Unpredicted, rapid and unintended structural and functional changes occurred during early domestication of Silphium integrifolium, a perennial oilseed.

MAIN CONCLUSION: Selection for increased yield changed structure, physiology and overall resource-use strategy from conservative towards acquisitive leaves. Alternative criteria can be considered, to increase yield with less potentially negative traits. We compared the morphology, anatomy and physiology of wild and semi-domesticated (SD) accessions of Silphium integrifolium (Asteraceae), in multi-year experiments. We hypothesized that several cycles of selection for seed-yield would result in acquisitive leaves, including changes predicted by the leaf economic spectrum. Early-selection indirectly resulted in leaf structural and functional changes. Leaf anatomy changed, increasing mesophyll conductance and the size of xylem vessels and mesophyll cells increased. Leaves of SD plants were larger, heavier, with lower stomatal conductance, lower internal CO2 concentration, and lower resin concentration than those of wild types. Despite increased water use efficiency, SD plants transpired 25% more because their increase in leaf area. Unintended and undesired changes in functional plant traits could quickly become fixed during domestication, shortening the lifespan and increasing resource consumption of the crop as well as having consequences in the provision and regulation of ecosystem services.

Reproductive allocation of biomass and nitrogen in annual and perennial Lesquerella crops.

BACKGROUND AND AIMS: The use of perennial crops could contribute to increase agricultural sustainability. However, almost all of the major grain crops are herbaceous annuals and opportunities to replace them with more long-lived perennials have been poorly explored. This follows the presumption that the perennial life cycle is associated with a lower potential yield, due to a reduced allocation of biomass to grains. The hypothesis was tested that allocation to perpetuation organs in the perennial L. mendocina would not be directly related to a lower allocation to seeds. * METHODS: Two field experiments were carried on with the annual Lesquerella fendleri and the iteroparous perennial L. mendocina, two promising oil-seed crops for low-productivity environments, subjected to different water and nitrogen availability. * KEY RESULTS: Seed biomass allocation was similar for both species, and unresponsive to water and nitrogen availability. Greater root and vegetative shoot allocation in the perennial was counterbalanced by a lower allocation to other reproductive structures compared with the annual Lesquerella. Allometric relationships revealed that allocation differences between the annual and the perennial increased linearly with plant size. The general allocation patterns for nitrogen did not differ from those of biomass. However, nitrogen concentrations were higher in the vegetative shoot and root of L. mendocina than of L. fendleri but remained stable in seeds of both species. * CONCLUSIONS: It is concluded that vegetative organs are more hierarchically important sinks in L. mendocina than in the annual L. fendleri, but without disadvantages in seed hierarchy.