Introduced populations of the garden lupine are adapted to local generalist snails but have lost alkaloid diversity

Intraspecific variation in growth and defence among plant populations can be driven by differences in (a)biotic conditions, such as herbivory and resources. Introduction of species to novel environments affects simultaneously herbivory encountered by a plant and resource availability both directly and via altered competitive environment. Here, we address the question of how growth (leaf mass per area (LMA), plant size) and resistance traits (leaf alkaloids, leaf trichomes, resistance to a generalist snail) vary and covary between native and introduced populations of the garden lupine, Lupinus polyphyllus. We focused specifically on evolved differences among populations by measuring traits from plants grown from seed in a common environment. Plants from the introduced populations were more resistant against the generalist snail, Arianta arbustorum, and they had more leaf trichomes and higher LMA than plants from the native populations. The composition of alkaloids differed between native and introduced populations, with the native populations having more diversity in alkaloids among them. Resistance was positively associated with plant size and LMA across all populations. Other trait associations differed between native and introduced areas, implying that certain trade-offs may be fundamentally different between native and introduced populations. Our results suggest that, for the introduced populations, the loss of native herbivores and the alterations in resource availability have led to a lower diversity in leaf alkaloids among populations and may facilitate the evolution of novel trait optima without compensatory trade-offs. Such phytochemical similarity among introduced populations provides novel insights into mechanisms promoting successful plant invasions.

The Essential Oil Composition of Trachymene incisa Rudge subsp. incisa Rudge from Australia

Trachymene incisa subsp. incisa is an Australian endemic taxon that varies greatly in the abundance and length of the leaf trichomes. The essential oil composition of five populations of this subspecies, three corresponding to the typical glabrous form and two of the particularly hairy variant, has been analyzed in an attempt to determinate if that variability is also reflected in their composition. The oils have been extracted by hydrodistillation and analyzed by Gas Chromatography (GC) and Gas Chromatography coupled to Mass Spectrometry (GC–MS). The essential oils of T. incisa subsp. incisa were characterized by the high amount of sesquiterpenes that were the major fraction. The sesquiterepene hydrocarbons were significantly higher in the hairy variant in comparison to the glabrous one. According to the main compound, three different chemotypes were found: I.—β-selinene + bicyclogermacrene and II.—γ-bisabolene + α-pinene for the typical glabrous variant and III.—bicyclogermacrene + β-caryophyllene for the hairy variant.

Arabidopsis thaliana zinc accumulation in leaf trichomes is correlated with zinc concentration in leaves

Zinc (Zn) is a key micronutrient for plants and animals, and understanding Zn homeostasis in plants can improve both agriculture and human health. While root Zn transporters in plant model species have been characterized in detail, comparatively little is known about shoot processes controlling Zn concentrations and spatial distribution. Previous work showed that Zn hyperaccumulator species such as Arabidopsis halleri accumulate Zn and other metals in leaf trichomes. To date there is no systematic study regarding Zn accumulation in the trichomes of the non-accumulating, genetic model species A. thaliana. Here, we used Synchrotron X-Ray Fluorescence mapping to show that Zn accumulates at the base of trichomes of A. thaliana. Using transgenic and natural accessions of A thaliana that vary in bulk leaf Zn concentration, we demonstrate that higher leaf Zn increases total Zn found at the base of trichome cells. Our data indicates that Zn accumulation in trichomes is a function of the Zn status of the plant, and provides the basis for future studies on a genetically tractable plant species to understand the molecular steps involved in Zn spatial distribution in leaves.

The Essential Oil Composition of Trachymene Incisa Rudge Subsp. Incisa Rudge From Australia

Trachymene incisa subsp. incisa is an Australian endemic taxon that varies greatly in the abundance and length of the leaf trichomes. The essential oil composition of five populations of this subspecies, three corresponding to the typical glabrous form and two of the particularly hairy variant, has been analyzed in an attempt to determinate if that variability is also reflected in their composition. The oils have been extracted by hydrodistillation and analysed by Gas Chromatography (GC) and Gas Chromatography coupled to Mass Spectrometry (GC-MS). The essential oils of T. incisa subsp. incisa were characterized by the high amount of sesquiterpenes that were the major fraction. The sesquiterepene hydrocarbons were significantly higher in the hairy variant in comparison to the glabrous one. According to the main compound three different chemotypes were found: I.- -selinene + bicyclogermacrene and II.- -bisabolene + -pinene for the typical glabrous variant and III.- bicyclogermacrene + -caryophyllene for the hairy variant.

Roles of leaf trichomes in heat transfers and gas‐exchange characteristics across environmental gradients

Dense leaf trichomes can directly decrease gas fluxes through increased gas diffusion resistance and indirectly increase gas fluxes through increased leaf temperature due to increased heat diffusion resistance, which may contribute to adaptation to dry and/or low‐temperature conditions. However, it remains unclear whether the leaf‐trichome resistance increases or decreases the gas‐exchange rates through combined direct and indirect effects. We focused on Metrosideros polymorpha, a dominant tree species inhabiting a large range of environmental gradients in the Hawaiian Islands, whose leaves have an enormous variation in trichome thickness on the lower surface. In five elevational sites, we measured leaf morphological and physiological traits including trichome thickness, gas‐exchange characteristics, and leaf temperature. The trichome thickness was largest in the coldest and driest site and thinnest at the wettest site. Leaf temperature was significantly increased with trichome thickness. With biophysical and physiological models, we show that leaf trichomes can increase the daily photosynthesis through increasing leaf temperature only in the cold alpine area. The daily water‐use efficiency can be lower with increasing leaf trichomes at any elevational sites. Therefore, in terms of diffusion resistance, the leaf trichomes of M. polymorpha can contribute to the adaptation to low‐temperature environments but not to dry environments.