Procedures were developed to estimate the amount of glucose substrate required to biosynthesize shoot biomass of Pinustaeda L. By using compositional data from our own analyses and from the literature, glucose requirements per gram of major biomass constituent fractions were calculated to be as follows: lipids, 3.019 g; phenolics, 1.919 g; lignin, 1.897 g; nitrogenous compounds, 1.579 g; organic acids, 1.484 g; and carbohydrates, 1.182 g. From determinations of shoot weight and composition we calculated that 1.574 g of glucose was required to produce 1 g of typical shoot biomass.The computational procedures were also applied to analytical data from four other tree species, with glucose requirements estimated to range from 1.216 g for the cambial zone of Eucalyptusregnans F. Muell. to 1.603 g for bark of Pinuselliottii Englm.Application of our findings to studies of biomass formation of forest trees are discussed.
Seasonal patterns of change in lipids, sugars, starch, labile (ethanol soluble) constituents, holocellulose, and lignin were studied in six forest-grown white oak (Quercusalba L.) trees. Contents of metabolically active constituents in leaves, twigs, branches, boles (upper and lower), and roots (support and small lateral) were used to construct whole-tree budgets of energy allocation. [14C]Sucrose was also concurrently supplied to the study trees to follow the fate and efficiency of utilization of food reserves. Results showed that white oak rapidly mobilized and replaced food reserves during the critical period of canopy generation in the spring. Starch was more important as a reserve food than lipids or sugar. Large fluctuations in starch in roots in spring and fall suggested a bimodal belowground growth pattern. Labile constituents showed the most pronounced seasonal changes and dominated the calculated whole-tree energy flux patterns. Rapid decline in labile compounds in early spring and a parallel increase in holocellulose suggested a possible pattern of mobilization and resupply of stored reserves associated with in cell wells. This possibility was supported by a concurrent shift of labile 14C to nonlabile 14C in tissues. Canopy generation was calculated to have cost ≤17.7 kg of glucose (1.6 g glucose/g of canopy) of which 13 kg appeared to have come from within the canopy.
Small seedlings of five pine species (Pinus strobus, echinata, elliottii, serotina, and taeda) were exposed to low levels of ozone for periods from 5 to 22 weeks. Exposure to 5 parts per hundred million ozone resulted in significant increases in total soluble carbohydrates, reducing sugars, and ascorbic acid. In seedlings exposed to 15 pphm ozone, soluble sugars were higher than in the controls but ascorbic acid levels were not.
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