Monday, October 1, 2012

Grapevine energy production as seen through the lens of a Generalized Supply Chain model

A supply chain identifies the key steps in the process within which a set of raw materials is transformed into products that are acquired by an end customer.  The supply chain normally extends into the practices of suppliers and into the habits of the end customer.  A representative supply chain is illustrated below.

Generalized Supply Chain Model (Source:

I propose that the production of energy in the grapevine can be viewed through the lens of a supply-chain schema and that, within this model, viticultural science takes on the mantle of supply chain management.  In this model, the core product is energy, in both its refined and raw form, and the core manufacturing process is photosynthesis.  I will elaborate on this proposal in two posts with this initial post focusing on the alignment of the grapevine energy supply chain with a generalized supply chain model.

Logistics is an integral part of the supply chain and is associated with the movement of raw materials, intermediate assemblies, and final products into and out of the manufacturing process. In some cases the demand is immediate and the product is moved directly to the customer where it is either consumed by the end user or used as a value-added input in a final assembly.  In other cases, production is shipped directly to a warehouse for allocation to the appropriate channel when the need arises.
Key logistics processes in the grapevine energy supply chain are transpiration and translocation.

Raw Materials
Inputs into the core production process of the supply chain are termed raw materials.  As indicated in my most recent post, the raw material inputs for photosynthesis are light, carbon dioxide, water, and nutrients.  The light energy is sourced from the sun and the carbon dioxide from the atmosphere.  Water is sourced from the soil (function of water accessibility, soil composition, soil drainage, and water retention) and is drawn up into the vine from the roots in a process called transpiration. Nutrients are brought into the roots by a combination of bulk flow, transpiration, and fungal action.

Photosynthates are produced in photosynthesis, a complex, two-stage process which produces the energy to fuel its own metabolic needs while also producing the raw, unprocessed energy elements that will be utilized by the vine to fuel its growth, development, and reproductive processes.  A detailed technical description of photosynthesis is beyond the scope of this blog (and the capability of the author) but a few framing remarks are in order.

Photosynthesis is a two-part process wherein (i) the green parts of the vine uses light energy to create chemical energy and (ii) uses that energy to convert low-energy carbon into high-energy carbon compounds.  Photosynthesis is carried out in organelles (chloroplasts) which contain light-absorbing pigments called chlorophyll, the substance which gives the green color to leaves, stems, and inflorescences.  In the first step, chlorophyll absorbs photons and utilizes the captured energy to produce adenosine triphosphate (ATF), the chemical energy which is used by cells to power metabolic activity.
The second phase is light-independent and utilizes the energy and molecules from the first phase for carbon fixation and the production of photosynthates (sucrose, fructose, glucose, organic acids, proteins, fats, etc.).

Vine leaves, having the largest surface area, are the highest volume photosynthate producers.  The youngest (and most photosynthetically active) leaves can be found in the middle and upper parts of the shoot and on the laterals (Kuljancic et al.).

The photosynthates are either utilized immediately or warehoused for later use depending on the state of vine development.  Photosynthates are allocated to “sources” and “sinks” based on time of season and needs of the vine and are moved between these poles in a process called translocation.  Most of the photosynthates produced post-harvest are translocated to the roots and trunk to be stored as carbohydrates for next season’s vine growth.  According to Lebon et al., starch is the most important part of the sugar reserves for all grapevine varieties and, during winter dormancy, can be as much as 1/3 of the root’s dry weight. 

The analog for customers in the grapevine energy supply chain are the totality of cells with metabolic needs.  Net consumers of photosynthates are shoot tips, root tips, and developing fruit during the growing season and the woody parts of the vine post-harvest.  When soil temperature reaches 10-12 degrees centigrade, metabolism is activated and carbohydrates from the woody parts of the vine are mobilized to support annual growth.

Regardless of whether it is sourced from stored carbohydrates, or from photosynthates fresh off the assembly line, the energy within these foods are released by a process called aerobic respiration.  The process is driven by cell-resident organelles called mitochondria which generate chemical energy (ATP) by “metabolizing sugars, fats, and other chemical fuels with the assistance of molecular oxygen sourced from the atmosphere and the soil.” 
Respiration is a continuous process in which critical vinous products such as proteins, enzymes, colors, aromas, and flavors are produced.


In this post I mapped the grapevine energy supply chain to a generalized supply chain model.  In a follow-up post I will show how modern viticultural science can be viewed through supply chain management lens.

©Wine -- Mise en abyme

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