THE USE OF AUXIN SPRAYS OR ARTIFICIAL POLLINATION IN ORDER TO IMPROVE FRUIT-SETTING OF TOMATOES GROWN UNDER GLASS
Since the effects of auxin sprays and artificial pollination on fruit-setting and the early and total yield of tomatoes are known very well, it seems sufficient to present our data on these phenomena in outline only, so that the main purpose of this paper could be a discussion in more detail of the influence of these treatments, as well as the influence of the environmental conditions, on fruit quality.
Auxin sprays. The -napthtoxyacetic acid in concentration 25 to 50 ppm (depending on the light intensity) and Polish preparation "Betokson" (containing alcoholic solution of this acid with an addition of a wetting agent) were found to be the best chemicals, since they gave satisfactory results upon fruit-setting, and were not so risky in use as other, more active substances, like 2,4-D or 2,4,5-T. Spraying the inflorescences only, with large amounts of the solution, or dipping them into auxin solution was better, than spraying the whole plant.
In our experiments, double treatment of each inflorescence gave better results than the single one (the first spraying, when the one half of the flowers in the truss were fully opened, and the second one, when the remaining flowers had opened; that means - every 4 – 5 days). Spraying with the auxins only the first inflorescence on the plant, resulted in a higher early crop than spraying all inflorescences on the whole plant, because of very strong competition between the developing fruits.
Artificial pollination. The effects of artificial pollination depended strongly on the method used (graph E). Using the poorer method of pollination (hand shaking of the plants) one should repeat the treatment every day, while with better methods (electric truss-vibrator) only twice a week.
The results of another experiment, presented in table 1, show that the pollination in noon-day hours was the most effective.
The two methods of improving fruitsetting, mentioned above, namely: auxin sprays and artificial pollination were compared in one experiment, the data of which are given in table 2. There are no significant differences (besides few exceptions) in the effectiveness of these two methods, however, the combined method (auxin spraying and pollination) seems to be better than the others and hand shaking of the plants a little worse, than auxin sprays. In some cases, when the natural fruit-setting is limited by poor fertilization (i.e. in the case of too low temperature), auxin sprays could be more effective than artificial pollination. There are some cases, on the other hand, where auxin sprays are very ineffective, i.e. in the conditions of very low light intensity (in winter), or if too many fruits in the truss are set already.
The effects of the auxin sprays or artificial pollination on the fruit quality. There are the following drawbacks imputed to the auxin treatment; reduced colour quality of the fruits, softening of the fruits, susceptibility to bruising and cracking, deformations in the shape of the fruits, hollow locules, "puffy" fruits, abnormally green colour of gelatinous pulp. But all of these phenomena may also occur without any application