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

In a controlled environment, we artificially induced drought during flowering of Epilobium angustifolium, an animal-pollinated plant. Leaf water potential (ψ1) and floral traits were monitored over a 12-d period of soil moisture depletion. Soil moisture depletion induced drought stress over time, as...

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Bibliographic Details
Published in:American journal of botany 2001-03, Vol.88 (3), p.438-446
Main Authors: Carroll, Amy B., Pallardy, Stephen G., Galen, Candace
Format: Article
Language:English
Subjects:
Botany
Drought
drought stress
Epilobium angustifolium
flower size
Flowering
Flowers
Flowers & plants
leaf water potential
Nectar
nectar production
Nectar secretion
nectar sugar concentration
Onagraceae
phenotypic plasticity
Phenotypic traits
Plants
Pollinating insects
pollinator‐mediated selection
Reproductive Biology
Soil water
Sugars
Water
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Summary:In a controlled environment, we artificially induced drought during flowering of Epilobium angustifolium, an animal-pollinated plant. Leaf water potential (ψ1) 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 x day interactions for predawn and midday ψ1. 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 ψ1on floral traits for plants in well-watered (control) vs. drought treatments. According to the best-fit path models, midday ψ1has significant positive effects on flower size and nectar volume in both environments. However, for controls midday ψ1also 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 ψ1. 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.
ISSN:0002-9122
1537-2197
DOI:10.2307/2657108