EFFECT OF FRUIT LOAD ON DRY-MATTER PARTITIONING IN TOMATO

Greenhouse experiments in which tomato plants were grown for about 100 days at different levels of fruit removal, showed a strong influence of fruit load on assimilate partitioning between vegetative and genera tive plant parts. The fraction of dry matter distributed to the fruits (F-fruits) in the last weeks of the experiments when an almost consta nt distribution of dry matter was reached, could accurately be describ ed by a saturation-type function of the number of fruits retained per truss (n(f)): F-fruits=n(f)/(2.96+/-n(f)). Hence, generative sink stre ngth was proportional to the number of fruits in the range two to seve n fruits per truss, and the average sink strength of a vegetative unit (three leaves and the stem internodes between two trusses) was 2.96 t imes the average sink strength of one fruit. In an experiment with eit her no truss pruning or every other truss removed at anthesis, the ave rage fraction of dry matter distributed to the fruits, over a time int erval between two destructive measurements, increased with average fru it number on the plant (N-f) during this time interval and could be de scribed by: F-fruits=N-f(24.2+N-f), which is consistent with the relat ionship between F-fruits and n(f). The weight of individual fruits inc reased with decreasing number of fruits per plant, albeit less than pr oportionally. (C) 1997 Elsevier Science B.V.