ミョウガの花粉発芽および花柱内花粉管伸長に及ぼす温度および相対湿度の影響

Abstract

Zingiber mioga Roscoe (2n=55) is a condimental vegetable originating in Japan. Cross breeding of this crop is difficult because of its low seed fertility. To investigate the cause of this low seed fertility, the effects of temperature, relative humidity (RH) and growth season on pollen germination and pollen tube growth in the style were examined in a laboratory.The optimum temperature for pollen germination in vitro ranged from 10 to 15°C, but the pollen tubes in the styles incubated at 20 or 25°C grew faster than in those incubated at 15 or 30°C.The percentage of pollen germination, the penetration into styles and the growth rate of pollen tubes increased as the relative humidity was elevated, and the best humidity for pollen longevity and pollen tube growth was at RH 100%. However, pollens which were stored at RH 60 or 80% for a few hours did not recover to the previous level of germinability, even by exposure to RH 100% prior to inoculation on the medium. Moreover, when spikes were exposed to RH 60% for 3 hours and pollinated with fresh pollen, pollen tube growth was also significantly inhibited.A high pollen fertility and a good pollen tube growth were observed in the growth season of January. Pollen fertility in June was as high as in January, while pollen tube growth in June was poor. On the other hand, in the hot summer of August and September, abortive pollen grains of small size increased and pollen tube growth diminished.From these results, we conclude that a favorable temperature and humidity for pollen activity and pistil receptibility may be in a range from 20 to 25°C and at RH 100%. In addition to these factors, it is also important for pollen activity that plants grow under cool conditions.