title: Architectural plasticity in a Mediterranean winter annual.
abstract: Size variability in plants may be underlain by overlooked components of architectural plasticity. In annual plants, organ sizes are expected to depend on the availability and reliability of resources and developmental time. Given sufficient resources and developmental time, plants are expected to develop a greater number of large branches, which would maximize fitness in the long run. However, under restrictive growth conditions and environmental reliability, developing large branches might be risky and smaller branches are expected to foster higher final fitness. Growth and architecture of Trifolium purpureum (Papilionaceae) plants from both Mediterranean (MED) and semi-arid (SAR) origins were studied, when plants were subjected to variable water availability, photoperiod cues and germination timing. Although no clear architectural plasticity could be found in response to water availability, plants subjected to photoperiod cuing typical to late spring developed fewer basal branches. Furthermore, plants that germinated late were significantly smaller, with fewer basal branches, compared with plants which grew for the same time, starting at the beginning of the growing season. The results demonstrate an intricate interplay between size and architectural plasticities, whereby size modifications are readily induced by environmental factors related to prevalent resource availability but architectural plasticity is only elicited following the perception of reliable anticipatory cues.
authors.affiliation: Mitrani Department of Desert Ecology, Blaustein Institutes for Desert Research, Ben-Gurion University of the Negev, Midreshet Ben-Gurion, Israel.
authors.forename: Hagai
authors.initials: H
authors.lastname: Shemesh
authors.forename: Benjamin
authors.initials: B
authors.lastname: Zaitchik
authors.forename: Tania
authors.initials: T
authors.lastname: Acuña
authors.forename: Ariel
authors.initials: A
authors.lastname: Novoplansky
mesh_terms: D018533:Biomass; D002980:Climate; D018525:Germination / Q000502:physiology; D019083:Mediterranean Region; D017440:Photoperiod; D018520:Plant Shoots / Q000033:anatomy & histology; D012621:Seasons; D013997:Time Factors; D029921:Trifolium / Q000033:anatomy & histology* / Q000254:growth & development