Photosynthetic responses of young cashew plants to varying environmental conditions

Pesquisa Agropecuária Brasileira

Rogéria Pereira De Souza²  Rafael Vasconcelos Ribeiro²  Eduardo Caruso Machado²  Ricardo Ferraz De Oliveira¹  Joaquim Albenísio Gomes Da Silveira¹ 

[1] ,Instituto Agronômico Centro de Pesquisa e Desenvolvimento em Ecofisiologia e Biofísica Campinas SP ,Brazil

关键词: Anacardium occidentale;    gas exchange;    chlorophyll fluorescence;    temperature;    vapor-pressure deficit;    Anacardium occidentale;    trocas gasosas;    fluorescência da clorofila;    temperatura;    déficit da pressão de vapor;   

DOI  :  10.1590/S0100-204X2005000800002

来源: SciELO

【 摘 要 】

The aim of this study was to characterize gas exchange responses of young cashew plants to varying photosynthetic photon flux density (PPFD), temperature, vapor-pressure deficit (VPD), and intercellular CO2 concentration (Ci), under controlled conditions. Daily courses of gas exchange and chlorophyll a fluorescence parameters were measured under natural conditions. Maximum CO2 assimilation rates, under optimal controlled conditions, were about 13 mmol m-2 s-1 , with light saturation around 1,000 mmol m-2 s-1. Leaf temperatures between 25ºC and 35ºC were optimal for photosynthesis. Stomata showed sensitivity to CO2, and a closing response with increasing Ci. Increasing VPD had a small effect on CO2 assimilation rates, with a small decrease above 2.5 kPa. Stomata, however, were strongly affected by VPD, exhibiting gradual closure above 1.5 kPa. The reduced stomatal conductances at high VPD were efficient in restricting water losses by transpiration, demonstrating the species adaptability to dry environments. Under natural irradiance, CO2 assimilation rates were saturated in early morning, following thereafter the PPFD changes. Transient Fv/Fm decreases were registered around 11h, indicating the occurrence of photoinhibition. Decreases of excitation capture efficiency, decreases of effective quantum yield of photosystem II, and increases in non-photochemical quenching were consistent with the occurrence of photoprotection under excessive irradiance levels.

【 授权许可】

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