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

Abstract

The degree of connection between leaf gas exchange and leaf water potential, and the autonomy of these variables in relation to meteorological conditions were determined in three cultivars of Coffea arabica during clear and cloudy days. High values of vapor pressure deficit, air temperature and photosynthetic photon flux density resulted in low leaf autonomy during a clear day, irrespective the degree of connection among leaf physiological variables. Tight synchronization between physiological and meteorological variables was considered one important cause of net photosynthesis (P N ) decreasing during a clear day. In contrast, diurnal P N was around three times higher on a cloudy day, when all cultivars presented high autonomy. Principal component analyses corroborated autonomy results revealing unambiguous opposition between leaf physiological and meteorological vectors, besides less leaf physiological variability throughout the clear day. Despite these general responses during clear and cloudy days, there were significant differences among studied cultivars. Leaf autonomy was an important reference to evaluate C. arabica under environmental stress and should be taken into account when selecting cultivars under field conditions. Key words: Coffea canephora, connectance degree, daily net photosynthesis, system analysis, water stress Autonomia e modulação da rede da fotossíntese e das relações hídricas de Coffea arabica em condições de campo: O grau de conexão entre as trocas gasosas e o potencial hídrico foliar e a autonomia dessas variáveis em relação às condições meteorológicas foram determinados em Coffea arabica, ao longo de dias claros e nublados. Os valores elevados do déficit de pressão de vapor, da temperatura do ar e da densidade do fluxo de fótons fotossinteticamente ativos resultaram em reduzida autonomia no dia claro, independentemente do grau de conexão entre as variáveis fisiológicas foliares. A forte sincronização entre a fisiologia da folha e as variáveis meteorológicas foi considerada uma importante causa da diminuição da fotossíntese líquida (P N ) no dia claro. Por outro lado, o valor de P N foi cerca de três vezes maior no dia nublado, quando todos os cultivares apresentaram maior autonomia. A análise de componentes principais corroborou os resultados de autonomia, revelando uma clara oposição entre os vetores fisiológicos e meteorológicos, além de uma menor variabilidade das características fisiológicas da folha ao longo do dia claro. Apesar dessas respostas gerais, ocorreram diferenças significativas entre as cultivares nos dias claro e nublado. A autonomia da folha foi uma importante referência para avaliar o comportamento de C. arabica sob estresse e deve ser levada em consideração na seleção de cultivares sob condições de campo. Palavras-chave: análise sistêmica, Coffea canephora, estresse hídrico, grau de conectância, fotossíntese líquida diurna

The use of network analysis to uncover homeostatic responses of a drought-tolerant sugarcane cultivar under severe water deficit and phosphorus supply

“…In short, it seems that strong links may enhance system stability in settings where high control is needed, whereas weak links seems to promote stability when little control is needed and a sudden perturbation of elevated magnitude is likely ). Previous studies dealing with network analysis to uncover systemic changes in the physiological behavior of plants have found a consistent pattern of network modulation in plants under constraining conditions (Camargo-Bortolin et al 2008;Prado et al 2004;Souza et al 2005Souza et al , 2009, where changes in C g enable higher system stability.…”

Network Connectance Analysis as a Tool to Understand Homeostasis of Plants under Environmental Changes

“…The network analysis approach has been applied in plant physiological studies with cultivated species [ 1 , 9 , 14 , 15 , 16 ] and ecophysiological studies of tropical trees [ 2 , 11 , 17 ]. In general, such an approach is based on correlations among the physiological parameters, is very simple, and consumes little time.…”

GRAFTING FOR IMPROVING NET PHOTOSYNTHESIS OF COFFEA ARABICA IN FIELD IN SOUTHEAST OF BRAZIL

“…Coffea arabica came originally from Ethiopia, where it grows naturally in shade (Marin et al ., 2005). In Brazil, C. arabica is cultivated mainly in open areas to increase grain production (DaMatta, 2004), but full sun irradiance in open field areas has been related to high leaf temperature, stomatal pore narrowing and decrease in net photosynthesis (Barros et al ., 1997; Camargo-Bortolin et al ., 2008; Ronquim et al ., 2006). On the other hand, sun leaves of C. arabica have shown high tolerance to excessive irradiance (Chaves et al ., 2007) and the ability to prevent photoinhibition of photosynthesis (Araujo et al ., 2008).…”

“…The difference between potential and actual diurnal net photosynthesis is an estimate of CO 2 that was not assimilated as a result of environmental and plant impediments to the photosynthetic process (Kikuzawa et al ., 2004; Ronquim et al ., 2006). Therefore, the difference between actual and potential diurnal net photosynthesis strongly depends on the intensity and the extension of midday depression (Camargo-Bortolin et al ., 2008).…”