Acclimation of poplar trees to heavy metals in polluted habitats: I. Carbohydrate metabolism in fine roots of Populus deltoides

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 Populus deltoides 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

Photochemical activity, photosynthetic pigments and carbohydrates in poplar leaves fumigated with sulphur dioxide

The purpose of this study was to assess the influence of SO2 on photosynthetic apparatus and the level of total nonstructural carbohydrates (TNC) in developing and mature leaves of poplar (Populus deltoides). Photosynthetic apparatus was evaluated on the basis of fluorescence parameters (Fv/Fm, OPSII, qP and Rfd) and photosynthetic pigments (chlorophylls and carotenoids). Cuttings of poplar were exposed to 0.25 ppm of SO2 at 25°C and 200-300 mmol m-2s-1 PAR for 6 hours daily during 5 days in a fumigation chamber. The fumigation did not produce any significant differences in fluorescence parameters in neither developing nor mature leaves. In some mature leaves the concentration of pigments increased under the influence of SO2. Soluble carbohydrates decreased significantly both in developing and mature leaves and this was accompanied with an increase in starch accumulation. We suggest that Populus deltoides is a species tolerant to sulphur dioxide and the used SO2 dosage did not significantly impair the light reactions of photosynthesis, but it disturbed the accumulation of starch and the utilization of soluble carbohydrates in plants exposed to SO2

Acclimation of respiratory temperature responses in northern and southern populations of Pinus banksiana

Temperature acclimation of respiration may contribute to climatic adaptation and thus differ among populations from contrasting climates. Short-term temperature responses of foliar dark respiration were measured in 33-yr-old trees of jack pine (Pinus banksiana) in eight populations of wide-ranging origin (44–55°N) grown in a common garden at 46.7°N. It was tested whether seasonal adjustments in respiration and population differences in this regard resulted from changes in base respiration rate at 5°C (R5) or Q10 (temperature sensitivity) and covaried with nitrogen and soluble sugars. In all populations, acclimation was manifest primarily through shifts in R5 rather than altered Q10. R5 was higher in cooler periods in late autumn and winter and lower in spring and summer, inversely tracking variation in ambient air temperature. Overall, R5 covaried with sugars and not with nitrogen. Although acclimation was comparable among all populations, the observed seasonal ranges in R5 and Q10 were greater in populations originating from warmer than from colder sites. Population differences in respiratory traits appeared associated with autumnal cold hardening. Common patterns of respiratory temperature acclimation among biogeographically diverse populations provide a basis for predicting respiratory carbon fluxes in a wide-ranging species