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Development of photosystem-II activity during irradiance of etiolated Helianthus (Asteraceae) seedlings
- Source :
- American journal of botany. 86(8)
- Publication Year :
- 1999
-
Abstract
- Light-induced development of photosystem (PS)-II activity was followed during irradiance of etiolated Helianthus annuus (sunflower) cotyledons using chlorophyll a fluorescence. Cotyledons from seedlings grown in continuous darkness for 6 d were exposed to 100 μmol photons·m(-2)·s(-1) for time periods of 1, 3, 6, and 12 h. Associated with increased time of irradiance exposure were significant: (1) increases in concentration of PS II, (2) increases in quantum efficiency of PS II, (3) decreases in the ratio of PS-II quinone(B) (Q(B))-nonreducing centers to total PS-II centers (PS-II Q(B)-nonreducing centers + PS-II Q(B)-reducing centers), and (4) decreases in the ratio of slow PS-II Q(B)-reducing centers to total PS-II Q(B)-reducing centers (fast PS-II Q(B)-reducing centers + slow PS-II Q(B)-reducing centers). The results support the hypotheses that development of PS II involves assembly of complexes which initially cannot reduce Q(B) and that heterogeneous aspects of PS-II pools during chloroplast maturation may represent different developmental states.
Details
- ISSN :
- 00029122
- Volume :
- 86
- Issue :
- 8
- Database :
- OpenAIRE
- Journal :
- American journal of botany
- Accession number :
- edsair.pmid..........7edabe656e6b87482de74c6de08f4024