MUTANT DN INFLUENCES DRY-MATTER DISTRIBUTION, ASSIMILATE PARTITIONING AND FLOWERING IN LATHYRUS-ODORATUS L

The flowering mutant dn in sweet pea was used as a tool to study C-14-assimilate and dry matter partitioning with respect to nutrient diversion theories on the control of flower initiation. Wild type plants (Dn(h)) are photoperiodic and exhibit late flowering and profuse basal branching in short days while mutant plants (dn) are day neutral, early flowering and devoid of basal laterals. In short days, dn plants exported a significantly greater proportion of assimilate acropetally than Dn(h) plants and the upper portion of dn plants had a greater dry weight. These differences were reduced dramatically when basal laterals were excised regularly from the Dn(h) plants although the difference in flowering remained. However, the effect of dn on resource allocation within the apical region may be more important in regard to flowering than the effect on acropetal versus basipetal movement. In short days, the dn plants partitioned significantly more resources into their internodes and petioles, and less into their leaflets, than Dn(h) plants as shown by dry weight and C-14-assimilate measurements. These differences were apparent from as early as node 7 up to the node of flower initiation in dn plants (approximately node 30) and they were not eliminated by removal of basal laterals from Dn(h) plants. Differences between dn and Dn(h) plants in partitioning and flowering were largely eliminated under long days. The fact that in this species a single gene influences both resource allocation and flower initiation lends further support to nutrient diversion hypotheses on the control of flowering.