The possibilities of climatic regulation take an important place in contemporary studies on optimal greenhouse production.
The following climatic factors are of paramount importance in the greenhouse: light, temperature, carbon dioxide, air humidity and air circulation.
Light is the core of these studies.
The production of artificial light is not possible or hardly possible on account of economic considerations.
That is why greenhouse climate is so regulated as to allow optimal use of natural light.
The possibilities of regulating greenhouse phytoclimate are as follows heating, ventilation, carbon dioxide, roof sprinkling and shading.
This regulation apparatus cannot be used continually.
Two periods are noted in greenhouse climate regulation, viz.: 1) when ventilation is not or hardly needed to limit the maximal air temperature, and 2) when limiting the maximal temperature takes a central place.
During this period the possibilities of controlling the remaining climatic factors are very meagre.
This elaboration of the question focuses attention on raising tomato seedlings in the winter and on the possibility to control the various climatic factors.