Comparative vegetative development of divaricating and arborescentSophoraspecies (Fabaceae)

Abstract

Morphometric parameters that have been used previously to define divaricates are not useful for the genus Sophora. In measurements of forestgrown material, only node-angles effectively distinguished between the arborescent S. tetraptera and the divaricating species S. prostrata and S. microphylla. We examined the developmental basis for the generation of divaricating architecture in Sophora species by following growth of potted material over one year. The divaricating form was characterised by a twice-yearly production of new branches; sylleptic outgrowth in the spring, and proleptic outgrowth towards late summer. Branches arose predominantly from the proximal node. By contrast, the arborescent species had only a single growth period, and proleptic branches were produced from more distal nodes. In all three species, growth was most extensive in the uppermost regions of the canopy. Developmental processes may be better descriptors of divarication than shoot dimensions.

120 Years of Untangling the Divaricate Habit: A Review

“…He 598 recommended the study of the changes in the branching sequence of many divaricate species over 599 their lifetime, as he believed this could be the only way to understand how the diversity of 600 divaricating habits was produced under a possibly single selective pressure, and to draw general 601 conclusions about their development. (Day 1998c); Sophora prostrata and the 606 juvenile form of Sophora microphylla (Carswell & Gould 1998). Overall, these studies concluded 607 that such a growth pattern, with many growing points scattered across the plant's crown, offers a 608 plastic structure that can more easily accommodate for changes in environmental conditions (e.g.…”