Thus, human practices  can alter the temperature dynamics of the soil.

How do soil and canopy management alter soil temperature  ? and in turn, how do soil temperature modulate carbohydrate reserve changes during spring and  leaf area development ? To further understand the interplay between soil temperature and vine carbohydrates reserves,  a team of researcher led by Holzapfel investigated specific effects of varying soil temperatures on vine response.This study was conducted on mature, field- grown grapevines V. vinifera L. ‘Cabernet Sauvignon’ over two growing seasons, to examine the carbohydrate reserve dynamics and growth responses to soil temperature as modified by plastic sheet and straw mulches.

Figure 1 shows that surface treatments significantly influenced root zone temperature to a depth of 30 cm. Temperatures under the warm treatment (plastic sheet) are up to 10°C higher than under the cool treatment (plastic/straw).

Berry ripening

Figure 1: soil temperature profiles at -30 cm  (adapted from Holzapfel et al, 2016)

What the researchers found?

  1. The carbohydrate root reserve concentrations declined from budbreak to flowering by more than half, with the increases in soil temperature considerably elevating the mobilisation of the root reserves. (Figure 2)

  1. The implemented soil temperature regimes had a minor influence on canopy growth and reproductive development. Warmer soil temperature induced  an  advancement in berry ripening (high brix values are reached earlier).Berry ripeningFigure 2: seasonal profile of  root non-structural carbohydrates (adapted from Holzapfel et al, 2016)

These findings suggest that not only ambient temperature can affect berry maturation under similar yield levels. The root environment also has an influence on fruit development.

Take home

Soil management practices, through their effect on root temperature will  changes reserve dynamics and also influence berry maturation and composition. Think about it next time you are defining a strategy for soil cultivation practices!

If you want to track the effects of soil cultivation:

  • on vine reserve:  you can monitor wood reserves variations (Physiocap)

On advancing  fruit ripening: you can track  sugar loading profiles. (See previous article).

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Posted by Vintage Report

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