Dong-nong 704, Mao-fen 802, L402, P74100 and 02276 were used to investigate the factors influencing heat-tolerance of tomato. The results showed that the permeability of plasma membrane, MDA contents of leaves were negatively related with heat-tolerance of tomato, while SOD activity and proline content were positively related with heat-tolerance of tomato. There are some differences of each index among tomato varieties. This suggested that the permeability of plasma membrane, SOD activity and proline conten...