Abstract
The partitioning of dry matter (ratio of dry weight of individual parts to that of total dry matter) was analyzed in snap bean cultivars, Haibushi, a heat-tolerant cultivar, and Kentucky Wonder, a heat-sensitive cultivar, at four temperatures after flowering on the subtropical island of Ishigaki, Japan. The temperature regimes included 27/23°C (day/night) as normal, 24/20°C as low, 30/26 as high, and 33/29°C as extremely high. Most growth traits increased after flowering time (35 DAS), displaying a plateau at 68-75 DAS. The total dry matter was similar under all temperature conditions, but differed with the cultivar. Haibushi had a higher value of total dry matter than Kentucky Wonder, which was mainly due to higher pod dry weight although stem and root dry weights were lower in Haibushi. A sharp decline of dry matter partitioning to pods was observed at 33/29°C. In the temperature range of 24/20 to 30/26°C, Haibushi showed higher partitioning to pods than Kentucky Wonder, independent of temperature. On the other contrary, Kentucky Wonder showed higher partitioning to pods at 27/23°C than at 24/20°C. These results showed that the partitioning of dry matter, which varied with the cultivar and temperature, played an important role in achieving higher harvest index in the heat-tolerant than in the heat-sensitive cultivars.
