Drought stress, plant water status, and floral trait expression in fireweed, Epilobium angustifolium (Onagraceae)

Abstract

In a controlled environment, we artificially induced drought during flowering of Epilobium angustifolium, an animal-pollinated plant. Leaf water potential (ψ(l)) and floral traits were monitored over a 12-d period of soil moisture depletion. Soil moisture depletion induced drought stress over time, as revealed by significant treatment × day interactions for predawn and midday ψ(l). Nectar volume and flower size showed significant negative responses to drought stress, but nectar sugar concentration did not vary between treatments. Floral traits were more buffered from drought than leaf water potentials. We used path analysis to examine direct and indirect effects of ψ(l) on floral traits for plants in well-watered (control) vs. drought treatments. According to the best-fit path models, midday ψ(l) has significant positive effects on flower size and nectar volume in both environments. However, for controls midday ψ(l) also had a significant negative effect on nectar sugar concentration. Results indicate that traits influencing floral attractiveness to pollinators in E. angustifolium vary with plant water status, such that pollinator-mediated selection could indirectly target physiological or biochemical controls on ψ(l). Moreover, under mesic conditions selection for greater nectar sugar reward may be constrained by the antagonistic effects of plant water status on nectar volume and sugar concentration.

Pattern of flower size variation along an altitudinal gradient differs between Impatiens textori and Impatiens noli-tangere

“…These environmental factors can affect flower size variation along the gradient (Galen 2000;Knight et al 2005;Parachnowitsch & Kessler 2010). For example, Galen (2000) and Carroll et al (2001) reported negative correlations between flower size and resource availability as related to environmental stress and suggested that these negative correlations reflected the increased physiological cost of producing large flowers when resource availability is poor as a result of high environmental stress. Further study is needed to test how variations in flower dimensions might relate to variations in the abundance, diversity, and visit rate of pollinators.…”

Analysis of biochemical variations and microRNA expression in wild (Ipomoea campanulata) and cultivated (Jacquemontia pentantha) species exposed to in vivo water stress

“…Drought tolerant species possess adaptive traits like decrease in leaf area along with thickening, sunken stomata, increase in root length and reduction in size of flowers (Carroll et al 2001;Maroco et al 2000;Turner 1994). Current study analyzes morphological, biochemical and molecular variations in two related plant species with contrasting stress sensitivities to water deficit.…”

Influence of Green Leaf Herbivory by Manduca sexta on Floral Volatile Emission by Nicotiana suaveolens

“…However, plants are challenged by constantly changing abiotic and biotic environmental conditions that might affect a plant's capacity to invest in sexual reproduction (Euler and Baldwin, 1996;Carroll et al, 2001;García and Ehrlén, 2002). Besides direct impacts, like floral oviposition (Dufaÿ and Anstett, 2003) or floral herbivory (Leege and Wolfe, 2002;Rö se and Tumlinson, 2004;Theis, 2006;Sanchez-Lafuente, 2007), flowers are mostly exposed to a changing environment as part of an entirely affected plant (Sampson and Cane, 1999;Carroll et al, 2001). One of the most deleterious biotic influences on plants is green leaf herbivory.…”