Grape Berry Circulatory System

One of my favorite articles that I refer to again and again, is called Understanding berry development which appeared in the July 2002 issue of Practical Winery and Vineyard. In that article, I thought that it was the phloem that shutdown as véraison approached, but I was wrong, it was the xylem! So much for my memory.
Here is an illustration from the article that shows how the grape berry changes in metabolites, size, as well as xylem and phloem activities.

Very little information is given in the 2002 article for the reason why the xylem appears to shut down once véraison occurs.
I came across an article published in March, 2018 in Wines & Vines that addressed the situation regarding the apparent cessation of xylem activity to the berry when véraison approaches.
The xylem and the phloem are part of the circulatory system of the grape berry. The xylem, shown in blue in the above diagram, is the main pipeline that delivers water, mineral nutrients, and growth regulators from the root system to the rest of the vine, including the developing grape berry. Water can move in and out of the berry through the xylem.
The phloem, shown in pink, is the vascular pathway that brings the photosynthates or the sugary solution made from photosynthesis by the leaf (the source), into the berry (the sink). The phloem can transport the photosynthates only one way, from the leaves to the berries.
The diagram also shows that after véraison, the xylem plays very little role in bringing nutrients and water to the ripening berry. Why is that?
The authors of the second article, Zhang and Hansen, set out to answer that question. They discovered that the xylem doesn't actually shutdown, but it is the phloem that takes over the sugar water importation as the berry begins to ripen.
The xylem is still functional after véraison, however, at this point, it is not supplying water to the berry. The authors make a case that late season drip irrigation will not dilute the sugars in the berry, helps to avoid water stress before harvest and helps to keep the vines healthy as they enter dormancy.
References:
1. Kennedy, James, Understanding berry development, Practical Winery and Vineyard, 2002, 24.
2. Yun Zhang and Melissa Hansen, Grapes and Irrigation Myths Debunked, Wines & Vines, March, 2018.