Summary and general conclusions

In general, increased temperatures and well-watered soil promote plant growth and thus flowering and seed production (a component of fitness), but drought stress can override the benefits of increased temperatures on seed production and may cause a decrease in seed quality. However, a short rainless period is an environmental cue for onset of flowering of some trees in tropical wet forests, especially if it is accompanied by a slight decrease in temperature. Heatwaves at the time of pollination can have detrimental effects on pollen viability, thereby causing low seed set, for example, in Zea mays. Notably, in hot and cold deserts and in a Mediterranean climate the timing of adequate soil moisture for seed germination (autumn-winter vs spring), especially for annuals, has significant effects not only on seedling survival but also on plant growth and seed production. Increased atmospheric nitrogen (N) deposition has the potential to increase the growth and seed production of plants if soil moisture is not limiting. In general, CO2 enrichment increases seed production, but the response is highly species-specific.