One of the very significant and fundamental issues in the phasic theory is the question of reversibility of phasic changes , i. e. the question of re

Reversibility of phasic changes in plants [development]

One of the very significant and fundamental issues in the phasic theory is the question of reversibility of phasic changes, i. e. the question of reversibility of plant development.

Approaching the issue theoretically, we can assume that the development cannot go back, and can only be forward moving, which follows directly from the principles of materialist dialectics. At the same time, the literature describes numerous cases of reversibility, when, for example, flower sprout under the influence of certain conditions gives the formation of vegetative organs — the leaves. Numerous experiments on “devernalization” are also described. Assessing all relevant facts described in the literature, we can divide them into a number of cases:

  • Seed vernalization obviously passed in abnormal environmental conditions, such as in nitrogen atmosphere. Phasic changes in these conditions just did not occur.
  • When vernalized seeds are too overexposured, their growth points die, and the newly regenerated growth points do not have phasic changes, and it is clear that in this case the plant won’t bloom.
  • The third case is related to the fact that phasic changes passed, but there are no suitable conditions for their manifestation.

For example, it happens that even the flowering shoots in testes of the biennial crops, upon the occurrence of a high temperature and, especially in the short-day conditions, gradually stop flowering. The leaves thicken, leaf blade extends, and apparently they do not differ from the leaves of plants in the first year of life. Different varieties of cabbage begin to form a large number of small heads.

Externally, these vegetative organs resemble their respective organs of plants in the first year of life and cause a wrong conclusion if there is a “reverse” the plant development. However, these plants are very different from the plants in the first year of life according to their willingness to bloom. As soon as the required conditions are created, “vegetative” organs on these flowering shoots begin to bloom very quickly, while the plants in the first year do not bloom under the same conditions.

Many cases of the reversibility are related to that the vernalization phase consists of two processes. The first process involves the formation of the nutrients that the plant needs for phasic changes flow. This process has like a preparatory character. The second process is the assimilation of plant tissues the nutrients that were formed earlier under the influence of relevant environmental conditions. This process is already a genuine vernalization. The first process, bearing a preparatory character, is reversible, since the formed compounds (nutrients) can be destroyed; the second, in which has already begun a genuine process of development, is irreversible. Taken from

The corresponding tests have shown that the usual terms of vernalization for winter wheat (40-45 days) are insufficient. During this time, the process of vernalization does not manage to occur, and full completion of the vernalization phase occurs only in field conditions at low spring temperatures from +5 to 8-10 °C. If such unvernalizated seeds are exposed to elevated temperatures (30-33 °C), the plants won’t ear, as formed nutrients, that are required for vernalization phase, thus are destroyed or transformed into a form unfitted for vernalization process occurrence.

Thus, the influence of increased temperature causes no reversibility of the vernalization process, but only modification or destruction of those forms of nutrients, without which vernalization process does not occur.