Cultivar and seasonal effects on the contribution of pre-anthesis assimilates to safflower yield

in crops grown under Mediterranean environments, translocation of pre-anthesis assimilates to the seed is of great importance for seed growth, because hot and dry conditions during the seed filling period diminish photosynthesis and crop nitrogen uptake. This field study was conducted to assess the genetic and seasonal variation in the amount of pre-anthesis dry matter and nitrogen accumulated and translocated to seed by safflower (Carthamus tinctorius L.) plants, and the possible N losses occurring between anthesis and maturity. Ten genotypes, 4 hybrids and 6 open pollinated cultivars, were grown for 2 growing seasons without irrigation, on a silty clay (Typic Xerorthent) soil. The proportion of dry matter and N content at anthesis that was translocated to seed differed among genotypes and ranged from 14.9 to 39.6 and from 24.8-59.3%, respectively. Genotypic differences in dry matter and N translocation were mainly associated with dry matter and N accumulated during the vegetative growth of the plants. Greater amounts of dry matter and N content at anthesis resulted in a greater dry matter and N translocation to seed during the filling period. When the N contents of aboveground plant parts at anthesis and maturity were compared, both gains and losses were observed, and were mainly related to the sink size. No N losses were detected when yield was high. When yield was low, N losses depended on N content at anthesis; high N content resulted in N losses, otherwise no N losses were observed. The contribution of pre-anthesis accumulated reserves to seed weight ranged from 64.7 to 92.2%, indicating the importance of pre-anthesis storage of assimilates for attaining high safflower yield. (C) 2004 Elsevier B.V. All rights reserved.