Effects of fluctuating temperature on mulberry sapling growth and dry matter accumulation

The prediction of mulberry (Morus alba L.) growth becomes important for changes in the mulberry cultivation system. To develop a mulberry growth model, the response of mulberry growth to different temperatures was investigated. Mulberry saplings were grown in phytotorons under sunlight at 3 diurnally fluctuating temperature conditions (34/22, 32/24, 30/26°C) which were a 28°C average daily temperature and at 2 constant temperatures (28, 32°C) in 1995, and at 4 fluctuating temperatures (33/19, 32/20, 30/22, 28/24°C) which were a 26°C average daily temperature and at one constant temperature (26°C) in 1996. The shoot length and leaf number were investigated every 10 days. Distribution of dry matter to each plant part was measured at the end of the treatment. Changes in shoot length were not different among temperature treatments and the rate of shoot elongation increased in the process of time during the treatments in 1995, but leveled off at the end of treatment in 1996. There were no differences in leaf number among the same average daily temperature treatments in either years, but the leaf number between 32°C treatment and the other average daily 28°C treatments in 1995 was significantly different at a 1% level. Shoot dry weight was not different among temperature treatments in both years. Therefore, fluctuating temperature conditions seemed not to affect mulberry growth as long as the average daily temperature was same. The leaf number seemed to be a superior index of mulberry growth.