Functional leaf traits of understory species: strategies to different disturbance severities / Traços funcionais foliares de espécies de sub-bosque: estratégias às diferentes intensidades de perturbação

The specific leaf area (SLA) has been related to environmental disturbances, showing a positive correlation between the disturbances intensities and SLA in a plant community. These studies, however, assessed the responses of plant community as a whole, neglecting species attributes, such as the position in the vertical stratum of forests. Considering the importance of SLA to understand forest ecological processes, this study aimed to determine the influence of the disturbance regime on the SLA of understory species, considering that, unlike for communities as a whole, an increase in the disturbance intensity implies a decrease in SLA of understory species. This study was conducted in nine understories of seasonal forests in Brazil. The most abundant species were selected and their SLA were evaluated. The variability of SLA among populations in different forests was analyzed by Student’s t-tests. The SLA of the understories (SLAU) was also compared by an adaptation of the Community-weighted mean index. The comparison of species SLA showed significant differences among the populations of understories under different disturbance regime, showing a decrease in SLA with an increase in the disturbance intensity. Similar results were found for the SLA of understories communities (SLAU), corroborating our hypothesis. The correlation between a reduction in species SLA and in SLA of understory with an increase in disturbance intensity, contradicted the trend observed in the literature for the community as a whole. This study highlights the importance of the evaluation of SLA in understories, as an indicator of the successional stage of communities.

A área foliar específica (SLA) tem sido relacionada a distúrbios ambientais, apresentando uma correlação positiva entre a intensidade de perturbação e a SLA da comunidade vegetal. Estes estudos, no entanto, avaliaram as respostas da comunidade vegetal como um todo, negligenciando os atributos por espécies, tais como a posição vertical no estrato florestal. Considerando a importância da SLA para entender os processos ecológicos das florestas, este estudo teve como objetivo determinar a influência do regime de perturbação na SLA de espécies de sub-bosque, cuja hipótese é que, ao contrário de comunidades como um todo, um aumento na intensidade de perturbação implica na diminuição da SLA de espécies de sub-bosque. Este estudo foi realizado em nove sub-bosque de florestas estacionais no Brasil. As espécies mais abundantes foram selecionados e suas SLA foram avaliadas. A variabilidade de SLA entre as populações em diferentes florestas foi analisada pelo teste t de Student. O SLA dos sub-bosque (SLAu) também foi comparado por uma adaptação do índice de média ponderada da comunidade. A comparação de SLA das espécies mostraram diferenças significativas entre as populações de sub-bosque sob um regime de distúrbios diferentes, mostrando um decréscimo na SLA com um aumento na intensidade de perturbação. Resultados semelhantes foram encontrados para o SLA dos sub-bosque (SLAu), corroborando nossa hipótese. A correlação entre a redução no SLA espécies e SLA do sub-bosque com um aumento na intensidade de perturbação contradiz a tendência observada na literatura para a comunidade como um todo. Este estudo destaca a importância da avaliação de SLA em sub-bosque, como um indicador do estágio sucessional das comunidades.

Variabilidad ambiental y respuestas fisiológicas de Polylepis cuadrijuga (Rosaceae) en un ambiente fragmentado en el Páramo de la Rusia (Colombia) / Environmental variability and physiological responses from Polylepis cuadrijuga (Rosaceae) in a fragmented environment in the Páramo de la Rusia (Colombia)

Polylepis cuadrijuga is an endemic woody species from the Colombian Eastern range, being the only tree species with capacity to live on mountainous environments beyond 4 000m of altitude. Grazing and agriculture have transformed at least 30% of the Guantiva-La Rusia region, turning continuous extensions of high Andean forest in a fragmented landscape, and P. cuadrijuga remnants have become smaller and more isolated. The aim of this study was to establish the environmental differences between a matrix of grazing pastures and the interior of fragments, to evaluate the physiological responses of P. cuadrijuga and determining the edge effect. Air temperature and humidity, soil water holding capacity and photosynthetic active radiation, were measured along two 50X2m transects from the matrix toward the center of fragment. Six trees inside the transects were chosen in each one of three sites (matrix, edge and interior) to measure the index chlorophyll content and to sample leaves to assess the leaf area, leaf biomass, specific leaf area, anatomy, health condition and pubescence. Results showed significantly differences between the matrix and the interior and intermediate conditions in the edge. Radiation, temperature and air desiccation were higher in the matrix than in the interior, submitting P. cuadrijuga trees to a stressing environment, where they presented stratification of epidermis and palisade parenchyma, and a higher leaf area, leaf thickness, chlorophyll content and pubescence than in the interior of fragments. All these physiological traits allow avoiding the photoxidation and damages by freezing or desiccation to which trees are exposed in a grazing pasture matrix. Nevertheless, there was a higher frequency of healthy leaves in the interior of fragments, showing that high irradiations and extreme air temperature and humidity reach adversely affect to P. cuadrijuga. Individuals in the edge had ecophysiological traits similar to the matrix ones, which confirm an edge effect that could penetrate 17m inside the fragments. We conclude that P. cuadrijuga is a plastic species, able to overcome the stress conditions from anthropogenic transformations, species able to be used in high Andean forest restoration programs.

