PubMed · 12285660
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1992. Environmental problems and developing countries.. https://pubmed.ncbi.nlm.nih.gov/12285660/
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Stimulation of vegetative growth by an elevated CO(2) concentration does not always lead to an increase in reproductive yield. This is because reproductive yield is determined by the fraction of biomass allocated to the reproductive part as well as biomass production. We grew Xanthium canadense at low N (LN) and high N levels (HN) under an ambient (360 micromol mol(-1)) and elevated (700 micromol mol(-1)) CO(2) concentration ([CO(2)]) in open-top chambers. Reproductive yield was analysed as the product of: (1) the duration of the reproductive period, (2) the rate of dry mass acquisition in the reproductive period, and (3) the fraction of acquired biomass allocated to the reproductive part. Elevated [CO(2)] increased the total amount of biomass that was allocated to reproductive structures, but this increase was caused by increased capsule mass without a significant increase in seed production. The increase in total reproductive mass was due mainly to an increase in the rate of dry mass acquisition in the reproductive period with a delay in leaf senescence. This positive effect was partly offset by a reduction in biomass allocation to the reproductive part at elevated [CO(2)] and HN. The duration of the reproductive period was not affected by elevated [CO(2)] but increased by HN. Seed production was strongly constrained by the availability of N for seed growth. The seed [N] was very high in X. canadense and did not decrease significantly at elevated [CO(2)]. HN increased seed [N] without a significant increase in seed biomass production. Limited seed growth caused a reduction in biomass allocation to the reproductive part even though dry mass production was increased due to increased [CO(2)] and N availability.
Modified atmosphere packaging (MAP) is commercially used to increase the shelf life of packaged produce by reducing the produce respiration rate, delaying senescence, and inhibiting the growth of many spoilage organisms, ultimately increasing product shelf life. MAP systems typically optimize O(2) levels to achieve these effects while preventing anaerobic fermentation but fail to optimize CO(2) concentrations. Altering film permselectivity (i.e., beta, which is the ratio of CO(2)/O(2) permeation coefficients) could be utilized to concurrently optimize levels of both CO(2) and O(2) in MAP systems. We investigated the effect of modifying film permselectivity on the equilibrium gas composition of a model MAP produce system packaged in containers incorporating modified poly(ethylene) ionomer films with CO(2)/O(2) permselectivites between 4-5 and 0.8-1.3. To compare empirical to calculated data of the effect of permselectivity on the equilibrium gas composition of the MAP produce system, a mathematical model commonly used to optimize MAP of respiring produce was applied. The calculated gas composition agreed with observed values, using empirical respiration data from fresh cut apples as a test system and permeability data from tested and theoretical films. The results suggest that packaging films with CO(2)/O(2) permselectivities lower than those commercially available (<3) would further optimize O(2) and CO(2) concentration in MAP of respiring produce, particularly highly respiring and minimally processed produce.
An open-top chamber experiment with field grown potato (Solanum tuberosum L. cv. Bintje) was performed in the south-west of Sweden in 1998. The experiment was aimed to investigate individual and interactive impacts of elevated ozone (O(3)) and carbon dioxide (CO(2)) on potato growth and yield. Treatments were ambient and elevated CO(2) with or without the addition of 20 nmol mol(-1) O(3). In addition, plants were grown in ambient air plots. Plants grown in elevated CO(2) and O(3) had a reduced tuber yield, compared to control, by 2% and 8%, respectively. These effects were, however, not statistically significant. Elevated CO(2) caused a significantly larger number of tubers of lower average size, while elevated O(3) induced significantly lower tuber dry matter content. The number of tuber initials (tubers <15 mm) found at harvest was significantly lower in elevated O(3). Visible O(3) leaf injury appeared earlier and the number of yellow leaves 89 days after emergence was significantly larger in elevated O(3). In elevated CO(2), haulm dry weight was significantly (15%) lower at harvest and the haulm/tuber ratio was significantly reduced. There were significant interactive effects of O(3) and CO(2) on the final number of leaves and on stem height. Plants in elevated CO(2) reached final stem height earlier than in the other treatments. In summary, it was concluded: (a) that anticipated future O(3) levels are likely to have a negative impact on potato growth, although tuber yield effects may be hard to demonstrate experimentally in this plant due to large variation; (b) that whether any possible beneficial effect of elevated CO(2) on the magnitude of tuber yield will be expressed, depend on the climatic conditions prevailing; and (c) that potato growth responses to CO(2) and O(3) are not simply additive.