Flowers

Generally, grape vines produce extraneous shoots (“suckers”) on the plant in addition to those growing beyond the few desired on the cordon wanted for proper vine growth. Generally, again, suckers are less fertile than the primary shoots, they crowd the canopy of the vine, and their growth utilizes resources required for proper growth of the primary shoots. Further, the chaotic growth makes it difficult to manage the harvest. A crowded canopy (as will be discussed subsequently) is not a healthy one for grape growth. As shown in Figures 12.1 and 12.2 and noted earlier, buds (the small part of the vine that lies between the vine’s stem and the leaf stem or petiole) can start alongside the beginning of leaves at the base of the apical meristem. The buds swell and eventually produce shoots. As the shoot grows the flowers appear on a stem from the node, from where leaves have also sprung. That is, grape nodes hold buds that grow into leaves and inflorescences or “clusters of flowers” (i.e., the reproductive portion of a plant) arranged on a smaller stem growing from the node. It is not yet clear, despite recognizing the flow of nutrients and auxins as well as changes in proteins, how, after vernalization (i.e., the ability to flower so that fruit can be set—but only after exposure cold), the plant decides which, leaf or stem bearing flowers, should sprout from the node. The fundamentals of the coming forth of the buds are often outlined as a three-step process. First there is the formation of uncommitted primordia (primordia refer to tissues in their earliest recognizable stages of development) called “anlagen” (from German, in English, “assets” or “facilities”) at the apices of lateral buds. Second, differentiation of anlagen to form inflorescence primordia or tendril primordia occurs. Finally, flowers form from the inflorescence primordia when activated by phytohormones, nutrients, and growth regulators and when the external conditions of light and temperature are correct.