Pollen represents a critical stage in the life cycle of plants, as viable pollen is crucial for efficient sexual plant reproduction. However, pollen may also be a vector for transgene escape from genetically modified crops. To investigate the possible contribution pollen viability may play in determining transgene escape, the project described in this report had two objectives: to review the available literature on pollen viability and the effect of environmental factors on it, and to analyze the viability of pollen of various species in the environment.
Reviewing scientific literature on pollen viability it was found that pollen viability is mainly affected by drought/dehydration, heat stress and UV-B radiation. These factors not only affect pollen viability after dehiscence, when the pollen is exposed to the environment, but also during its development inside the anther. The effect of each factors affects pollen viability in a species-specific way, depending on the physiology of the pollen grains and the presence or absence of specific structural modifications. A complicating factor for the comparison of various experiments was the absence of standardized protocols and experimental conditions used. Assessing the contribution of pollen viability to transgene escape is further complicated by the fact that much of the literature described experiments that were performed in greenhouses with greenhouse-grown plants, and investigated the effect of a single factor only. Although informative, these experiments do not represent field situations and cannot be extrapolated to field situations without further experimental support. In conclusion, although considerable data is present is available on pollen viability, it is difficult to use it for the prediction of the contribution of pollen viability to transgene escape.