If the small fruit varieties (SFV) of green pepper are cultivated in the greenhouse at night temperature 18°C, which is the optimum night temperature for the large fruit variety (LFV) at forced cultivation through winter, the SFV tend to bear unmarketable seedless and dwarf fruits. The SFV are cultivated at night temperature 23°C in commercial production.
One of the differences in flowering behavior between the SFV and the LFV at night temperature 18°C was related to the delay in anther dehiscence of the SFV on the day of flowering. If cultivated at 18°C, the LFV started to dehisce in the morning corresponding to the flowering. However, the SFV delayed dehiscence up until late in the afternoon and many flowers did not complete dehiscence by 4 p.m.. Furthermore, pollen shedding of the SFV was less in amount as compared to the LFV. Accordingly, the aging of pollen and pistils was considered as a possible cause of a low degree of fertilization.
According to the experiment conducted in a winter season on the aging of pollen and pistils, interference in fertilization for the above reason was denied, because pistils and pollen maintained their viability for two days and three days after flowering. However, the germination rate of pollen for 24 hours, on nutrient medium placed in the greenhouse, was low at average 11.8% on the day of flowering and the sterile rate of pollen reached 50% at 0 p.m. on the day of flowering. Thus in case of natural pollination, not only the smaller amount of pollen delivered to the stigma but also the poorer viability of pollen seemed to cause the higher rate of unsuccessful fertilization.
For commercial cultivation of the SFV peppers at lower temperature, it is necessary to increase the amount of pollen used on the flowering day, in order to improve fertility of the SFV. Since fertility of the SFV was improved by artificial pollination from the pollen of the SFV or LFV, the entomophilous method such as pollination by honey bees might be applied in a greenhouse, and interplanting of the LFV might further improve productivity of the SFV.