Patterns of Growth, Development and Herbivory of Palicourea Rigida Are Affected More by Sun/Shade Conditions Than by Cerrado Phytophysiognomy
Total Page:16
File Type:pdf, Size:1020Kb
Acta Botanica Brasilica - 31(2): 286-294. April-June 2017. doi: 10.1590/0102-33062016abb0446 Patterns of growth, development and herbivory of Palicourea rigida are affected more by sun/shade conditions than by Cerrado phytophysiognomy Renan Fernandes Moura1*, Estevão Alves-Silva2 and Kleber Del-Claro3 Received: December 14, 2016 Accepted: April 17, 2017 . ABSTRACT Plant development is infl uenced by several abiotic factors, which in turn infl uence morphological traits and life history. We investigated whether leaf area, herbivory, toughness, fl uctuating asymmetry, structural complexity and the number of infl orescences of Palicourea rigida are infl uenced by sun/shade conditions or by Cerrado phytophysiognomy (typical cerrado or rupestrian fi eld). We expected to fi nd greater structural complexity, leaf toughness and more infl orescences in sun plants; shaded plants were expected to exhibit a greater degree of fl uctuating asymmetry (an index of plant stress), reduced leaf toughness and greater herbivory. As for phytophysiognomies, we expected to fi nd higher levels of leaf toughness and reduced structural complexity in plants from the rupestrian fi eld. We sampled plants in the sun and shade from both phytophysiognomies. Leaf area, toughness, herbivory and fl uctuating asymmetry, were infl uenced more by sun/shade conditions than phytophysiognomy; leaf toughness was the only variable to show greater values in conditions of sun. Our results indicate that exposure to sunlight is not a requirement for increased plant development, but plants in shade are experiencing stress, as shown by increased fl uctuating asymmetry; increased leaf area, a strategy to compensate for lower light exposure for plants and higher herbivory, which depicts lower toughness. Keywords: Brazilian savanna, environmental stress, fl uctuating asymmetry, leaf area loss, Rubiaceae, rupestrian grassland Introduction distinct morphological and functional characteristics. In areas where light is not a limiting factor, plants show a higher photosynthetic rate and tendency to produce thicker leaves, Plants are sessile organisms able to acclimate their ontogeny to diff erent environmental conditions (Rozendaal raising the amount of nitrogen available to the photosynthetic et al. 2006; Jan et al. 2013). An effi cient way of acclimation machinery (Björkman 1981; Gulmon & Chu 1981). However, exhibited by plants occurs through the modifi cation of in some cases, the excess of light may represent a stress leaves in order to optimise light capture (Bongers & Popma for plants, causing them to cool their leaves by increasing 1988; Raven et al. 2005). Individuals in a population of evapotranspiration (Givnish 1984). In contrast, plants in plants distributed in shaded and illuminated areas present shaded areas may enhance the effi ciency of light capture 1 Programa de Pós-Graduação em Ecologia e Conservação de Recursos Naturais, Universidade Federal de Uberlândia, AV. Pará, 1720, 38405-320, Umuarama, Uberlândia, MG, Brazil 2 Universidade do Estado de Mato Grosso, Rua Prof. Dr. Renato Figueiro Varella s/n, P. O. Box 08, 78690-000, Nova Xavantina, MT, Brazil 3 Instituto de Biologia, Universidade Federal de Uberlândia, Rua Ceará, 2D, Umuarama, 38405-320, Uberlândia, MG, Brazil * Corresponding author: [email protected] Diagramação e XML SciELO Publishing Schema: www.editoraletra1.com.br Patterns of growth, development and herbivory of Palicourea rigida are affected more by sun/shade conditions than by Cerrado phytophysiognomy by increasing leaf area (Evans & Poorter 2001; Valladares We studied individuals of Palicourea rigida, which is a et al. 2007). This increase enables plants to maintain common and attractive plant found in many Cerrado their photosynthetic rate as do plants in sunnier areas. phytophysiognomies (Ratter et al. 2003; Ribeiro & Walter Nonetheless, this is followed by a reduction of leaf toughness 2008). Plants were sampled in natural sun/shade conditions (Björkman 1981; Sims & Pearcy 1989), which is a measure in two different Cerrado phytophysiognomies, including a of mechanic resistance and an important factor of plant plateau with typical cerrado vegetation and a rupestrian defence against herbivory (Lucas et al. 2000; Korndörfer & field with rocky soils. These phytophysiognomies present Del-Claro 2006; Read & Stokes 2006; Peeters et al. 2007). For distinct soil characteristics; the rocky soil of rupestrian early successional plant species, shade also may be classified field, for instance, is rich in aluminum (Benites et al. 2003; as a stressing environmental condition, because these plants Negreiros et al. 2008). Aluminum is well-known by its toxic