Germination of cariopsids classified by size and diaspores of four pastures for semi-arid rain-fed

Abstract

In Poaceae, the commercial seed or propagule consists of  the spikelet or diaspora: caryopsis (Cs) + accessory bracts:  usually glumes, lemurs, paleas and sometimes species  specific, modified branches, which have an effect on  germination, and influence the management required and  therefore the biological quality of the seed. The removal  of accessory bracts with or without Cs classification by  size is an undocumented alternative in the establishment  of rain-fed praires. The objective of this paper was  to evaluate germination by sowing every 30 days, Cs  classified from pasture, two native and two introduced,  obtained from commercial diaspores at the beginning  of the experiment (Cs base -CsB) or every 60 days (Cs  control-CsT), for 15 months; similarly, to evaluate the  emergence of seedlings from diaspores. The propagules  (diasporas or Cs) were evaluated from February 2010 to  May 2011, in laboratory. Native and introduced species  included Bouteloua gracilis, B. curtipendula, Cenchrus  ciliaris and Chloris gayana, respectively. From diaspores,  accessory bracts were removed and the resulting Cs were separated with sieves into large (CsG), medium (CsM)  and small (CsCh). They were sown based on viable  pure seed, the different sizes of Cs, on wet paper, as  diaspores at 1 cm depth, in peat moss. The behavior of the  germination was analyzed by logistic regression with the  Logistic routine of SAS. In the evaluated species, larger  Cs size was associated with higher germination and the  covariables benefit and storage time were significant (p<  0.001). Germination in native pastures tended to decrease  with time, contrary to introduced ones and germination  was higher in direct relation to the Cs size. The viability  is best preserved by maintaining the Cs with accessory  bracts; but in introduced species germination increased  when they were eliminated.