A1 Refereed original research article in a scientific journal
COMBINED EFFECTS OF PARTIAL DEFOLIATION AND NUTRIENT AVAILABILITY ON CLONED BETULA-PENDULA SAPLINGS .2. CHANGES IN NET PHOTOSYNTHESIS AND RELATED BIOCHEMICAL-PROPERTIES
Authors: OVASKA J, RUUSKA S, RINTAMAKI E, VAPAAVUORI E
Publisher: OXFORD UNIV PRESS UNITED KINGDOM
Publication year: 1993
Journal: Journal of Experimental Botany
Journal name in source: JOURNAL OF EXPERIMENTAL BOTANY
Journal acronym: J EXP BOT
Volume: 44
Issue: 265
First page : 1395
Last page: 1402
Number of pages: 8
ISSN: 0022-0957
DOI: https://doi.org/10.1093/jxb/44.8.1395
Abstract
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.
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.
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