viticulture Viticulture (, "vine-growing"), viniculture (, "wine-growing"), or winegrowing is the cultivation and harvesting of grapes. It is a branch of the science of horticulture. While the native territory of ''Vitis vinifera'', the common grape vine ...

, the canopy of a grapevine includes the parts of the vine visible aboveground - the trunk, cordon, stems,

leaves A leaf (: leaves) is a principal appendage of the stem of a vascular plant, usually borne laterally above ground and specialized for photosynthesis. Leaves are collectively called foliage, as in "autumn foliage", while the leaves, stem, ...

flowers Flowers, also known as blooms and blossoms, are the reproductive structures of flowering plants ( angiosperms). Typically, they are structured in four circular levels, called whorls, around the end of a stalk. These whorls include: calyx, m ...

, and

fruit In botany, a fruit is the seed-bearing structure in flowering plants (angiosperms) that is formed from the ovary after flowering. Fruits are the means by which angiosperms disseminate their seeds. Edible fruits in particular have long propaga ...

. The canopy plays a key role in light energy capture via

photosynthesis Photosynthesis ( ) is a system of biological processes by which photosynthetic organisms, such as most plants, algae, and cyanobacteria, convert light energy, typically from sunlight, into the chemical energy necessary to fuel their metabo ...

, water use as regulated by

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. It is a passive process that requires no energy expense by the plant. Transpiration also cools plants, c ...

, and

microclimate A microclimate (or micro-climate) is a local set of atmosphere of Earth, atmospheric conditions that differ from those in the surrounding areas, often slightly but sometimes substantially. The term may refer to areas as small as a few square m ...

of ripening grapes. Canopy management is an important aspect of viticulture due to its effect on grape yields, quality, vigor, and the prevention of grape diseases. Various viticulture problems, such as uneven grape ripening, sunburn, and frost damage, can be addressed by skillful canopy management.Weiss, S.B., D.C. Luth, and B. Guerra. 2003. Potential solar radiation in a VSP trellis at 38°N latitude. ''Practical Winery and Vineyard'' 25:16-27. In addition to pruning and leaf trim, the canopy is often trained on trellis systems to guide its growth and assist in access for ongoing management and harvest.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pp. 134-135 Oxford University Press 2006 .

Vine

The vine is the main part of the grapevine, extending from the

root system In mathematics, a root system is a configuration of vector space, vectors in a Euclidean space satisfying certain geometrical properties. The concept is fundamental in the theory of Lie groups and Lie algebras, especially the classification and ...

in the ground up to the cordons, or arms, of the vine. When the grape is young the trunk is very pliable and must be supported by stakes as part of a vine training system. The height of the trunk varies depending on

grape variety This list of grape varieties includes cultivated grapes, whether used for wine, or eating as a table grape, fresh or dried (raisin, Zante currant, currant, sultana (grape), sultana). For a complete list of all grape species, including those unimp ...

and the type of trellis system being used and can range from 4 inches (10 cm) to 30 feet (10 m). During winter

dormancy Dormancy is a period in an organism's Biological life cycle, life cycle when growth, development, and (in animals) physical activity are temporarily stopped. This minimizes metabolism, metabolic activity and therefore helps an organism to conserv ...

, the trunk can be vulnerable to extreme freezing conditions and will be sometimes buried and insulated with soil to protect it.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition, p. 714. Oxford University Press 2006 . The trunk is composed of sleeves of conductive tissue, most notably the

phloem Phloem (, ) is the living tissue in vascular plants that transports the soluble organic compounds made during photosynthesis and known as ''photosynthates'', in particular the sugar sucrose, to the rest of the plant. This transport process is ...

and

xylem Xylem is one of the two types of transport tissue (biology), tissue in vascular plants, the other being phloem; both of these are part of the vascular bundle. The basic function of the xylem is to transport water upward from the roots to parts o ...

. The outside bark of the vine contains the phloem tissues which transports sap, enriched by

sugar Sugar is the generic name for sweet-tasting, soluble carbohydrates, many of which are used in food. Simple sugars, also called monosaccharides, include glucose Glucose is a sugar with the Chemical formula#Molecular formula, molecul ...

s and other molecules, from the leaves to the rest of the vine. During the annual growth cycle of the grapevine, the vine will start to store

carbohydrate A carbohydrate () is a biomolecule composed of carbon (C), hydrogen (H), and oxygen (O) atoms. The typical hydrogen-to-oxygen atomic ratio is 2:1, analogous to that of water, and is represented by the empirical formula (where ''m'' and ''n'' ...

energy in the wood part of the trunk and roots. The downward passage of phloem sap to the roots and this storing process can be interrupted by the viticultural practice of "girdling" or cincturing the vine. This process can improve fruit set by forcing the vine to direct most of its energy towards developing the grape clusters. The xylem is the woody tissue on the inside of the trunk that moves sap, enriched with

water Water is an inorganic compound with the chemical formula . It is a transparent, tasteless, odorless, and Color of water, nearly colorless chemical substance. It is the main constituent of Earth's hydrosphere and the fluids of all known liv ...

mineral In geology and mineralogy, a mineral or mineral species is, broadly speaking, a solid substance with a fairly well-defined chemical composition and a specific crystal structure that occurs naturally in pure form.John P. Rafferty, ed. (2011): Mi ...

s and other compounds, up from the roots to the leaves.

Cordon

The cordon, or "arms", of the grapevine extend from the trunk and are the part where additional arms and eventually leaves and grape cluster cordons are usually found along wires as part of a trellis system. This training usually fixes the cordon into a permanent position, such as horizontal extending from the trunk in opposite directions.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition, p. 199. Cambridge University Press 2006 .

