Often, the images that come to mind when we think of a grapevine are of twisting, flaky cocoa-colored vines, large, vibrant overlapping leaves, twisting tendrils and heavy hanging bunches of ripe grapes. But the anatomy of a grape is complex, made up of essential inner and out parts like the Phloem, which is responsible for transporting essential nutrients throughout the plant that were created by photosynthesis.
Grapevines produce over 65 million tons of incredible products such as; wines, jellies, juices and oil each year. All of these products come from a large family that consists of uncountable species, like Vitis Vinifera and Vitis Labrusca, and varietals, which each produce incredibly diverse fruits, however, the basic anatomy of the grapevine is the same from species to species. Here we will look at the basic anatomy, what each part of the vine is and what it is responsible for, from the roots below ground to top of the vine canopy.
The Roots of A Grapevine
The root of the vine is the delicate, intricate system of bare vine that grows underground. Literally, it is the foundation of a vine, the roots anchor the vine while absorbing and storing nutrients and hydration from the soil. New growth and young roots are made up of rapidly dividing cells, that are protected by a root cap, these cells allow the roots to extend and grow under the ground. As the roots grow, they transform from thin white roots, known as the epidermis, and become the hearty brown roots known as the exodermis, which protects cortex and endodermis and the Casparian strip. The Casparian strip not only regulates the uptake and transport of nutrients, much like they Xylem and Phloem up above, it also protects the vines from toxic compounds in the soil.
The Rootstock, A Vineyard's Crown Jewel
It’s important to differentiate the root of a grapevine from the rootstock. Often, the rootstock of a vine, is not of the same varietal as the vine, and the choice of rootstock determines how healthy the vine will be. The practice of grafting vines onto disease-resistant rootstock became popular in France after the Great French Wine Blight, when it was discovered that American rootstocks were resistant to phylloxera. Although it was the transport of these American Rootstocks that caused the blight in the first place, after almost 70% of the country's entire crops were lost to the disease carried by phylloxera, an aphid, there was no other option but to graft the American rootstocks to the French vines in order to create a more disease-resistant plant. Afterwards, the French vines grew vigorously on the American rootstock.
Today, the rootstock is chosen not only for its disease resistance, but also for the type of soil and climate in the growing region.
Vine Grafting, the Graft Union and the Scion
The grafting of rootstock leads us to discuss the Graft Union which is the location on the vine where the scion meets with the rootstock after the grafting procedure; the scion itself is the fruiting vine that is grafted to the rootstock.
Where All Stories Are Heard, the Grapevine
The rootstock and the scion together form the foundation of the vine. When the vine is dormant in winter, you can easily see the vine, because it is bare of fruit and leaves. The vine, like the roots and the rest of the structure are made up of cells and plant tissue that regulate growth and the transportation of nutrients. The 2 main types of plant tissue in the grapevine are meristematic and dermal cells.
Meristematic cells multiply along the vine which makes the vine grow, while dermal cells are found on the outermost layer of the vine and create a tough exterior that protects the vine from damage. The meristematic and dermal cells combined with other plant support the tissue make up the complete structure of the vine. The support cells, namely the outer layer, the collenchyma, which are thick and long, and the inner sclerenchyma which have fibers in the cell's walls, provide structure to the vine. The xylem plant tissue in the vine is responsible for transporting hydration and nutrients to the entire vine from the phloem, which is the tissue responsible for providing the food that is essential to the health and growth of the vine. The unique cellular structure of the vine allows the cells to move throughout the vine by transferring nutrients and hydration through perforated cell walls similar to the vascular system in humans and animals.
The Grapevine Trunk
The trunk of a vine can begin to look like the trunk of a small tree as it ages, it has a bark-like appearance, and as it ages, it gets thicker. The trunk is essentially the vine that grows vertically from the root ball out of the ground and continues until the vine begins to grow horizontally into cordons. When the vine splits and grows horizontally depends on how the vine is trellised or trained.
Cordons & Shoots
Cordons are the winding parts of the vine, usually a mature cane, that typically rests along a wire that runs perpendicular to the ground and trunk.
Shoots are the new growth of the vine in the spring. They start as little buds, then they grow like small green branches or "shoots". The shoots will bud leaves and will later bear the fruit of the vine; grape clusters. However, not all buds can become shoots, the axillary bud will appear at the stem close to shoots, but it will not grow; the vine keeps it in reserve, as a back-up. The axillary bud lies dormant if the vine has apical dominance, which helps the vine channel resources into the developing shoots, however, once the shoot is established or if it becomes damaged, the apical dominance will recede and the axillary bud will begin to grow.
The Canes & Tendrils of a Grapevine
Canes are the mature shoots that have born fruit and have become woody and browned after harvest at the end of the season. Most often, the canes are pruned, but some can be trained to be a part of the vine.
Grapevines are climbing plants, and the tendrils allow vines to pull themselves up to the light. Tendrils grow out of the shoots, and when they are young, they grow straight, however, as soon as they encounter a support, the tendril begins to wind around it in a process called circumnutation.
Grapevine Leaves and Fruit Clusters
Leaves are grown from the nodes off of the shoots. The nodes are areas of the shoots that are enlarged, and the distance between the nodes and leaves varies, due to the season and is an indicator of the growth rate of the vine. The leaves are integral to the vigor of the plant. During the lifetime of a leaf, they export more resources from photosynthesis than they use. Before senescence or leaf fall, photosynthates are stored in the root, and leaf minerals are transported back to the shoots, canes and trunk of the vine.
Clusters, are the much sought after fruit of the vine. Typically, grapes grow into a V-shaped cluster, however, different varietals have unique differences. When the grapes are young, they all appear green, however, when they ripen, depending on the varietal, they can be pale-yellow, red, deep purple or even blue-hued. These clusters are pressed and crushed in the beginning stages of the wine process in order to extract the juices needed to make wine.
The final anatomical item we'll cover is the canopy, which is comprised of the shoots, leaves and fruit that cover the vine, similar to the canopy of a forest, which is made up of the vegetative parts of trees and cover the forest ground.
The anatomy of a grapevine is important, because each varietal gains its characteristics from the make-up of their vines. We cover these terms extensively and want our readers to get to know these interesting details, and a good ole' guide to a grapevine's make-up does the trick.