Articles
INFLUENCE OF GROWTH REGULATORS ON FRUIT DEVELOPMENT
Treatment with Alar and PP333 in spring reduces the size of fruit.
With the variety ‘Gravenstein’ we have observed that PP333 has the effect of significantly diminishing the fruit size, but it enhances bitter pit.
Fruit treated with Alar had the better skin color at harvest time than those treated with PP333, which showed a high percentage of green fruit.
PP333 produced stronger inhibition of shoot growth than Alar.
However this regulator seems to be very persistent in the soil.
One year after uprooting the experimental trees we observed a phytotoxic effect on a consecutive radish culture.
We found reduced fruit drop in June on AVG treated ‘Jonathan’ trees.
The fruit load was much higher but the fruit size was strongly reduced.
The positive effect was the reduction of internal breakdown.
While application of GA3, with or without addition of Benzyladenin, improved fruit set in ‘Conference’ pears, no significant results could be observed in the ‘Comice’ variety.
The length/diameter ratio of GA3 treated ‘Conference’ pears differs significantly from the ratio of pears with normal seeds, but no difference was observed compared with untreated but seedless fruits, thus the change of shape seems to be a consequence of the absence of seeds.
In an experiment with quince, GA3 improved the fruit set, but one effect was deformation of fruit shape.
In another experiment with pears we found that some growth regulators were able to enhance fruit set after flowering.
With the ‘Conference’ Promalin and AVG treatment showed good results, but only the AVG treatment reduced fruit abcission in June and caused better fruit set after this period in ‘Comice’.