Abstract
Concentrations of total nonstructural carbohydrates (TNC), soluble carbohydrates, starch, sucrose, glucose, fructose, raffinose, galactose, stachyose, mannitol and specific activities of soluble acid (AI) and neutral (NI) invertases, sucrose synthase (SuSy), hexokinase (HK), fructokinase (FK), glyceraldehyde 3-phosphate dehydrogenase (GAPDH) and glucose 6-phosphate dehydrogenase (G6PDH) were analyzed in fine roots of <em>Populus deltoides</em> Bartr. ex Marsh growing at a polluted site (near copper smelters) and a control site (free from heavy pollution). Also chemical properties of the soil from both sites were assessed. In comparison with the control, fine roots from the polluted site contained greater concentrations of TNC, soluble sugars, starch and sucrose but less hexoses, so they had higher values of sucrolysis index (sucrose/hexoses). The activity of AI, NI and SuSy declined insignificantly, while specific activities of HK, FK, GAPDH and G6PDH were significantly inhibited. The results suggest that a long-term heavy metal stress leads to an accumulation of carbohydrates and altering activities of glycolysis and the oxidative pentose phosphate pathway in fine roots.
Highlights
Many publications document the harmful effects of heavy metals on plant growth, and roots are the plant organs that suffer frequently from it (Breckle 1991)
Little is known about the effects of heavy metals on carbohydrate metabolism in the roots
To obtain more conclusive information on alterations induced by heavy metals in carbohydrate metabolism, we intended to study changes in the activity of enzymes involved in sucrolysis and glycolysis and the levels of particu
Summary
Many publications document the harmful effects of heavy metals on plant growth, and roots are the plant organs that suffer frequently from it (Breckle 1991). The most important role in plants is played by sucrose. It is the major energy-storage compound, the main sugar transported in sieve tubes, a substrate for biosynthesis of amino acids, fatty acids and many other. Sucrose is degraded and the resultant hexoses and their derivatives are used as sources of energy and carbon skeletons, which are necessary for growth, development and accumulation of storage compounds (Sturm and Tang 1999). To obtain more conclusive information on alterations induced by heavy metals in carbohydrate metabolism, we intended to study changes in the activity of enzymes involved in sucrolysis and glycolysis and the levels of particu-
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