Question

In potato tuberizatiob does not occur at a tekperature above

Answer 1

The reason that potato plants form tubers, or the process of tuberization, has long puzzled both farmers and scientists. After all, related species such as the tomatoes do not form tubers. Of course we can say that potato contains the genes both to form the tubers and to regulate when these tubers form, but that begs the question as to the exact nature of the controls on the process. We know that tuberization is a regulated process, and in the wild relatives of potatoes and in some cultivars this is regulated by the length of day, or photoperiod. Thus tuberization occurs under short day lengths, and is also promoted by low night temperatures as would occur in the fall, because in nature the tuber is the plant's way of surviving from season to season. In most commercial varieties, this propensity to tuberize only in short days has largely been selected out, so that tuber formation takes place even under the long days of midsummer. From a scientist's point of view, however, this regulation of tuberization by short days in andigena-type potatoes provides a useful switch to ask what internal signals cause potatoes to produce tubers when at other times they do not. Most research on tuberization is done on such photoperiod-sensitive potatoes.

The first thing we need to note is that tuberization is not under the control of a single signal. When a large population of offspring from crosses of potatoes of differing genetic makeup, and degree or time of tuberization were analyzed genetically by Jan van den Berg, together with Elmer Ewing, it was found that tuberization was regulated by 12 locations on eight of the 12 chromosomes in potatoes, and if all six of the alleles (form of genes) favoring tuberization were present they could account for 98 percent of the promotion of tuberization. Thus tuberization is under the control of several genes, indicating the likelihood that tuberization is regulated by a balance of several factors.