ABOVEGROUND CARBOHYDRATE AND NITROGEN PARTITIONING IN COMMON VETCH DURING SEED FILLING

During seed filling in annual legumes, changes in concentration of ass imilates occur simultaneously with plant partitioning, leading to net changes in yield of assimilates derived from the processes of accumula tion and redistribution. Field studies were conducted during two growi ng seasons (1991-1992 and 1992-1993) in central Spain with the objecti ves of determining models of change for assimilate concentrations with advancing maturity and assessing efficiency of assimilate harvest rel ative to seed maturation. Concentration of total N, starch, total solu ble sugars (TSS), neutral-detergent fiber (NDF), acid-detergent fiber (ADF), and acid-detergent lignin (ADL) were determined in plant parts (seed, pod-shell, leaf, and stem) of common vetch (Vicia saliva L.) at seven maturity stages defined as progressively higher dry matter (DM) content in the seed (200-250, 250-300, 350-450, 450-550, 600-700, 700 -800, and >800 g DM kg(-1) seed). Concentration of assimilates in plan t parts changed over the whole seed-filling period. During the phase o f rapid seed growth (from 200-250 to 450-550 g DM kg(-1) seed), assimi lation was dominant for starch (net gain of 1086 kg ha(-1)), redistrib ution for TSS (net loss of 104 kg ha(-1)), and both process were opera tive in total N (net gain of 193 kg ha(-1)). During the ripening phase (from 450-550 to >800 g DM kg(-1) seed), most chemical components exc ept ADL showed a net loss. Maximum total accumulation for most mobile fractions except TSS was reached at the 450 to 550 g DM kg(-1) seed ma turity stage. Harvesting common vetch at this stage would represent ma ximum efficiency for total N and starch. Concentrations of nonstructur al chemical components had a nonlinear trend while concentration of fi ber fractions and lignin in vegetative structures showed a linear incr easing trend over the seed filling phase of common vetch.