ACTION DE LA QUANTITÉ JOURNALIÈRE DE LUMIÈRE SUR LA FLORAISON, LE POIDS SEC ET LA TENEUR EN EAU DE QUELQUES PLANTES DE JOURS COURTS ET DE JOURS LONGS

Abstract— Experiments were carried on in the Liège Phytotron for two years to discover what reactions could be obtained when both short-day and long-day plants were placed in the same light energy per day (light intensity × daily light duration in various combinations) and receiving respectively 8 or 16 hr light per day. It was observed that both types of plants give parallel dry weight curves in both long-day and short-day, but this happens only during the vegetative state following germination.
Differences occur in those dry weight curves in short-day plants and also in long-day plants when cultivated under inductive photoperiodic light and induced to flower.
In these suitable light conditions, their dry weight increased compared with that of plants left in a non-inductive photoperiodic fight.
The evolution of tissue water content (stems, leaves, flowers), expressed as water % of the dry weight, is also interesting to observe in the same experimental environments. This evolution plays an important physiological part in flower formation, as has been shown before by R. Bouillenne.
Both types of plants cultivated in their respective non-inductive light point out a very simple curve of water content. First a rapid increase of water into the tissues during the first 10 days after germination; then from this maximum, the curve goes down regularly and slowly till a constant low level.
However, in inductive light exposure, water content percentage curves are really different for both types of species. Considering the same daily value of light energy given in each case, it is possible to conclude that the induction of flower does not depend on the daily light quantity but on something else which is connected with the photoperiodism.
These fluctuations of the water content will be investigated.