are naturally adapted to and depend on sunlight exposure effects in many plant species, mostly by its capacity of soil for their development (Venâncio et al. 2016a). acidification; this metal is also related to leaf toughness Sunlight exposure is an important factor responsible for the (Foy et al. 1978; Ma et al. 2001). Considering the distinct growth and development of plants and may influence several abiotic conditions provided by both microhabitat and traits and even fitness (Lomônaco & Reis 2007; Pascarella et Cerrado phytophysiognomies, we hypothesised that plant al. 2007; Venâncio et al. 2016b). For instance, differences in parameters are affected by both factors. structural complexity (e.g., number of leaves, height, canopy, As for our predictions, we expected to find increased trunk diameter) are common in plants growing in different levels of leaf area and FA in plants in the shade compared habitats (Farnsworth & Ellison 1996), and this could ultimately to plants in the sun. FA is a measure of plant stress; thus, influence plant performance and attractiveness to herbivores shaded plants were expected to show increased FA and (Lawton 1983; Alves-Silva & Del-Claro 2014). leaf area to intercept more light. We expected higher Environmental stress, including light deficiency and leaf toughness in sunny plants, owing to increased plant intense herbivory, can induce other biological responses in performance in the sun (Björkman 1981; Gulmon & Chu plants (Velasque & Del-Claro 2016), for instance, regarding 1981; Sims & Pearcy 1989) and lower values of herbivory developmental instability (Puerta-Piñero et al. 2008; Alves- (Lucas et al. 2000; Korndörfer & Del-Claro 2006; Read & Silva & Del-Claro 2016). Developmental instability occurs Stokes 2006; Peeters et al. 2007). Considering the structural in plants as a response to a given stressing factor, such complexity, we assumed that plants in sunny sites would as pollution, radiation, nutrient deficiency, light/shade develop better than their shaded counterparts (Gulmon & conditions, herbivory and parasitism, among others (Kozlov Chu 1981); above-ground plant parts would show increased et al. 1996; Møller & Shykoff 1999; Cuevas-Reyes et al. performance, including phenology intensity, and hence, a 2011; Alves-Silva 2012; Santos et al. 2013). Plants display high structural complexity. Regarding the potential toxicity developmental instability by increasing the difference of aluminium rich soils, we expected to find higher levels of between leaf sides, and this feature can be statistically leaf toughness and reduced structural complexity in plants assessed with fluctuating asymmetry (FA) analysis. FA is from the rupestrian field. based on the deviations from perfect symmetry in bilaterally symmetrical leaves (Cowart & Graham 1999; Cornelissen Materials and methods & Stiling 2005). Under non-stressed conditions, leaf sides should exhibit no difference between the right and left sides. However, stressed environments tend to increase Study Area leaf side differences, causing increased FA (Martel et al. 1999). Usually, high FA values are evidence of high stress We conducted this study at the Caldas Novas State (reviewed by Møller & Shykoff 1999). In the case of plants Park (Parque Estadual da Serra de Caldas Novas, PESCAN, with widespread occurrence, it has been shown that sun/ 17°47’13.0”S - 48°40’12.0”W). The park has an elliptical shade conditions may provoke developmental instability shape with approximately 123 km² of area. Its top has a (Puerta-Pinero et al. 2008; Alves-Silva 2012; Miljković 2012; large plateau, with slopes at its sides that form natural walls Alves-Silva & Del-Claro 2016) and decrease plant fitness and the ridge of the foot is surrounded by farms and urban (Venâncio et al. 2016b). Furthermore, abiotic factors allied allotment. The park vegetation is predominantlysensu to FA measures are fundamental in population biology stricto cerrado, but cerradão, campo sujo, campo rupestre studies, as they allow us to understand adaptations and (rupestrian grassland) and seasonal semi-deciduous forests coadaptations in population ecology (Graham et al. 2010). are also very frequent phytophysiognomies (Oliveira-Filho In this study, we aimed to investigate whether leaf & Ratter 2002; PESCAN 2015). area, herbivory, toughness, FA, structural complexity Two vegetation types were studied in this work. The first intensity and the number of inflorescences are influenced was a plateau with a sensu stricto cerrado phytophysiognomy, by phytophysiognomy – typical cerrado or rupestrian about 990 m in altitude, presenting mainly a red-yellow oxisol. field – and/or microhabitat conditions – shade or sun. The second site was a rupestrian field that occurs at the lower Acta Botanica Brasilica - 31(2): 286-294. April-June 2017 287 Diagramação e XML SciELO Publishing