zinc is a micro element that plays an important role in the flowering and fruitset process. When zinc is immobile in the vine, symptoms first show up in the younger leaves.
When vines are deficient in zinc, the leaves begin to mottle and the petiolar sinus begins to widen with sharp teeth showing up on the leaf edges. Some shoots become stunted and zigzagged.
Zinc deficiency can become confused with herbicide damage from glyphosate and 2-4D.