Influence of temperature shift after flowering on dry matter partitioning in two cultivars of snap bean (Phaseolus vulgaris) that differ in heat tolerance

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.