Network connectance and autonomy analyses of the photosynthetic apparatus in tropical tree species from different successional groups under contrasting irradiance conditions

Abstract

-(Network connectance and autonomy analyses of the photosynthetic apparatus in tropical tree species from different successional groups under contrasting irradiance conditions). Biological systems are complex dynamical systems whose relationships with environment have strong implications on their regulation and survival. From the interactions between plant and environment can emerge a quite complex network of plant responses rarely observed through classical analytical approaches. The objective of this current study was to test the hypothesis that photosynthetic responses of different tree species to increasing irradiance are related to changes in network connectances of gas exchange and photochemical apparatus, and alterations in plant autonomy in relation to the environment. The heat dissipative capacity through daily changes in leaf temperature was also evaluated. It indicated that the early successional species (Citharexylum myrianthum Cham. and Rhamnidium elaeocarpum Reiss.) were more efficient as dissipative structures than the late successional one (Cariniana legalis (Mart.) Kuntze), suggesting that the parameter ∆T (T ºC air -T ºC leaf ) could be a simple tool in order to help the classification of successional classes of tropical trees. Our results indicated a pattern of network responses and autonomy changes under high irradiance. Considering the maintenance of daily CO 2 assimilation, the tolerant species (C. myrianthum and R. elaeocarpum) to high irradiance trended to maintain stable the level of gas exchange network connectance and to increase the autonomy in relation to the environment. On the other hand, the late successional species (C. legalis) trended to lose autonomy, decreasing the network connectance of gas exchange. All species showed lower autonomy and higher network connectance of the photochemical apparatus under high irradiance.Key words -dissipative structures, functional groups, high irradiance, network connectance, photosynthesis RESUMO -(Análises de conectância da rede e autonomia do aparato fotossintético em espécies tropicais arbóreas de diferentes grupos sucessionais sob condições de irradiância contrastantes). Sistemas biológicos são sistemas dinâmicos complexos cujas relações com o ambiente apresentam importantes implicações sobre seus processos de regulação e sobrevivência. A partir destas interações pode emergir uma complexa rede de respostas que raramente são observadas pelas abordagens analíticas clássicas. Desta forma, o objetivo deste estudo foi testar a hipótese de que as respostas fotossintéticas de diferentes espécies arbóreas ao aumento da irradiância estão relacionadas às mudanças na conectância das redes de trocas gasosas e do aparato fotoquímico, assim como mudanças no grau de autonomia entre planta e ambiente. A capacidade de dissipação térmica avaliada por mudanças da temperatura foliar ao longo do dia também foi analisada, indicando que as espécies iniciais da sucessão (Citharexylum myrianthum Cham. e Rhamnidium elaeocarpum Reiss.) foram mais eficientes...

Photosynthetic performance and anatomical adaptations in Byrsonima sericea DC. under contrasting light conditions in a remnant of the Atlantic forest

“…Usually in the dry season there is a reduction in photosynthetic assimilation and transpiration as a consequence of reduced stomatal conductance . Many ecophysiological studies involving sun and shade plants have reported comparisons between plants of different successional stages (Souza et al, 2005;Silvestrini et al, 2007;Portes et al, 2008) or of the same species (Nobel, 1976;Dias et al, 2007;Li et al, 2009;Dai et al, 2009). Although studies relating several successional stages are extremely important for understanding the function of the species that integrate an ecosystem, studies involving only one successional group in different environmental conditions, after human impacts, may help to understand the effect of forest fragmentation on the adaptive responses of these plants.…”

Autonomy and network modulation of photosynthesis and water relations of Coffea arabica in the field

“…Above the physiological network there are meteorological variables related to the strength of connection between paired physiological variables during the course of the day. Plant autonomy (At) was obtained through the correlation between leaf physiological variables and the meteorological variables Souza et al, 2005). Therefore, At was determined on clear and cloudy days as the average of zvalues between two data sets: P N , g s , C i /C e , E, ITE, Y w , T leaf , and PPFD, T air , VPD air .…”

“…Therefore, At was determined on clear and cloudy days as the average of zvalues between two data sets: P N , g s , C i /C e , E, ITE, Y w , T leaf , and PPFD, T air , VPD air . Thus, lower connectance between physiological-meteorological variables means a higher degree of autonomy (Souza et al, 2005).…”

“…The interaction among leaf physiological variables and their relationship with the environment can be evaluated by autonomy and global connectance (Souza et al, 2005). Autonomy (At) depicts how much physiological variables change independently of the environment.…”

“…Global connectance (Cg) represents the degree that network components are connected to each other. It is determined through the correlation between network components with a close physiological relationship (Amzallag, 2001;Souza et al, 2005). High Cg of a given network results in prompt response to environmental disturbances, but it facilitates the propagation of disturbance through the network.…”