EFFECTS OF BICARBONATE ION ON CHLOROPHYLL a FLUORESCENCE TRANSIENTS AND DELAYED LIGHT EMISSION FROM MAIZE CHLOROPLASTS
نویسنده
چکیده
Using high-intensity actinic light, the chlorophyll a fluorescence transient from HC0,-depleted chloroplasts shows a rapid initial rise (0 + 1) followed by a slow phase ( I + P). In the presence of HC0,-, the 0 -+ I rise is delayed but the I + P phase is much more rapid. Using lowintensity actinic light, the chlorophyll a fluorescence transient from 3-(3.4-dichlorophenyI)I , I dimethylurea (DCMU)-treated chloroplasts is delayed in the presence of HC0,-. Bicarbonate increases the amount of delayed light emission from chloroplasts given 10 s illumination with weak blue light (0.4 W/m2)). DCMU greatly increases the amount of delayed light seen in the presence of HC03under these conditions but decreases the amount seen in the absence of HCO,-. I t is suggested that HCO:3may somehow form or stabilize, in the dark, a number of reaction centers corresponding to the S , state in the model of B. Forbush, B. Kok and M. McGloin (Photochem. Phoiobiol. 14, 307-321, 1971).
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