Document Detail

Increased photosynthesis following partial defoliation of field-grown Eucalyptus globulus seedlings is not caused by increased leaf nitrogen.
MedLine Citation:
PMID:  17669738     Owner:  NLM     Status:  MEDLINE    
Increased photosynthetic rates following partial defoliation may arise from changes in leaf biochemistry, water relations or nutrient status. Twelve-month-old field-grown Eucalyptus globulus Labill. seedlings were pruned from below to reduce the green crown depth by 50 (D50) or 70% (D70). Photosynthetic responses to light and CO2 concentration were examined before and one, three and five weeks after partial defoliation. One week after defoliation, photosynthetic rates were greater in seedlings in the D50 (21 micromol m(-2) s(-1)) and D70 (23 micromol m(-2) s(-1)) treatments than in control seedlings (15 micromol m(-2) s(-1)); however, there was little difference in photosynthetic rates between partially defoliated seedlings and control seedlings after 5 weeks. An analysis of the sensitivity of photosynthesis to biochemical parameters revealed that the transient increase in photosynthetic rate in response to partial defoliation was largely a function of the maximum rate of carboxylation (85-87%) and the maximum rate of RuBP regeneration (55-60%) rather than stomatal conductance (12-13%). Nitrogen increased in leaves following partial defoliation (increases of 0.6 and 1.2 g m(-2) for D50 and D70, respectively), but was accumulated in a non-photosynthetic form (i.e., there was no increase in nitrogen concentration of Rubisco or chlorophyll). Increased photosynthetic rates immediately following partial defoliation were primarily a result of increased activity rather than amount of photosynthetic machinery. There was no evidence that phosphorus was responsible for the increase in photosynthetic rates after partial defoliation.
Tarryn L Turnbull; Mark A Adams; Charles R Warren
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Publication Detail:
Type:  Journal Article; Research Support, Non-U.S. Gov't    
Journal Detail:
Title:  Tree physiology     Volume:  27     ISSN:  0829-318X     ISO Abbreviation:  Tree Physiol.     Publication Date:  2007 Oct 
Date Detail:
Created Date:  2007-08-02     Completed Date:  2007-12-14     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  100955338     Medline TA:  Tree Physiol     Country:  Canada    
Other Details:
Languages:  eng     Pagination:  1481-92     Citation Subset:  IM    
Ecology and Ecosystem Science, School of Biological Earth and Environmental Sciences, University of New South Wales, NSW 2052, Australia.
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MeSH Terms
Chlorophyll / metabolism
Eucalyptus / metabolism*
Nitrogen / metabolism*
Phosphorus / metabolism
Photosynthesis / physiology*
Plant Leaves / metabolism*
Ribulose-Bisphosphate Carboxylase / metabolism
Seedling / metabolism*
Reg. No./Substance:
1406-65-1/Chlorophyll; 7723-14-0/Phosphorus; 7727-37-9/Nitrogen; EC Carboxylase

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine

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