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Plant Physiology 93:1219-1225 (1990) © 1990 American Society of Plant Biologists Carbon Metabolism in Spinach Leaves as Affected by Leaf Age and Phosphorus and Sulfur Nutrition 1Institut für Botanik und Pharmazeutische Biologie, Julius-Maximilians-Universität Würzburg, Mittlerer Dallenbergweg 64, 8700 Würzburg, Federal Republic of Germany
Spinach (Spinacea oleracea) plants were grown either continuously on complete nutrient solutions or for 2 weeks on media deficient in phosphate or sulfate. To characterize leaf carbohydrate metabolism, levels of phosphorylated intermediates, activities of enzymes involved in photosynthetic carbon metabolism, contents of soluble and acid hydrolyzable sugars were measured in leaves differing in age and mineral status and related to leaf rates of photosynthesis and assimilate partitioning. Concentrations of metabolitesparticularly those which are preferentially compartmented in the cytosoldecreased from young to old leaves and were lowest in old phosphate starved leaves. Nutrient deficiency showed comparable effects on stromal and cytosolic intermediates. Whole leaf ATP to ADP ratios were dependent on the growth regime, but did not much change with leaf age. The assimilatory force increased in all leaves suffering from mineral deficiency; the assimilatory force was low when photosynthesis was high and vice versa. Sugars accumulated although enzyme activities were decreased under deficiency. The results show that growth of P- and S-starved plants is not limited by photosynthetic reactions.
1 The work was supported by the Deutsche Forschungsgemeinschaft. This article has been cited by other articles:
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