Contributions of diffusional limitation, photoinhibition and photorespiration to midday depression of photosynthesis in Arisaema heterophyllum in natural high light

• DOI: 10.1046/j.1365-3040.2000.00547.x
• Publication Date: 2003-03-12T16:22:26Z
• Authors: Hiroyuki Muraoka; Yanhong Tang; Ichiro Terashima; Hiroshi Koizumi; Izumi Washitani
• Keywords: Photoinhibition; Photorespiration; Stomatal Conductance; Photosynthetically active radiation

ABSTRACT Diurnal changes in photosynthetic gas exchange and chlorophyll fluorescence were measured under full sunlight to reveal diffusional non‐diffusional limitations diurnal assimilation leaves of Arisaema heterophyllum Blume plants grown either a riparian forest understorey (shade leaves) or an adjacent deforested open site (sun leaves). Midday depressions rate ( A ) leaf conductance water vapour remarkably deeper shade than sun leaves. To evaluate the (i.e. stomatal internal) limitation assimilation, we used index [1– / 350 ], which is at chloroplast CO 2 concentration μ mol − 1 . was estimated from electron transport J T ), determined fluorometrically, specificity factor Rubisco S by techniques. In saturating light, obtained after ‘peak’ 70% greater that before ‘peak’, but leaves, it only 20% greater. The photochemical efficiency photosystem II Δ F m ′ thus considerably lower especially ‘peak’. not photosynthetically active photon flux density (PPFD) > 500 s depended positively on throughout day. Electron flows carboxylation oxygenation O RuBP ratio significantly higher little difference found Photorespiratory efflux absence atmospheric about three times We attribute midday depression increased photorespiration caused closure, severe photoinhibition. Thus, for capacities non‐photochemical quenching are essential avoid photoinhibitory damage tolerate high temperatures stress excess light. content has been recognized as raising capacity, also contributes increase capacity photorespiration.