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Solar activity has a significant influence on Earth's climate and may drive many biological processes. Here, we measured growth in 11 tree species distributed along an ≈600‐km latitudinal gradient in South‐Central Chile, recording the width of their growth‐rings among periods of maximum (highest number of sunspots) and minimum (lowest number of sunspots) solar activity. In one of these species, Quillaja saponaria, we experimentally assessed three ecophysiological traits (CO2 fixation through photosynthesis [Amax], growth and leaf production) as well as the expression of five genes related to cell wall elongation and expansion following exposure to high and low levels of UV‐B radiation, simulating scenarios of maximum and minimum solar activity, respectively. We found lower tree growth during the periods of maximum solar activity, with this trend being more evident at lower latitudes, where UV‐B radiation is higher. Exposure of Q. saponaria to higher levels of UV‐B affected the ecophysiological parameters, revealing a decrease in Amax, growth and leaf production. In addition, higher levels of UV‐B led to repression in four of the five genes studied. Our results may help foresee environmental scenarios for different plant species associated with solar activity. [ABSTRACT FROM AUTHOR]

Premise of research. Tolerance to herbivory is the capacity of plants to reduce the negative effects of damage on fitness. Increased growth rate and photosynthesis are two important mechanisms behind tolerance to herbivory. The chlorophyll fluorescence parameter F v / F m , which reflects photosynthetic performance, has been used to characterize stress effects on plants. Here, we tested the hypothesis that photosynthetic performance, estimated from F v / F m , may predict tolerance to herbivory. Methodology. In the greenhouse, we evaluated whether F v / F m values measured in recently damaged seedlings of the temperate rainforest tree Aextoxicon punctatum predict relative growth rate (RGR) measured 30 d after damage. RGR was earlier associated with tolerance to herbivory in tree species from this forest. In the field, we determined whether F v / F m values in experimentally damaged seedlings of 13 tree species are correlated with their reported levels of tolerance to herbivory. Pivotal results. RGR showed positive associations with F v / F m measured 3 h and 30 d after damage but no association with F v / F m measured before damage. In undamaged control seedlings, RGR was not related to F v / F m at any time evaluated. The across-species comparison in the field showed that F v / F m values were positively correlated with reported levels of tolerance to herbivory. Conclusions. The parameter F v / F m is an accurate predictor of RGR and tolerance to herbivore damage. We advocate the use of this rapid methodology to estimate plant tolerance to herbivory in natural populations. [ABSTRACT FROM AUTHOR]

Abstract: Aim: Crassulacean acid metabolism (CAM) is a widespread physiological adaptation to drought. CAM is common in plants distributed in arid regions, such as Bromeliaceae species. In Chile, latitude is an accurate predictor of climate, with increasing temperature and decreasing moisture towards north. Northern species of Chilean bromeliads mainly show CAM photosynthesis, while southern‐distributed species rely on the C3 pathway. We evaluated the influence of latitude and associated climatic variables on the adoption of photosynthetic pathways by Chilean bromeliads, accounting for phylogenetic relatedness. We expected a significant relation between photosynthetic pathway and the latitudinal limits of species’ distribution ranges, independent of phylogeny. Location: Data from Bromeliaceae species native to Chile (latitudinal distribution range: 15°S to 43°S). Methods: We gathered information on geographical ranges and isotopic discrimination data (δ13C, an indicator of photosynthetic pathway) of Chilean bromeliads. We evaluated whether δ13C values were related to latitude, temperature and precipitation using separate multiple linear regressions in northern and southern distribution limits of Chilean bromeliads. To account for phylogeny, we performed phylogenetically independent contrasts. Results: In the south, δ13C values were not significantly correlated with latitude, temperature or precipitation. In the north, δ13C values were significantly correlated with latitude and annual precipitation. After phylogenetic correction, both variables were still significantly associated with δ13C. Main conclusions: In Chilean bromeliads, for those taxa reaching northernmost latitudes both aridity and other factors associated with latitude are probably the main drivers of adaptive evolution of CAM photosynthesis while advancing towards their present limits in arid regions. Phylogenetic relatedness also influences CAM photosynthesis in this lineage. [ABSTRACT FROM AUTHOR]

