Vegetative Anatomy of Cultivated Grapes--A Review

Abstract

The anatomy of vegetative structures of cultivated grapevines, as described in selected literature, is presented, with emphasis on development of established vines of <i>Vitis vinifera</i>. Other topics briefly considered are the anatomy of propagules, muscadine grapes, tetraploid vines, phylloxera galls, mineral-deficient vines, and injury of leaves by ozone and 2,4-D. The terms used to describe grapevine morphology and anatomy are defined in a glossary. A growing root shows zones of cell division, cell elongation, and tissue differentiation. Vascular structure is similar in the root and the stem, although the mitotic activity of vascular and cork cambia is more irregular. Root cortex is often invaded by endotrophic mycorrhiza. The stem primary vascular system is composed of leaf, bud, and tendril traces. Procambium and phloem differentiate acropetally, and xylem differentiates in both directions from the nodes. During the first growing season of the stem, a cambium produces secondary xylem and phloem and extends rays. Xylem consists of large scalariform vessels surrounded by thick-walled pitted parenchyma and large masses of living septate fibers. Phloem consists of blocks of living septate fibers alternating with blocks of sieve elements, companion cells, and parenchyma. Ray cells are pitted and thick-walled in the xylem but thin-walled in the phloem. Cells of the stem and root store starch, which is greatly depleted when shoots begin to grow in the spring. Phellogen forms from the living cells of the nonconducting primary phloem in the first year in stems of <i>Euvitis</i> Planch. (in the subepidermal layer in <i>Muscadinia</i> Planch.), and then successively each year in the nonconducting secondary phloem. It cuts off all the tissues lying outside of it, and these are shed with the periderm. In spring, sieve elements formed the previous year are revitalized and function as conduits until new sieve elements are formed from the cambium. Each foliage leaf on a growing shoot has a precocious axillary bud consisting of a single prophyll and a variable number of leaves. This develops into the summer lateral branch. The four vascular traces of this axillary bud diverge from the traces of the subjacent tendril or bud, not from those of the subtending leaf. The bud in the prophyll of the summer lateral develops into the primary bud with 2-3 prophylls, a few leaves, and then several leaves opposed by clusters or tendrils in a generally regular pattern. Formed in the axils of the two basal prophylls of the primary shoot are the secondary and tertiary buds, respectively. These three buds, surrounded by the prophyll of the summer lateral, enter dormancy at the end of the growing season and constitute the compound bud or eye of the mature cane. The next season the primary bud develops into the fruiting shoot. The secondary and tertiary buds may develop into shoots or remain latent for extended periods. A tendril arises as a primordium on the apical meristem opposite that of a leaf. Two of its vascular traces are connected with those of the bud below it, and two with those of the leaf above it. It functions first as a hydathode and later as a twining organ. At each node, five traces to the leaf leave the ring of stem vascular bundles through separate gaps. The traces divide and anastomose to form the complicated network of palmate venation in the leaf, each tooth ending in a hydathode. Blade tissues of a mature leaf, which are differentiated from six layers of meristematic cells, comprise the upper epidermis, one layer of palisade cells, three layers of spongy mesophyll cells, and the lower epidermis with stomates.