Abstract
It has been believed in eggplants cultivation that the lusterless (Tsuyanashi) fruit is produced by the soil water shortage. But it seems that the reasoning has failed to satisfy all of the observations on the growth condition of eggplants at the farm.
In this study author examined the loss of luster or reddish brown coloring on the skin in relation to the growth factors, i.e. greenhouse temperature, soil moisture, plant training, and concentration of the fruiting regulator hormone.
The study highlighted the higher day and night greenhouse temperature as the major factor in the production of the lusterless fruits, and the soil moisture shortage was supporting the process. The following mutual interactions between the factors were also contributing to increase the lusterless fruits production, i.e. 1) temperature and soil moisture, 2) temperature and plant training, and 3) temperature, soil moisture and plant training. More amount of fruits lost luster by the longer aging on the fruit after the flowering. Furthermore the poor soil moisture and the lean concentration of the fruiting regulator hormone increased the size of lusterless area on a fruit.
On the other hand, the reddish brown coloring of the fruit was caused by the poor plant training which led over growth and luxuriant branch development of the plant.
