Of tropical origin (Latin America) tomato has specific temperature requirements It is also the determining factor in the conduct of its culture. The tomato reacts to temperature variations that take place during its growth cycle. To give some examples, this affects the germination of seeds, the growth of sowing, flowering, fruit stake as well as the quality of fruit.

Indeed the low temperatures (less than 10 °) slow down or stop growth, lead to a shortening of the intersects and the formation of significant foliage to the detriment of fruiting. Above 17 ° the pollen germinates badly, the bouquets branch and the noueison is delicate. Conversely, high temperatures promote growth to the detriment of the inflorescence that can abort; A persistent dry and warm weather can cause abnormal lengthening of the pistil thus making a delicate self -pollination. Above 30 ° it is lycopene, pigment responsible for coloring tomatoes, which is no longer formed.

It is therefore the factor whose role is the most complex on the balance sheets/ fruit balance, that is to say the ratio of vegetative/ generative activity. You should know that the essential rule is as follows: it is the average daily temperature that influences the biological development of the tomato plan. In parallel we must keep in mind that it is the state of the plant that will determine this vegetative/generative relationship.

Vegetative character: Promotes growth of the plant, that is to say a plant with a lot of leaves (developed leaf surface) of tissues rich in light green water. Regular flowering but the flowers are pale yellow with the welded petals.

Generative character: unlike the vegetative character, the plant will be more stocky, dark green, purplish at the top of the rod. The flowering is good and the flowers are of an intense yellow, more capable of fruiting.

Vigor: it has no direct relationship with one or the other of these two characters, one can have a plant with a vegetative character to have a strong vigor and vice versa. Within the limits of etiolation we will promote vigor.

The higher this temperature, the greater growth (photosynthesis, perspiration). When the plant is devoid of fruit (before the 1st Nouaison), the more we heat, the more we activate vegetative development (growth of roots, stems, leaves). Conversely when the plant bears fruit, the more we heat, the more we promote their development and this at the expense of the leaves, so vigor decreases.

The higher the gap between day and night, the more generative the plant will be. Conversely, a spreading temperature does not stress the plant and promotes vegetative. In the nursery one only creates this gap at the time of the formation of the first bouquet in order to promote fruiting and it is reduced as we want to restore vigor to the plant.

In nursery, at the time of the release of the first bouquet, this difference is artificially created often over 4 periods per day by accentuating the speed of passage from a high temperature to a drop (temperature kick), so the stress caused plant is more important and creates a certain "generative effect".

For sowing, after lifting, you have to lower the night temperature around 15 ° or even 12 ° and when the plants are five weeks old that they are the size of a pencil you can still lower the temperature to 10 °; This thermal shock will have the effect of accentuating the generative character of the plant which will be more stocky, with dark green leaves, and therefore more capable of supporting a next transplantation.

It is obvious that thermal regulation is generally manage, in general, until the stage of implementation, in fact once in the ground it will be much more delicate, if not impossible to domesticate thermal variations. Only greenhouse or tunnel culture could allow it, but that at the expense of the flavor of the tomato; It is of public notoriety that a tomato at the top has much more taste than a greenhouse tomato often tasteless or even acid.