Conditions Influencing Inflorescence Differentiation

In reviewing my blogposts that I posted in 2016, I realized that I had not completed the discussion I began on June 17, 2016 regarding understanding Grapevine Inflorescence, so I hope to continue today. I must confess that in looking through my photos, I absolutely love spring and budbreak and the pink and greens that young buds bring to the vineyard.
I have written about my initial inability to grasp The Mysterious Life of Grape Buds and delved into inflorescence formation in two subsequent postings that were rather technical and complex in Grapevine Inflorescence Formation---Parts 1 and 2 and Inflorescence Formation Part 3.
Although Mother Nature has the upper hand in inflorescence induction, it is important to understand the conditions that lead to fruitfulness that occur in the spring and summer of the previous year¹:

• The induction of inflorescence differentiation generally coincides with blooming and the slowing of vegetative growth.
• Induction is particularly sensitive to water stress, and its occurrence during blooming can severely reduce bud fruitfulness.
• Induction usually occurs about 2 weeks before morphological signs of differentiation become evident.
• A period of several weeks may separate the initiation of the first and second inflorescence primordia (anlagen). This period tends to correspond to growth stages 13 to 18 of the Eichhorn and Lorenz (E–L) system.
• Warm conditions (77–95 ^oF) promote cytokinin synthesis, which favors inflorescence differentiation.
• Cool conditions favor gibberellin synthesis, which promotes vegetative growth and limits nutrient accumulation.
• Optimal nitrogen, potassium, and phosphorus supplies also promote the synthesis and translocation of cytokinins from the roots.
• Factors such as high vigor, defoliation, or untimely drought, which disrupt carbohydrate accumulation, can interfere with inflorescence initiation.
• By midsummer, when branch initials have developed, the anlagen (primordia) become dormant.
• Differentiation recommences in the spring when the buds begin to swell and individual flowers form.
• Sun exposure is generally more important than day length in inducing fruit-bud development in vinifera cultivars.
• Fruitfulness is primarily associated with the primary bud. The fruitfulness of secondary buds is generally important only if the primary bud dies.

Reference:
1. Ronald Jackson, Wine Science Third Edition, Elsevier, 2008, pg. 68.