Stem

The terms stem, stalks and shoots are sometimes used interchangeably but viticulturalists generally make some differentiation. The stem of the grapevine item, extending from cordon, is considered the shoot and this part is most often pruned in the process of "shoot thinning" to control grape yields. The stalk extending out to hold the grape cluster is known as the bunchstem while the stem of the individual grape berry is the pedicel.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition, p. 663. Oxford University Press 2006 . The shoot of the vine develops from new buds located on the cordon and grow to include the leaves,

tendril In botany, a tendril is a specialized Plant stem, stem, leaf or Petiole (botany), petiole with a thread-like shape used by climbing plants for support and attachment, as well as cellular invasion by parasitic plants such as ''Cuscuta''. There ar ...

s and eventually grape clusters. Shoots first begin to appear in spring, following bud break, accelerating growth till the flowering stage and usually slowly by the time that the vine begins veraison. During the stage of veraison (typically mid to late summer), the shoot starts to harden and change color from green to brown.

Cane

The shoot is ripening at this point and becomes known as a "cane." In wintertime, the canes of the grapevine are usually completely cut off with the amount and weight of the cane being used to gauge the amount of pruning and canopy management that will be needed for the upcoming year. The "tip" of the shoot is the small (0.4 in/1 cm) part of the shoot furthermost from the vine. Viticulturalist use the growth of this tip as an indication of vine vigor because the tip competes with the grape clusters for resources from the vine. Ideally, shoot growth should come to a stop around the time of veraison; a vine that continues growing the shoots will stand the chance of less fully developed grape clusters.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition pp. 627-628 Oxford University Press 2006 .

Leaves

Chardonnay leaf with naked vein highlighted

A grapevine's leaves are the most visible part of the canopy and also one of the most important. It is through the leaves that the vital

physiological Physiology (; ) is the science, scientific study of function (biology), functions and mechanism (biology), mechanisms in a life, living system. As a branches of science, subdiscipline of biology, physiology focuses on how organisms, organ syst ...

process of

takes places which creates the carbohydrates that the vine needs to grow and process grape clusters. The size of the leaves vary due to grape varieties with varieties like Merlot having very large leaves and

Gewürztraminer Gewürztraminer () is an aromatic wine grape variety, used in white wines, and which performs best in cooler climates. In English, it is sometimes referred to colloquially as Gewürz ( ; although this is never the case in German, because mean ...

noted for having small leaves. The typical size is normally comparable to that of a human hand. In addition to size, there are many of other unique characteristics to the leaves that ampelographers use for plant identification. The size and shape of the leaf's sinus (the opening space where the blade of the leaf connects to the petiole), the shape of the "teeth" along the outer edge, the arrangement of the five lobes or projecting parts and the angle and length of the veins can all assist in identifying the grapevine.J. Robinson (ed) ''"The Oxford Companion to Wine"'' Third Edition, pp. 396-397. Oxford University Press 2006 . The color of the leaf can be an indication of the health and nutrition of the vine.

Chlorophyll Chlorophyll is any of several related green pigments found in cyanobacteria and in the chloroplasts of algae and plants. Its name is derived from the Greek words (, "pale green") and (, "leaf"). Chlorophyll allows plants to absorb energy ...

in the leaf gives it a natural greenish color. Prior to the winter dormancy, the vine will stop being photosynthetically active which will contribute to a natural break down of chlorophyll and changing of color. However, deficiency in

nitrogen Nitrogen is a chemical element; it has Symbol (chemistry), symbol N and atomic number 7. Nitrogen is a Nonmetal (chemistry), nonmetal and the lightest member of pnictogen, group 15 of the periodic table, often called the Pnictogen, pnictogens. ...

sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...

could cause the vine to turn prematurely (such as before

harvest Harvesting is the process of collecting plants, animals, or fish (as well as fungi) as food, especially the process of gathering mature crops, and "the harvest" also refers to the collected crops. Reaping is the cutting of grain or pulses fo ...

) yellow. The appearance of reddish spots of brown "dead zones" could be the sign of a viral infection (such as the leafroll virus) or contamination through the use of

herbicide Herbicides (, ), also commonly known as weed killers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page f ...

s. Viticulturalist will use a leaf to fruit ratio as a guideline in determining a vine's ability to fully ripen grapes. Quite different from the consideration of yields, the balance of leaf cover (needed for photosynthesis) and proportion of fruit (judged by weight rather than number of clusters) could have the most substantial effect on the quality of the grape for

winemaking Winemaking, wine-making, or vinification is the production of wine, starting with the selection of the fruit, its Ethanol fermentation, fermentation into alcohol, and the bottling of the finished liquid. The history of wine-making stretches over ...

. Pioneered by viticulturalist Richard Smart, the idea of maintaining a "balanced vine" is to have just enough leaf cover for the plant to produce the energy needed to ripen the grape without having too much photosynthetic activity to where the vines has a surplus of energy and continues growing more shoots. Additionally, leaves provide shade to the grape clusters which be beneficial in protecting the clusters from the harshness of heat stress ("sunburn") but excessive shade can also decrease the development of

anthocyanin Anthocyanins (), also called anthocyans, are solubility, water-soluble vacuole, vacuolar pigments that, depending on their pH, may appear red, purple, blue, or black. In 1835, the German pharmacist Ludwig Clamor Marquart named a chemical compou ...

s and other phenolics and other important compounds in the grape. Many vineyards employ the practice of leaf removal throughout the growing season to try to maintain optimal leaf coverage.

References