An influence of abiotic factors on the germinability of Agrostis species and Poa species

The objective of this contribution is to interpret the impact of some abiotic factors on the germinability. Primarily was observed the stress that they cause on germinability and also on the energy of other perennial grass caryopsis' germinability. Withal there were considered differences in germinability of some perennial grass species, variances of strains and the influence of today`s seeds dressing technologies, which are used to improve the germination. The light factor has the biggest influence of all factors on germination of Agrostis stolonifera (Penn G-2, Providence), Poa supina (Supranova) and Poa pratensis (Julius, Julius PreGerm). All these species had germination evidential higher in the light, than in the dark. With species Poa pratensis (Coctail, Coctail Headstart) and Poa annua were not observed any essential variations between the dark and the light variants. Only with Poa annua there were reached noticeably lower values with variant in the light, where was used polyethyleneglycol, than in the dark. The analysis of variance demonstrated, that the biggest influence had the factor of stratification together with the light factor with Agrostis capilaris (Bardot) and Agrostis stolonifera Providence. With Poa annua there was established the biggest influence of the light factor together with the factor of the used medium. The factor of stratification noticeably affected only the germination of Agrostis capillaris Bardot. The germination of Agrostis stolonifera Providence, Poa pratensis Cocktail, Cocktail Headstart, Julius and Poa annua was not noticeably affected by stratification. The reaction on the factor of stratification was with Agrostis capillaris Bardot in the dark adverse and in the light minimal. Poa pratensis Julius PreGerm germination was negative in the dark as well as in the light. With Poa supina Supranova it was not the most important factor, but still affected the germination significiantly. The nitrogen nutrition, as the next factor, had positive affect with all variants. This could be explained with existence of the „gap detection“ mechanism. Especially variants in the dark and with used stratification had affected theirs germination positively, when combinated with H2O and potassium nitrate. The addition of potassium nitrate positively affected also the energy of germination.With the lack of water factor was affected amount of germinated caryopsis and their energy of germination. Especially with higher water tonus was energy of germination and germination itself decreased. The only exceptions were these variants in the dark with the stratification factor. With these conditions was achieved the same or even higher quality of germination of variants, where PEG was added than was achieved with H2O variants.

Tolerance of Supina Bluegrass to Pre and Post-Emergence Herbicides

Supina bluegrass (Poa supina) is being increasingly used for shaded lawns and golf course tees due to its excellent shade tolerance. The herbicide tolerance, however, is undocumented because herbicide use on amenity turfs is banned in the European countries where supina bluegrass has been used for over 30 years. Several commonly used turf and ornamental herbicides are capable of harming or eradicating close relatives of supina bluegrass. In particular, Prograss (Ethofumesate) is used to selectively remove annual bluegrass (Poa annua) from mixed turf stands. Supina bluegrass is a putative ancestor of annual bluegrass and may have similar susceptibilities to chemicals. Fifteen pre and postemergence turf and ornamental herbicides were tested for their potential to damage or kill a mature stand of supina bluegrass. Field trials were conducted twice over two growing seasons. Herbicides with the active ingredients triclopyr, MCPP, quinclorac, and ethofumesate caused temporary phytotoxicity in at least one of the two years. Fall applications of Prograss (Ethofumesate) and Turflon Ester (Triclopyr) caused phytotoxicity the spring following autumn application in both years, while Strike 3 (Dicamba, MCPP, 2,4-D) and Confront (Triclopyr + Clopyralid) caused phytotoxicity in one year only. None of the compounds showed potential for selectively removing supina bluegrass from a mixed turf stand.

EVOLUTIONARY ORIGIN OF POA ANNUA L. IN THE LIGHT OF KARYOTYPIC STUDIES

From a karyotype analysis of Poa annua (2n = 28) two large chromosomes, I and II, and one small chromosome, XIV, as well as three chromosome groups containing two, four and five chromosomes have been identified. From a comparison of the karyotype of Poa annua with that published of Poa exilis (2n = 14) and Poa supina (2n = 14), doubt is cast on the theory that Poa annua is an allotetraploid of the two latter diploid species. The three chromosomes of Poa annua that could be identified with certainty existed in homologous pairs, indicating that the species could have originated from Poa exilis or Poa supina and one other hitherto unidentified species. It is suggested that further work on the karyotype of diploid species might reveal further useful information on the evolutionary history of the species.