Pollen maturation

Mlcroaporogeneala la a prominent feature of anther development. After the dlalntegration of tatrada hy degradation of the aurrounding callose the production of aeveral aecondary producta occurs during the following pollen maturation. 

Finally, a characteristic reaction of the flavonold stage is the glycosylatlon of the flavonols. The studies on the substrate specifity of this reaction have not yet been fully completed. The results until now indicate highest enzyme activity of a UDPG-O-glu-cosyltransferase at the completion of pollen maturity, which is the stage with an intensive formation of flavonol glycosides. 

Touraev, A., Heberle-Bors, E., 1999. Microspore embryogenesis and in vitro pollen maturation in tobacco. In Hall, R.D. (Ed.), Methods in Molecular Biology, vol. Ill Plant Cell Culture Protocols. Humana Press, Totowa, pp. 281-291. 

It is interesting that dramatic differences are often observed between 4x (female) X 2x and 2x (female) X 4x erosses. This is presumably beeause the diploid parent in a 4x X 2x eross produees 2n pollen via a first division restitution meehanism, while that in a 2x X 4x eross produees 2n eggs via a second division restitution meehanism. As diseussed above, the genetic consequences of first division restitution meehanism are very different than those of seeond division restitution. Offspring Ifom 4x X 2x erosses produee higher delds and tuber dry matter eontent than those from 2x X 4x erosses (Kidane-Mariam and Peloquin, 1974 Hutten et al., 1994). However, there is no differenee between the eross types for vine maturity and ehip eolor. 

The viability of seeds produced by S. divinorum is questionable. It is apparently a self-sterile plant which will produce seed only when cross-pollinated (1). Valdes pollinated fourteen flowers and four produced seeds. Unfortunately, the seeds viability could not be assessed as they were accidentally killed when a growth chamber overheated (1). Generally, this plant is reproduced by cuttings. It is a diploid species (N=l 1) whose pollen grains are not as viable as those of other Salvia species. Out of 3027 pollen grains, Reisfield found that 53% aborted, although this fact alone does not explain why the plants do not set seed in Mexico (16). Even when 5. divinorum is hand pollinated, only 2 to 3 percent of the nutlets fully mature (8). 

Staplin, F. Determination of thermal alteration index from color of exinite (pollen, spores), in How to assess maturation and paleotemperatures, (eds. Staplin, F. L., et al.) SEPM Short Course 7, p. 91, Tulsa OK, SEPM 1982... 

The first ALS-resistant weeds were reported in 1987 when prickly lettuce (Mallory-Smith, 1990 Mallory-Smith et al, 1990b) and kochia (Primiani et al, 1990) control failures occurred in Idaho and Kansas, respectively, after 5 consecutive years of chlorsulfuron use. The kochia biotype proved to be cross-resistant to six other ALS-inhibitor herbicides, including sulfonylureas and imidazolinones. Within 5 years, sulfonylurea-resistant kochia had been identified at 832 sites in 11 states of the United States and in three Canadian provinces (Saari et al, 1994). ALS inhibitor-resistant kochia and Russian thistle have become widespread problems in cereal-producing regions of northwestern United States and Canada. The mobility of these tumble weeds as plants with mature seeds or pollen carried by wind has undoubtedly contributed to the rate at which resistance has spread. 

It was concluded that late-maturing clones should be given an 11-hour short-day treatment for 4 weeks. This induced nearly all the clones tested to flower in time to produce adequate pollen for crossing purposes (Mesken, 1988). To make crosses, pollen from the male parent is collected in a paper bag and pollination is carried out by hand using a small brush (Mesken, 1988). 

From the assemblages of fossil pollen, palynologists make inferences about the types of forests or other plant communities that may have occurred in the local environment. These interpretations must be made carefully, however, because species are not represented in the pollen record in ways that directly reflect their abundance as mature plants. For example, pollen of wind-pollinated species is relatively abundant in lake sediments, whereas species that are insect pollinated are not well... 

---