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Climbing plants are a key component of rainforests, but mechanistic approaches to their distribution and abundance are scarce. In a southern temperate rainforest, we addressed whether the dominance of climbing plants across light environments is associated with the expression of ecophysiological traits. In mature forest and canopy gaps, we measured leaf size, specific leaf area, photosynthetic rate, and dark respiration in six of the most abundant woody vines. Mean values of traits and their phenotypic change (%) between mature forest and canopy gaps were predictor variables. Leaf size and specific leaf area were not significantly associated with climbing plant dominance. Variation in gas-exchange traits between mature forest and canopy gaps explained, at least partly, the dominance of climbers in this forest. A greater increase in photosynthetic rate and a lower increase in dark respiration rate when canopy openings occur were related to the success of climbing plant species. Dominant climbers showed a strategy of maximizing exploitation of resource availability but minimizing metabolic costs. Results may reflect phenotypic plasticity or genetic differentiation in ecophysiological traits between light environments. It is suggested that the dominant climbers in this temperate rainforest would be able to cope with forest clearings due to human activities. [ABSTRACT FROM AUTHOR]

Crassulacean acid metabolism (CAM) is a photosynthetic pathway that significantly increases water use efficiency in plants. It has been proposed that CAM photosynthesis, which evolved from the ancestral C3 pathway, has played a role in the diversification of some prominent plant groups because it may have allowed them to colonize and successfully spread into arid or semi-arid environments. However, the hypothesis that CAM photosynthesis constitutes an evolutionary key innovation, thereby enhancing diversification rates of the clades possessing it, has not been evaluated quantitatively. We tested whether CAM photosynthesis is a key innovation in the Bromeliaceae, a large and highly diversified plant family that has successfully colonized arid environments. We identified five pairs of sister groups with and without the CAM feature, including 31 genera and over 2000 species. In all five cases, the clades with CAM photosynthesis were more diverse than their C3 counterparts. We provide quantitative evidence that the evolution of CAM photosynthesis is significantly associated with increased diversification in Bromeliaceae and thus constitutes an evolutionary key innovation. We also found preliminary evidence of an association between the CAM pathway and growth habit in bromeliads, with terrestrial species being more likely to show CAM photosynthesis than epiphytic species. To our knowledge, this is the first case of a physiological attribute shown to be a key innovation in plants. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 480-486. [ABSTRACT FROM AUTHOR]

Abstract: Plant tolerance is the ability to reduce the negative impact of herbivory on plant fitness. Numerous studies have shown that plant tolerance is affected by nutrient availability, but the effect of soil moisture has received less attention. We evaluated tolerance of apical damage (clipping that mimicked insect damage) under two watering regimes (control watering and drought) in the tarweed Madia sativa (Asteraceae). We recorded number of heads with seeds and total number of heads as traits related to fitness. Net photosynthetic rate, water use efficiency, number of branches, shoot biomass, and the root:shoot biomass ratio were measured as traits potentially related to tolerance via compensatory responses to damage. In the drought treatment, damaged plants showed ≈43% reduction in reproductive fitness components in comparison with undamaged plants. In contrast, there was no significant difference in reproductive fitness between undamaged and damaged plants in the control watering treatment. Shoot biomass was not affected by apical damage. The number of branches increased after damage in both water treatments but this increase was limited by drought stress. Net photosynthetic rate increased in damaged plants only in the control watering treatment. Water use efficiency increased with drought stress and, in plants regularly watered, also increased after damage. Root:shoot ratio was higher in the low water treatment and damaged plants tended to reduce root:shoot ratio only in this water treatment. It is concluded that water availability limits tolerance to apical damage in M. sativa, and that putative compensatory mechanisms are differentially affected by water availability. [Copyright &y& Elsevier]