Document Detail


Chloroplast Biogenesis: XX. Accumulation of Porphyrin and Phorbin Pigments in Cucumber Cotyledons during Photoperiodic Greening.
MedLine Citation:
PMID:  16660176     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Abstract/OtherAbstract:
A study of greening in cucumber (Cucumis sativus L.) cotyledons grown under a light (14-hour) dark (10-hour) photoperiodic regime was undertaken. The pools of protoporphyrin IX, Mg-protoporphyrin IX monoester, protochlorophyllide, and protochlorophyllide ester were determined spectrofluorometrically. Chlorophyll a and b were monitored spectrophotometrically. Pigments were extracted during the 3rd hour of each light period and at the end of each subsequent dark period during the first seven growth cycles. Protoporphyrin IX did not accumulate during greening. Mg-protoporphyrin IX monoester and longer wavelength metalloporphyrins accumulated during the light cycles and disappeared in the dark. Their disappearance was accompanied by the accumulation of protochlorophyll. Higher levels of protochlorophyll were observed in the dark than in the light, and the greatest accumulation occurred during the third and fourth dark cycles. Protochlorophyllide was present in 3- to 10-fold excess over protochlorophyllide ester; it was detectable during the period of net chlorophyll accumulation as well as afterward. In contrast, protochlorophyllide ester was observable only during the first four photoperiodic cycles, suggesting that it was a metabolic intermediate only during the early stages of chlorophyll accumulation. Between the third and fourth growth cycles, a rapid increase in area and fresh weight per cotyledon began. This was accompanied by a 250-fold increase in the level of chlorophyll a + b during the three subsequent growth cycles. No lag period in the accumulation of chlorophyll b was observed, and at all stages of greening, the chlorophyll a/b ratio was approximately 3.
Authors:
C E Cohen; M B Bazzaz; S H Fullett; C A Rebeiz
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Plant physiology     Volume:  60     ISSN:  0032-0889     ISO Abbreviation:  Plant Physiol.     Publication Date:  1977 Nov 
Date Detail:
Created Date:  2010-06-29     Completed Date:  2010-06-29     Revised Date:  2010-09-15    
Medline Journal Info:
Nlm Unique ID:  0401224     Medline TA:  Plant Physiol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  743-6     Citation Subset:  -    
Affiliation:
Department of Horticulture, University of Illinois, Urbana, Illinois 61801.
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