Relation of CO2 exchange in needles of Austrian Black Pine (Pinus nigra subsp. nigricans var. austriaca) to age, chlorophyll content and reassimilation

E.A.uni, M.H.; Mousseau, M.

Photosynthetica 8(2): 78-86

1974


ISSN/ISBN: 0300-3604
Accession: 000480096

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Abstract
Laboratory studies showed that gaseous exchange in P. nigra seems to be closely correlated with needle structure. Photosynthetic activity during the life of needles shows a drop in winter, irrespective of the total chlorophyll content, which appears to be correlated with a chloroplast degradation as a result of low temperatures. This degradation becomes less and less reversible with age. The renewed activity during the growing season is due in part to an increase in the photoreceptor pigment content: a close quantitative relation was observed between the net photosynthetic rate and chlorophyll content, even at saturating irradiances. The relation between these two parameters varies, however, with needle age, unit chlorophyll efficiency diminishing with increasing age.