Definition - What does Node mean?
A node or “bud” is an enlarged spot on the shoot of a vine that will either grow a fruiting shoot or a leaf. The nodes can also grow tendrils (across from the leaf) which are responsible for supporting the vine and wrapping around trellis wires. Nodes can communicate many things about the vine to the viticulturist, so it important to monitor their growth and progression.
WineFrog explains Node
The nodes are thickened parts of tissue that are rich in nutrients and cell structures. They can form clusters or individual leaves, new shoots or tendrils – depending on the type of vine and pattern of growth. Each node can denote how fast the vine is growing by measuring the distance between them, which is called the internode. This internode length will vary throughout the growing season as the rates of development changes (increases or decreases). Viticulturists can monitor the internodes to determine how well the vine is growing and if it is healthy in comparison to other vine growth.
Every grapevine node system has a pattern that shows what type of tissue is going to grow out of which node. Nodes at the base of the shoot may grow clusters or growth shoots. Opposite of the clusters are leaf nodes, and tendrils can replace clusters but only on every other node. Nodes that are closer to the top grow shoots and leaves to enhance the canopy, and nodes in the middle typically grow more clusters for added vine support.