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Influence of N form on growth photosynthesis of Phaseolus vulgaris L. plants
Author(s) -
Brück Holger,
Guo Shiwei
Publication year - 2006
Publication title -
journal of plant nutrition and soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.644
H-Index - 87
eISSN - 1522-2624
pISSN - 1436-8730
DOI - 10.1002/jpln.200520570
Subject(s) - phaseolus , photosynthesis , ammonium , carboxylation , chemistry , stomatal conductance , chlorophyll , nitrate , horticulture , botany , agronomy , biology , biochemistry , organic chemistry , catalysis
Many plant species are characterized by pronounced sensitivity to sole ammonium supply and exhibit growth depression and particularly reduced leaf growth rates. Stress symptoms under sole ammonium supply may be related to perturbation of photosynthetic processes, e.g. , low rates of net CO 2 assimilation, low quantum yield, reduced stomatal conductance, and carboxylation capacity. The results of three experiments with French bean plants supplied with an N concentration of 5 mM illustrate significantly lower dry mass and specific leaf area, reduced leaf expansion, and higher chlorophyll and N content of ammonium‐ compared to nitrate‐supplied plants. Light‐saturated rates of CO 2 assimilation (A max ) per unit leaf area were higher under ammonium compared to nitrate supply while no significant effects of N form on quantum yield and A max per unit leaf weight and chlorophyll were found. Maximal carboxylation (V cmax ) and electron‐transport (J Max ) rates were significantly higher under ammonium supply only in one of three experiments. V cmax was linearly related to total leaf N, the slope of the regression was similar with both N forms, the x‐axis intercept was significantly higher for ammonium‐ compared to nitrate‐supplied plants. The ratio V cmax : J Max was not affected by N form. It is concluded that ammonium supply had no negative effects on the operation of photosynthetic protein‐enzyme complexes.