Meteorological conditions, ozone concentration and leaf age affect gas exchange in Psidium guajava ‛Palumaʼ

Abstract

-(Meteorological conditions, ozone concentration, and leaf age affect gas exchange in Psidium guajava ‛Paluma'). This study aimed to investigate the importance of leaf age, meteorological conditions and ozone concentration (O 3 ) on gas exchange of Psidium guajava ‛Paluma'. Saplings were grown and exposed in standard conditions in the city of São Paulo, in six periods of three months with weekly measurements in young and mature leaves. Gas exchanges were higher in young leaves for almost the entire experiment. Mature leaves showed greater reduction in gas exchange. The multivariate analysis of biotic and abiotic variables indicated that vapor pressure deficit (VPD), O 3 concentration and radiation were the main variables associated with gas exchange decrease in young leaves. In mature leaves the influence of VPD is lower, but the temperature importance is higher. Moreover, the opposition between assimilation and O 3 is more evident in mature leaves, indicating their greater sensitivity to O 3 . Keywords: carbon assimilation, ozone phytotoxicity, stomatal conductance RESUMO -(Condições meteorológicas, concentração de ozônio e idade da folha afetam as trocas gasosas em Psidium guajava 'Paluma'). Este estudo teve como objetivo investigar a influência da idade da folha, das condições meteorológicas e da concentração do ozônio (O 3 ) nas trocas gasosas em Psidium guajava 'Paluma'. Plantas jovens foram cultivadas e expostas de modo padronizado na cidade de São Paulo, SP, em seis períodos de três meses, com medidas semanais em folhas jovens e maduras. As trocas gasosas foram mais altas nas folhas jovens durante quase todo o experimento. As folhas maduras apresentaram maior redução das trocas gasosas. A análise multivariada das variáveis bióticas e abióticas indicou que o déficit de pressão de vapor (DPV), a concentração de O 3 e a radiação foram as principais variáveis associadas à redução das trocas gasosas nas folhas jovens. Nas folhas maduras a influencia do DPV é menor, mas a da temperatura é maior. Por outro lado, a oposição entre assimilação e O 3 é mais evidente nas folhas maduras, indicando sua maior sensibilidade ao O 3 . Palavras-chave: assimilação de carbono, condutância estomática, fitotoxicidade do ozônio

Effects of ozone (O3) and ethylenediurea (EDU) on the ecological stoichiometry of a willow grown in a free-air exposure system

“…Decreased P content was also found in yellowish leaves, but not in non-injured or bronzing leaves, of European aspen exposed to 100 nmol O 3 mol -1 for two growing seasons (Matyssek et al, 1993). EOZ led also to alterations in the stoichiometry of Ni, (Bison et al, 2018;Craker and Starbuck, 1973;Moreno Pina et al, 2017;Shang et al, 2018;Shi et al, 2017;Uddling et al, 2006). The regulation of Cr may be a mechanism for maintaining carbon metabolism (Samantaray et al, 1998).…”

“…Younger or late leaves may be more resistant to O 3 than older, mature leaves (Li et al, 2017;Moreno Pina et al, 2017) as a result of adaptive responses which may take place at plant level. For example, relative to mature leaves, younger leaves may: emit greater concentrations of volatile organic compounds (Bison et al, 2018); take up less amount of O 3 (Craker and Starbuck, 1973); have greater carbon (C) assimilation rate and water use efficiency (Moreno Pina et al, 2017); and overall have greater efficiency in apoplastic O 3 detoxification as indicated by avoidance of accumulation of reactive oxygen species in the chloroplasts (Oksanen et al, 2005). Besides, shed leaves may be more affected than mature leaves as they experience O 3 pressure for longer time and the nutrient retranslocation may also be affected (Shang et al, 2018;Shi et al, 2017;Uddling et al, 2006).…”