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Growing of vegetables, roots and tubers

Vegetable farming is the growing of vegetables for human consumption. Traditionally it was done in the soil in small rows or blocks, often primarily for consumption on the farm, with the excess sold in nearby towns. Later, farms on the edge of large communities could specialize in vegetable production, with the short distance allowing the farmer to get his produce to market while still fresh. The three sisters method used by Native Americans(specifically the Haudenosaunee/Iroquois) grew squash, beans and corn together so that the plants enhanced each others growth. Planting in long rows allows machinery to cultivate the fields, increasing efficiency and output; however, the diversity of vegetable crops requires a number of techniques to be used to optimize the growth of each type of plant. Some farms, therefore, specialize in one vegetable; others grow a large variety. Due to the needs to market vegetables while fresh, vegetable gardening has high labor demands. Some farms avoid this by running u-pick operations where the customers pick their own produce. The development of ripening technologies and refrigeration has reduced the problems with getting produce to market in good condition.
Roots : In vascular plants, the root is the organ of a plant that typically lies below the surface of the soil. This is not always the case, however, since a root can also be aerial (growing above the ground) or aerating (growing up above the ground or especially above water). Furthermore, a stem normally occurring below ground is not exceptional either (see rhizome). So, it is better to define root as a part of a plant body that bears no leaves, and therefore also lacks nodes. There are also important internal structural differences between stems and roots.

.Tubers are various types of modified plant structures that are enlarged to store nutrients. They are used by plants to survive the winter or dry months and provide energy and nutrients for regrowth during the next growing season and they are a means of asexual reproduction. Two different groups of tubers are: stem tubers, and root tubers.

A stem tuber forms from thickened rhizomes or stolons. The tops or sides of the tuber produce shoots that grow into typical stems and leaves and the under sides produce roots. They tend to form at the sides of the parent plant and are most often located near the soil surface. The below-ground stem tuber is normally a short-lived storage and regenerative organ developing from a shoot that branches off a mature plant. The offspring or new tubers, are attached to a parent tuber or form at the end of a hypogeogenous rhizome. In the fall the plant dies except for the new offspring stem tubers which have one dominant bud, which in spring regrows a new shoot producing stems and leaves, in summer the tubers decay and new tubers begin to grow. Some plants also form smaller tubers and/or tubercules which act like seeds, producing small plants that resemble (in morphology and size) seedlings. Some stem tubers are long lived such as those of tuberous begonia but many tuberous plants have tubers that survive only until the plants have fully leafed out, at which point the tuber is reduced to a shriveled up husk.
Stem tubers generally start off as enlargements of the hypocotyl section of a seedling but also sometimes include the first node or two of the epicotyl and the upper section of the root. The stem tuber has a vertical orientation with one or a few vegetative buds on the top and fibrous roots produced on the bottom from a basal section, typically the stem tuber has an oblong rounded shape.
Tuberous begonia and Cyclamen are commonly grown stem tubers. Mignonette vine (Anredera cordifolia) produces aerial stem tubers on 12-to-25-foot-tall (3.7 to 7.6 m) vines, the tubers fall to the ground and grow. Plectranthus esculentus of the mint family Lamiaceae, produces tuberous under ground organs from the base of the stem, weighing up to 1.8 kg per tuber, forming from axillary buds producing short stolons that grow into tubers.Potatoes
Potatoes are stem tubers, which are the development of enlarged stolons thickened into a storage organ.
The tuber has all the parts of a normal stem, including nodes and internodes, the nodes are the eyes and each has a leaf scar. The nodes or eyes are arranged around the tuber in a spiral fashion beginning on the end opposite the attachment point to the stolon. The terminal bud is produced at the farthest point away from the stolon attachment and tuber thus shows the same apical dominance of a normal stem. Internally a tuber is filled with starch stored in enlarged parenchyma like cells; also internally the tuber has the typical cell structures of any stem, including a pith, vascular zones and a cortex.
The tuber is produced in one growing season and used to perennialize the plant and as a means of propagation. When fall comes the above ground structure of the plant dies and the tubers over winter under ground until spring, when they regenerate new shoots which use the stored food in the tuber to grow. As the main shoot develops from the tuber, the base of the shoot close to the tuber produces adventitious roots and lateral buds on the shoot, The shoot also produce stolons that are long etiolated stems. The stolon elongates during long days with the presence of auxins and high jabubu levels that prevent root growth off of the stolon. Before new tuber formation begins the stolon must be a certain age. The hormone lipoxygenase is involved in the control of potato tuber development.
The stolons are easily recognized when potato plants are grown from seed, as the plants grow, stolons are produced around the soil surface from the nodes. The tubers form close to the soil surface and sometimes even on top of the ground. When potatoes are cultivated, the tubers are cut into pieces and planted much deeper into the soil. By planting the pieces deeper there is more area for the plants to generate the tubers and their size increases. The pieces sprout shoots that grow to the surface, these shoots are rhizome like and generate short stolons from the nodes while in the ground. When the shoots reach the soil surface they produce roots and shoots that grow into the green plant.
Root tubers
A tuberous root or storage root, is a modified lateral root, enlarged to function as a storage organ. The enlarged area of the root-tuber, or storage root, can be produced at the end, or middle of a root, or involve the entire root. It is thus different in origin but similar in function and appearance to a stem tuber. Examples of plants with notable tuberous roots include the sweet potato, cassava, Yam and Dahlia.
Root tubers are used to perennialize the plant, they store nutrients over periods when the plant can not actively grow, thus permitting survival from one year to the next. The thickened roots are storage organs that differ from stem tubers. The massive enlargement of secondary roots typically represented by Sweet Potato (Ipomoea batatas), have the internal and external cell and tissue structures of a normal root, they produce adventitious roots and stems which again produce adventitious roots.

 
Freshly dug sweet potato plants with tubers

From Wikipedia, the free encyclopedia : Growing of vegetables, roots and tubers