Microspore and microgametophyte development in relation to biological activity of environmental pollutants.

The pattern of synthesis of nucleic acids and proteins in the development of the microspore and later during pollen germination and tube growth is discussed. In the pollen grain at the time of anthesis all the proteins that are required for germination and early tube growth are either already present, or if new proteins are synthesized, the messenger RNAs for their synthesis already exist in the ungerminated pollen grain. In addition, similar proteins are synthesized on new mRNAs during germination and pollen tube growth as are synthesized on premade mRNAs. The genetic program during at least the latter part of pollen maturation prior to anthesis is thus the same as that during pollen germination and tube growth. Accordingly, one cannot treat mature pollen with mutagens and expect to be able to score the pollen tubes for mutant proteins. Treatment with mutagenic compounds would have to be during pollen maturation in the anther, before the transcription for the proteins required during germination and pollen tube growth has occurred. Available evidence indicates that this is very early in pollen development, possibly soon after meiosis. The value of pollen tubes to monitor for chemicals that affect the intracellular motility systems of organisms is also discussed.