Grapevine from Seed
Grapevine from Seed
It is widely claimed that growing the vines that will produce good wine grapes starting from seed is difficult. In part, as noted above, this is apparently due to the presence of different alleles expressed differently as a function of environmental factors. As a consequence, most wine is produced from grapes arising from a graft of a vine that already produces desirable product. However, it is possible to plant seeds to generate vines— although the product is not always what is expected! The fact that parent varieties (the flower of one parent and pollen of another) will generally produce a variety different from either parent is generally sought to be avoided in com¬mercial enterprise. However, since grape flowers (as will be discussed in Chapter 12) are often found as tight clusters, hermaphroditic reproduction either naturally or by intervention can be effective. Adventures in crossing, such as with the Vitis vinifera varieties Cabernet franc and Sauvignon blanc can be profitable. They are reported to have led to the formation of Cabernet Sauvignon. The grape seed needs to germinate. Germination is evidenced by the forming of the plant within the seed and the opening of the seed coat to produce a seedling (Figure 2.1). The plant embryo responds, as dictated by the genome, to the warmth of the soil and the availability of water, and continues to grow from the first cell division until the plant sprouts. It is not uncommon for seeds of many species to have set a genetically dictated timer. The setting of the timer may, for example, require that the ground be frozen and subsequently thawed (a process called vernalization). Once moistened, by a thaw or rain, the dry seed takes up water that passes through channels in cell walls and membranes (the inside of the cell being drier than the outside) that apparently open in response to the “timer” and in response to soil constituents. Ions found in the soil are washed in with the water. The water and nutrients in the soil are now available to put the enzymes and their cofactors, previously lying fallow in the seed, to work.
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