Browsing by Author "Atala, Cristian"

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    Drought and leaf damage limit the search for support in the climbing plant Ipomoea purpurea (L.) Roth (Convolvulaceae)
    (2011) Atala, Cristian; Cordero, Cristian; Gianoli, Ernesto
    There is evidence that some climbing plants increase their twining rate after leaf damage, thus avoiding ground herbivores, and that drought limits this induced response. However, it is unknown whether leaf damage and drought affect the search for support, an ecologically relevant process for climbing plants. We evaluated the combined effect of drought and leaf damage on support searching in the twining vine Ipomoea pupurea (Convolvulaceae). Plants were assigned to a combination of three watering treatments (regular watering, moderate drought, and severe drought) and two damage treatments (control and 50% defoliation). We placed a stake at 15 cm from the stem and recorded the time to successful twining (360 degrees turn). We also measured some plant functional traits to explore possible mechanisms. Leaf damage decreased time to successful twining in all treatments with the exception of severe drought. Severe drought decreased plant growth, particularly when combined with leaf damage. In nature, climbing plants are usually not in contact with a support in the early stages. The searching behavior seems to increase with leaf damage, but it is restricted by water shortage. Plants experiencing both leaf damage and severe drought will be less likely to find a support, resulting in higher probability of further leaf damage.
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    DROUGHT LIMITS INDUCED TWINING BY LEAF DAMAGE IN THE CLIMBING PLANT IPOMOEA PURPUREA (L.) ROTH (CONVOLVULACEAE)
    (2009) Atala, Cristian; Gianoli, Ernesto
    The environment may limit the expression of induced responses to herbivory, Such as increased chemical or physical defenses. Recent studies in climbing plants have shown that leaf damage induces twining. This response may confer protection against ground herbivores in the field. We addressed the effect of drought oil the induced twining of the annual vine Ipomoea purpurea (Convolvulaceae), which can experience drought stress in natural conditions. In a greenhouse experiment, we recorded twining rate (proportion of plants successfully climbing at a given time) of damaged and undamaged individuals of I. purpurea Subjected to control watering and water shortage treatments. We also estimated stem growth rate and stem water content in experimental plants, just after the evaluation of climbing Success. Plants in the drought treatment showed reduced twining induction by leaf damage compared to control plants. Neither stem growth nor stem water content were affected by leaf damage or drought. Results Suggest that drought constrains the induced twining through mechanisms not directly related to stein growth and water content. It is Suggested that drought might trigger signals that counteract those elicited by leaf damage. The induced twining may be an advantage in the presence of ground herbivores, but the environmental susceptibility of this response may limit its ecological significance.
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    Effect of water availability on tolerance of leaf damage in tall morning glory, Ipomoea purpurea
    (2009) Atala, Cristian; Gianoli, Ernesto
    Resource availability may limit plant tolerance of herbivory. To predict the effect of differential resource availability on plant tolerance, the limiting resource model (LRM) considers which resource limits plant fitness and which resource is mostly affected by herbivore damage. We tested the effect of experimental drought on tolerance of leaf damage in Ipomoea purpurea, which is naturally exposed to both leaf damage and summer drought. To seek mechanistic explanations, we also measured several morphological, allocation and gas exchange traits. In this case, LRM predicts that tolerance would be the same in both water treatments. Plants were assigned to a combination of two water treatments (control and low water) and two damage treatments (50% defoliation and undamaged). Plants showed tolerance of leaf damage, i.e., a similar number of fruits were produced by damaged and undamaged plants, only in control water. Whereas experimental drought affected all plant traits, leaf damage caused plants to show a greater leaf trichome density and reduced shoot biomass, but only in low water. It is suggested that the reduced fitness (number of fruits) of damaged plants in low water was mediated by the differential reduction of shoot biomass, because the number of fruits per shoot biomass was similar in damaged and undamaged plants. Alternative but less likely explanations include the opposing direction of functional responses to drought and defoliation, and resource costs of the damage-induced leaf trichome density. Our results somewhat challenge the LRM predictions, but further research including field experiments is needed to validate some of the preliminary conclusions drawn. (C) 2008 Elsevier Masson SAS. All rights reserved.
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    Phenotypic plasticity and performance of Taraxacum officinale (dandelion) in habitats of contrasting environmental heterogeneity
    (2010) Molina-Montenegro, Marco A.; Atala, Cristian; Gianoli, Ernesto
    Ecological theory predicts a positive association between environmental heterogeneity of a given habitat and the magnitude of phenotypic plasticity exhibited by resident plant populations. Taraxacum officinale (dandelion) is a perennial herb from Europe that has spread worldwide and can be found growing in a wide variety of habitats. We tested whether T. officinale plants from a heterogeneous environment in terms of water availability show greater phenotypic plasticity and better performance in response to experimental water shortage than plants from a less variable environment. This was tested at both low and moderate temperatures in plants from two sites (Corvallis, Oregon, USA, and El Blanco, Balmaceda, Chile) that differ in their pattern of monthly variation in rainfall during the growth season. We compared chlorophyll fluorescence (photosynthetic performance), flowering time, seed output, and total biomass. Plants subjected to drought showed delayed flowering and lower photosynthetic performance. Plants from USA, where rainfall variation during the growth season was greater, exhibited greater plasticity to water shortage in photosynthetic performance and flowering time than plants from Chile. This was true at both low and moderate temperatures, which were similar to early- and late-season conditions, respectively. However, phenotypic plasticity to decreased water availability was seemingly maladaptive because under both experimental temperatures USA plants consistently performed worse than Chile plants in the low water environment, showing lower total biomass and fewer seeds per flower head. We discuss the reliability of environmental clues for plasticity to be adaptive. Further research in the study species should include other plant traits involved in functional responses to drought or potentially associated with invasiveness.