REINTERPRETATION OF AN EXPERIMENT ON THE ROLE OF ASSIMILATE TRANSPORTRESISTANCE IN PARTITIONING IN TOMATO

The importance of transport resistance (distance between source and si nk) on assimilate partitioning in tomato is questioned. Slack and Calv ert (Journal of Horticultural Science 52 : 309-315, 1977) concluded th at, in tomato, excising of fruit trusses showed a direct influence of distance from source on assimilate partitioning. A dry matter distribu tion model for tomato, based on the hypothesis that distribution is re gulated by the sink strengths of the plant organs and that no influenc e of transport resistance on partitioning exists, has been described a nd validated by Heuvelink (Annals of Botany 77: 71-80, 1996). Using th is model, it is shown that the results of Slack and Calvert (1977) can be explained more simply on the basis of the succession of trusses wi th growth shifted with respect to time. Therefore, their results do no t prove that transport resistance plays a role in assimilate partition ing. (C) 1996 Annals of Botany Company