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Growth and maintenance respiration for individual plants in hierarchically structured canopies of Medicago sativa and Helianthus annuus : the contribution of current and old assimilates
Author(s) -
Lötscher Markus,
Klumpp Katja,
Schnyder Hans
Publication year - 2004
Publication title -
new phytologist
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 3.742
H-Index - 244
eISSN - 1469-8137
pISSN - 0028-646X
DOI - 10.1111/j.1469-8137.2004.01170.x
Subject(s) - medicago sativa , helianthus annuus , respiration , shoot , botany , biology , relative growth rate , respiration rate , growth rate , horticulture , sunflower , agronomy , mathematics , geometry
Summary• Respiratory costs of Medicago sativa and Helianthus annuus individuals growing in hierarchically structured stands in a controlled environment were analysed with regard to the daily rate of carbon (C) assimilation. • Net assimilation of new C ( A n , g C d −1 ) and respiration rates of new ( R new , g C d −1 ) and old C ( R old , g C d −1 ) were assessed by 13 CO 2 labelling and gas exchange measurements. • Specific respiration rate of old C ( r old , g C g −1 C d −1 ) decreased exponentially with increasing shoot biomass, but was not affected by the instantaneous relative growth rate (Δ w i ). The growth coefficient g ( R new : A n ) was c . 0.32. In the most severely shaded subordinate plants, g was < 0.2, but low g stimulated r old . The contribution of R new to total respiraton ( f R, new ) and the carbon use efficiency CUE (1 – R /( A n + R new )) were c . 0.68 and 0.62 for Δ w i > 0.1, respectively. For Δ w i < 0.1, f R, new and CUE decreased with decreasing Δ w i in both dominant and subordinate plants. • The results suggest that R old was closely related to maintenance, whereas R new was primarily involved in growth.