Growth of near-isogenic wheat lines differing in development - Spaced plants

The relationship between phenological development in wheat (Triticum aestivum L.) and growth was studied to determine if the switch from a vegetative to a reproductive apex increases plant growth rate. Plant partitioning and relative growth rates during vegetative and pre-flowering reproductive periods were determined in two sets of near-isogenic lines differing in phenological development. Spaced plants were grown in two photoperiods (15 and 10 h) to increase the range of development rates. Lines within each isogenic set and photoperiod treatment did not differ in whole plant growth rate despite large differences in developmental rate. In addition, the partitioning of biomass between roots and shoots was also similar. The transition of the apex from vegetative to reproductive mostly affected the partitioning of shoot biomass into leaf (blades) and stems (rest of the shoot). A longer time to reach floral initiation was associated with the production of more, and larger, leaves as well as more tillers. This resulted in large differences in leaf area between isolines. However, at the whole plant level, all lines accumulated biomass at the same rate with time. The early flowering lines compensated for their reduced leaf area by having a higher net assimilation rate and were thereby able to maintain the same relative growth rate as their later flowering counterparts. (C) 1998 Annals of Botany Company.