Architecture and morphogenesis of grain sorghum, Sorghum bicolor (L.) Moench

Plant architecture has been neglected in most studies of biomass allocation in crops. To help redress this situation for grain sorghum (Sorghum bicolo r (L.) Moench), we used a 3D digitiser to measure the dimensions and orient ations of vegetative and reproductive structures and derived thermal time-b ased functions for architectural changes during morphogenesis. Our plants, which were grown in a greenhouse, controlled environment cabinets and the f ield, covered a large, three-fold, size range when mature. This allowed us to detect some general architectural relationships and to fit morphogenetic functions common across the size range we observed. For example, the relat ionship between the lengths of successive fully-expanded leaves within a pl ant was nearly constant for all plants. The lengths of existing leaf blades were accurate predictors of the lengths of up to six subsequently-formed b lades in our plants. Similar constant relationships were detected for inter node lengths in the panicle and for heights above ground of the collars of successive leaves, even though these traits varied a lot between growth con ditions. We suggest that such architectural relationships may be used to li nk the effect of previous growth conditions to future growth potential, and in that way to predict future partitioning. Our results provide the basis for a preliminary model of sorghum morphogenesis which could eventually bec ome useful in conjunction with crop models by allowing resource acquisition to be related to changes in plant architecture during development. (C) 199 9 Elsevier Science B.V. All rights reserved.