Pumpkin Fruit Growth
(Curcurbita spp.)

Most plants grow faster in the evening and at night than they do during the day. The same holds for pumpkins. In recent years, research on circadian rhythms in plants has shown that the night-time growth spurts of plants is under control of the plants biological clock. In this movie of pumpkins growing, these growth spurts are easily observed. It almost appears as though someone is at the end of the vine blowing up the pumpkins at night as if they are balloons and taking the next breath during the day. Plants can use the products of the days photosynthesis at night to aid in the uptake up water into their cells, which increases the turgor pressure of the cells and drives their enlargement. In the case of the pumpkins shown here, the enlargement of the cells in the fruit resuts in enlargment of the fruit.

Pumpkins are a warm-weather crop. Upon flowering, they initially produce male but eventually begin to produce both male and female flowers. The petals of each flower last for one day, like daylilies. There are two female flowers that open before dawn of the first day of the movie and the petals wither and collapse in the afternoon of the same day. The flowers are typically pollenated by honeybees and other insects. Female flowers that are not properly pollenated may start growing but usually abort within a few days after the flower opened. Once a female flower is pollinated, the ovary will begin to grow rapidly and after several weeks the fruit will mature. The female flower to the far right in the movie aborted after just a couple of days but the one in the middle went on to grow into a mature pumpkin fruit.

In the movie, you can tell day from night by the presence of moving shadows during the day. The images were captured with a flash at night so there are no moving shadows. Of course, you can also identify the night periods by the expanshion of the fruit. The movie shows about 10 days of growth. Images were captured every 5 min day and night.