Photoinhibition and Zeaxanthin Formation in Intact Leaves

摘要: Comparative studies of chlorophyll a fluorescence, measured with pulse amplitude modulated fluorometer, and the pigment composition leaves, suggest specific role zeaxanthin, carotenoid formed in xanthophyll cycle, protecting photosynthetic apparatus against adverse effects excessive light. This conclusion is based on following findings: (a) exposure leaves Populus balsamifera, Hedera helix, Monstera deliciosa to excess excitation energy (high light, air; weak 2% O2, 0% CO2) led massive formation zeaxanthin decrease violaxanthin. Over wide range conditions, there was linear relationship between either variable, Fv, or maximum Fm, content leaves. (b) When exposed photoinhibitory light levels air, shade H. helix had higher capacity for formation, at expense β-carotene, than M. deliciosa. Changes fluorescence characteristics suggested that, predominant response high an increase rate nonradiative dissipation, whereas, deliciosa, damage photosystem II reaction centers prevailing effect. (c) Exposure sun leaf P. balsamifera increasing photon flux densities O2 CO2 resulted initially (matched by decreases violaxanthin) accompanied changes indicative increased dissipation. Above level which no further observed, indicated damage. (d) A obtained ratio variable Fv/Fm, determined technique room temperature, yield evolution, similar previous findings (O Bjorkman, B Demmig 1987 Planta 170: 489-504) 77 K photosynthesis.