Polylepis cuadrijuga es una especie leñosa endémica de la cordillera oriental de Colombia, donde la agricultura y el pastoreo han generado la fragmentación de sus bosques. Para determinar si existe un efecto borde en fragmentos ubicados en el Páramo de la Rusia, se establecieron diferencias ambientales y se evaluó las respuestas ecofisiológicas de P. cuadrijuga entre matriz de pastura, borde e interior de los fragmentos, a través de la medición de temperatura ambiental, humedad relativa, capacidad de retención de agua del suelo y radiación fotosintéticamente activa, a lo largo de dos transectos de 50m desde la matriz hacia el interior. En cada sitio se escogieron seis árboles para evaluar el contenido de clorofila, área foliar, biomasa foliar, área foliar específica, anatomía foliar, sanidad y pubescencia. En matriz fue mayor la temperatura y la radiación, condiciones relacionadas con la disminución del AFE y el aumento del contenido de clorofilas, evidenciado por la presencia de un parénquima en empalizada biestratificado. Características ecofisiológicas similares a las expuestas en borde, confirman un efecto de borde que podría penetra unos 17m en el interior de los fragmentos. Se concluye que P. cuadrijuga es una especie plástica, capaz de enfrentar condiciones de estrés generadas por actividades antropogénicas.

Supplemental UV-B radiation induced changes in growth, pigments and antioxidant pool of bean (Dolichos lablab) under field conditions.

Present study is conducted to evaluate the response of bean (Dolichos lablab cv . pusa early prolific) plants to supplemental UV-B (sUV-B: 280-315 nm: 7.2 kJ m-2 d-1) radiation. UV-B caused alteration in biomass translocation pattern with more retention of biomass in below ground parts leading to an increment in root shoot ratio. Specific leaf area (SLA) which is the measure of leaf thinness, increased in plants under sUV-B exposure by 95.7 and 82.3% after 15 and 30 days after germination. Photosynthetic machinery of bean plants was the potential target of UV-B as photosynthetic rate was decreased by 88.6 % at 30 days after germination. sUV-B lead to the formation of reactive oxygen species thus generating oxidative stress. Stimulation of antioxidant defense system (enzymatic and non-enzymatic) was observed due to sUV-B radiation. Phenolic content decreased (34.7 and 18.6%) but protein showed varied response, increased initially (34%) thereafter declined (10.2%) under sUV-B radiation.

Crescimento de plantas de Salvia officinalis sob ação de reguladores de crescimento vegetal / Growth of Salvia officinalis plants under action of plant growth regulators

O objetivo deste trabalho foi estimar os parâmetros da análise de crescimento em função de diferentes reguladores vegetais aplicados na parte aérea de plantas de Salvia officinalis L. Para tanto,o experimento foi instalado em casa de vegetação do Departamento de Botânica, Instituto de Biociências, da Universidade Estadual Paulista, Botucatu, SP. Os tratamentos consistiram na pulverização da solução de 100mg L-1 de ácido giberélico (GA3); 100mg L-1 de benzilaminopurina (BAP); 100mg L-1 de ácido 2-cloroetil-fosfônico (ethephon); Stimulate® a 2 por cento (90mg L-1 de cinetina, 50mg L-1 de ácido giberélico e 50mg L-1 de ácido indolilbutírico) e água (testemunha). As aplicações foram realizadas em três épocas, aos 15, 25 e 35 dias após o transplante (d.a.t.) e o crescimento foi avaliado em cinco épocas de coletas a intervalos de 21 dias, sendo a primeira realizada aos 47 (d.a.t.). Foram determinados os parâmetros fisiológicos da análise de crescimento: razão de área foliar (RAF), área foliar específica (AFE), taxa assimilatória líquida (TAL) e taxa de crescimento relativo (TCR). Os resultados mostram que os reguladores de crescimento vegetal influenciaram os parâmetros fisiológicos da análise de crescimento. As plantas tratadas com BAP apresentaram maiores valores de RAF aos 47 d.a.t., já as plantas tratadas com GA3, a TAL apresentou aumento até o 131 d.a.t. A TCR é decrescente para todos os tratamentos com reguladores de crescimento vegetal testados e a testemunha.

