Combined Effects of Partial Defoliation and Nutrient Availability on Cloned Betula pendula Saplings: II. CHANGES IN NET PHOTOSYNTHESIS AND RELATED BIOCHEMICAL PROPERTIES

The combined effects of partial defoliation and nutrient availability on net photosynthesis and related biochemical variables were studied in cloned Betula pendula Roth saplings. The saplings were randomly assigned to different nutrient levels (5, 1.5 and 0.5 mol N m-3) in aerated nutrient culture a...

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Bibliographic Details
Published in:Journal of experimental botany 1993-08, Vol.44 (265), p.1395-1402
Main Authors: Rintakmäki, E., OVASKA, JARI, RUUSKA, SARI, RINTAMÄKI, EEVI, VAPAAVUORI, ELINA
Format: Article
Language:English
Subjects:
Agronomy. Soil science and plant productions
Betula pendula
Biological and medical sciences
Defoliation
Fundamental and applied biological sciences. Psychology
Leaves
Metabolism
Nitrogen
Nutrient availability
Nutrient nutrient interactions
Nutrients
Nutrition
Photosynthesis
Photosynthesis, respiration. Anabolism, catabolism
Plant physiology and development
Saplings
Statistical significance
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Summary:The combined effects of partial defoliation and nutrient availability on net photosynthesis and related biochemical variables were studied in cloned Betula pendula Roth saplings. The saplings were randomly assigned to different nutrient levels (5, 1.5 and 0.5 mol N m-3) in aerated nutrient culture and to the following defoliation treatments: (1) control (no damage), (2) damage of the developing main stem leaves (half of the leaf lamina removed), and (3) removal of the developing main stem leaves (entire leaf lamina removed). The leaf immediately below the damaged area in the treated plants, and the corresponding leaf in the control plants, were selected for study. Net photosynthesis measurements and biochemical determinations were made 2, 8 and 14 d after assigning the treatments. At intermediate and low nutrient levels the final net photosynthetic capacity was significantly higher in the saplings with the topmost leaves removed than in the undamaged control saplings, indicating that the expression of compensatory photosynthesis after partial defoliation is not inhibited by nutrient deficiency. The photosynthetic enhancement was closely associated with the increased initial activity of ribulose 1,5-bisphosphate carboxylase/oxygenase (Rubisco). However, the increased activity of Rubisco was not exclusively the result of a higher amount of Rubisco. The expression of compensatory photosynthesis after partial defoliation in our study cannot unequivocally be attributed to an increased flow of nitrogen to the remaining leaves.
ISSN:0022-0957
1460-2431