The ecological and evolutionary aspects of planned introductions of transgenic organisms into the environment are considered in this report. The authors support the timely development of environmentally sound products, such as improved agricultural varieties, fertilizers, pest control agents, and microorganisms for waste treatment, through the use of advanced biotechnology within the context of a scientifically based regulatory policy that encourages innovation without compromising sound environmental management. Economic, social, and ethical concerns also must be weighed along with strictly ecological and evolutionary considerations, but these other issues are beyond the scope of this report. Ecological oversight of planned introductions should be directed at promoting effectiveness while guarding against potential problems. The diversity of organisms that will be modified, functions that will be engineered, and environments that will receive altered organisms makes ecological risk evaluation complex. While we cannot now recommend the complete exemption of specific organisms or traits from regulatory oversight, we support and will continue to assist in the development of methods for scaling the level of oversight needed for individual cases according to objective, scientific criteria, with a goal of minimizing unnecessary regulatory burdens. In this report, we provide a preliminary set of specific criteria for the scaling of regulatory oversight. Genetically engineered organisms should be evaluated and regulated according to their biological properties (phenotypes), rather than according to the genetic techniques used to produce them. Nonetheless, because many novel combinations of properties can be achieved only by molecular and cellular techniques, products of these techniques may often be subjected to greater scrutiny than the products of traditional techniques. Although the capability to produce precise genetic alterations increases confidence that unintended changes in the genome have not occurred, precise genetic characterization does not ensure that all ecologically important aspects of the phenotype can be predicted for the environments into which an organism will be introduced. Many important scientific issues must be considered in evaluating the potential ecological consequences of the planned introduction of genetically engineered organisms into the environment. These include survival and reproduction of the introduced organism, interactions with other organisms in the environment, and effects of the introduced organism on ecosystem function. We encourage the use of small—scale field tests , when justified by previous laboratory and/or greenhouse studies, under conditions that minimize dispersal and under appropriate regulatory oversight. As the biotechnology industry develops, continuing regulatory oversight as well as long—term research and monitoring will be necessary for responsible risk management. Many engineered organisms will probably be less fit than the parent organism, although some importan...

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The hypothesis that carbohydrate partitioning is driven by competition among individual plant organs, based on each organ's growth potential, was used to develop a simulation model of the carbon supply and demand for reproductive and vegetative growth in peach trees. In the model, photosynthetic carbon assimilation is simulated using daily minimum and maximum temperature and solar radiation as inputs. Carbohydrate is first partitioned to maintenance respiration, then to leaves, fruits, stems and branches, then to the trunk. Root activity is supported by residual carbohydrate after aboveground growth. Verification of the model was carried out with field data from trees that were thinned at different times. In general, the model predictions corresponded to field data for fruit and vegetative growth. The model predicted that resource availability limited fruit and stem growth during two periods of fruit growth, periods that had been identified in earlier experimental studies as resource-limited growth periods. The model also predicted that there were two periods of high carbohydrate availability for root activity. The fit between model predictions and field data supports the initial hypothesis that plants function as collections of semiautonomous, interacting organs that compete for resources based on their growth potentials.

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