The objective of this study was to estimate the effects of different plant regulators on the index growth analysis application of sage plants. An experiment was conducted in a greenhouse with controlled temperature and relative humidity, at the Departmento de Botânica, Instituto de Biociências, Universidade Estadual Paulista, UNESP, Botucatu, SP, Brazil. The experimental design was completely randomized, with five treatments containing three replicates. Treatments consisted of the spraying of the solution of 100mg L-1 of gibberellic acid (GA3); 100mg L-1 of benzylaminopurine (BAP); 100mg L-1 of 2-chloroethyl phosphonic acid (ethephon); Stimulate® at 2 percent (90mg L-1 of kinetin, 50mg L-1 of gibberellic acid and 50mg L-1 of indolylbutyric acid) and water (control). Applications of plant growth regulators were performed in 3 times, at 15, 25, and 35 days after transplanting, and growth was evaluated in five successive harvests at 21-day intervals, performed at 47, 68, 89, 110, and 131 days after transplanting. The following growth index were determined: leaf area ratio (LAR), specific leaf area (SLA), net assimilation rate (NAR), and relative growth rate (RGR). These results suggest that the plant growth regulators influence the index growth analysis. The plants treated with BAP presented increase values of LAR to the 47 days after transplanting. The plants treated with GA3 to NAR presented increase until the 131 days after transplanting. The RGR is decreasing for all the treatments with vegetal regulators tested and the control.

Fotosíntesis en tres poblaciones altitudinales de la planta andina Espeletia schultzii (Compositae) / Photosynthesis in three altitudinal populations of the Andean plant Espeletia schultzii (Compositae)

Photosynthesis was compared in three altitudinal populations of Espeletia schultzii: 3,100, 3,550 and 4,200 masl. The measured parameters were Rubisco activity (EC 4.1.139), chlorophyll, soluble protein and soluble sugars contents, and specific leaf area (SLA). The 4,200 m population had a higher Rubisco activity (at 4 degrees C) followed by those at 3,550 m and 3,100 m. There were no significant differences between populations at 3,100 m and 3,550 m (ANOVA), but their activities were different from those of the 4,200 m population. Chlorophyll a content decreased slightly with elevation, while chlorophyll b was constant; therefore, the Ra/b ratio decreased with elevation, but not significantly. The leaf soluble sugars content increased along the altitudinal gradient. Leaf protein content did not differ. The SLA decreased with altitude. The increase in Rubisco activity might reflect higher enzyme activation and not higher enzyme protein. The increase in soluble sugars is probably associated to Rubisco activity. Three out of the five measured parameters revealed differences with altitude, suggesting a compromise between a higher metabolic activity and a smaller cellular volume.

Se establece una comparación de algunos parámetros fotosintéticos: actividad Rubisco (Ribulosa 1, 5-bis-fosfato carboxilasa EC 4.1.1.39) contenidos de clorofilas, azúcares solubles totales y proteínas solubles totales y área foliar específica (AFE), en tres poblaciones altitudinales de Espeletia schultzii ubicadas a 3 100, 3 550 y 4 200 msnm. De acuerdo con el análisis de varianza la población a 4 200 m presentó una actividad Rubisco significativamente mayor que las otras dos, en cuyos casos los valores no fueron diferentes. Los contenidos de clorofila a presentan una leve tendencia a la disminución con la altura; mientras que la clorofila b se mantiene constante, razón por la cual la relación a/b (R a/b) disminuye con la elevación, aunque, las diferencias no son significativas. El contenido de azúcares en cada una de las poblaciones estudiadas (gm-2), aumenta con la elevación; las diferencias entre las poblaciones son significativas. Con relación al contenido de proteínas, no existen diferencias entre las poblaciones estudiadas. El área foliar específica (AFE) disminuye significativamente con la altura. Es probable que el incremento en la actividad Rubisco sea producido por una mayor activación de la enzima y no por el mayor contenido de proteína. Los azúcares solubles presentan incremento significativo, este hecho es probable que se encuentre asociado con la actividad Rubisco. De los cinco parámetros fotosintéticos medidos, tres presentan diferencias significativas asociadas con la altitud. Esto representa un compromiso entre una mayor actividad metabólica mantenida en un menor volumen celular.