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The decay of coarse woody debris is a key component in the formation of forest soil and in the biogeochemical cycles of Ca and Mg. We tracked changes in density and concentration of Ca and Mg in sapwood of red maple (Acer rubrum L.), red spruce (Picea rubens Sarg.), paper birch (Betula papyrifera Marsh.), and eastern hemlock (Tsuga canadensis (L.) Carr.) in Maine and New Hampshire. We repeatedly sampled 10 logs of each combination of tree species and location at the time of felling and at 2-year intervals for 6 years (birch and hemlock) or 8 years (spruce and maple). We found that density loss was essentially linear for the time period investigated, with birch and maple sapwood decaying at faster rates than spruce and hemlock. Repeated-measures analysis and regression modeling of log-transformed concentrations indicated a significant accumulation of Ca for sapwood of all tree species at both locations (30%–90% increase after 6–8 years of ground contact). Regression estimates of Mg concentration in spruce and maple declined about 20% during the 8 years of ground contact. There was no significant trend for Mg concentration in birch and hemlock. Variation in decay rates and trends in Ca and Mg concentration may be due to differences in sapwood quality, the community of wood decay fungi and associated organisms, or to abiotic conditions. [ABSTRACT FROM AUTHOR]

Increased aluminum (Al) solubility in soil waters due to acid precipitation has aroused considerable interest in the problem of Al toxicity in plants. In the present study, an in vitro suspension culture system of Catharanthus roseus (L.) G. Don was used to analyze the effects of aluminum on several biochemical processes in these cells. The aliphatic polyamines, spermine and spermidine, and their precursor, putrescine, have been implicated in a number of stress responses of plants. Addition of 0.2, 0.5 or 1.0 mM AICl3 to cells cultured for 3 days caused a small but significant increase in cellular levels of putrescine at 4 h followed by a sharp decline by 16 h. There was no further decline in levels of putrescine during the next 32 h. Spermidine levels did not change appreciably compared to those in the control cultures. However, spermine levels increased by 2-3 fold at 24 and 48 h. Cellular activities of arginine decarboxylase (ADC; EC 4.1.1.19) and S-adenosylmethionine decarboxylase (SAMDC: EC 4. 1.1.50) were both inhibited by 20-25% at 4 and 7 h. Ornithine decarboxylase (ODC: EC 4.1.1.17) was less than 10% of ADC activity at all times. Whereas all concentrations of Al caused a slight decrease in total cell number, cell viability was affected only by 1.0 mM Al. There was a decrease in the cellular levels of Ca, Mg, Na, K, Mn, P and Fe in the cells treated with Al at 4 h, but a significant increase by 16 and 24 h. The results presented here suggest that both the absolute amounts of Al and the length of exposure to it are important for cell toxicity. [ABSTRACT FROM AUTHOR]

Highlights: [•] We use EDXRF to identify trends in high-resolution cation distribution in tree rings. [•] Potassium counts are elevated in sapwood and infected wood. [•] Localized peaks in calcium counts can be associated with crystals in wood. [•] Intra-annual variation in peak counts appears associated with ring boundaries. [ABSTRACT FROM AUTHOR]