Differential incidence of the lemma on seed germination among different Paspalum dilatatum genotypes

Abstract

-Paspalum dilatatum Poir. is a promising perennial summer grass forage for temperate regions, but among other factors, slow stand establishment has hindered its adoption. One of the reasons may be seed dormancy. Intraspecific variability in seed dormancy has been reported in P. dilatatum, but the mechanisms underlying this variability remain unclear. In this paper, we focus on the role of seed external covering structures on germination, particularly the lemma. Seeds of apomictic and sexual biotypes of P. dilatatum were subjected to acid scarification and removal of the lemma to study their germination, imbibition rate and sensitivity to ABA. Seeds without lemma showed higher germination than other treatments in dormant genotypes. We found that the lemma delayed but did not prevent water uptake in any genotype. Comparing sexual biotypes, P. dilatatum subsp. flavescens showed higher lemma-imposed dormancy than P. dilatatum "Virasoro", and also higher seed dormancy at the caryopsis level. The thickness of the lemma was not different between these biotypes, so this trait did not explain differences in dormancy. Intraspecific variability of seed dormancy in this species may be attributable to the lemma incidence, however differences in the caryopsis component of seed dormancy should be considered.Index terms: perennial warm-season forage grasses, seed dormancy, seed covering structures, acid scarification.Impacto diferencial da lema sobre a germinação de sementes entre diferentes genótipos de Paspalum dilatatum RESUMO -Paspalum dilatatum Poir. é uma gramínea forrageira perene de regiões temperadas, mas sua utilização é limitada pelo seu estabelecimento lento, entre outros fatores. Uma razão pode ser a dormência das sementes. Tem sido relatada variabilidade intraespecífica da dormência em P. dilatatum, mas os mecanismos envolvidos nesta variabilidade não são claros. Neste trabalho estudamos o papel das coberturas externas sobre a germinação, particularmente da lema. Sementes de biótipos sexuais e apomíticos de P. dilatatum foram submetidos à escarificação ácida e remoção da lema para estudar a germinação, a taxa de embebição e a sensibilidade ao ABA. As sementes sem lema mostraram maior germinação que outros tratamentos em genótipos com dormência. Ainda, a lema retarda, mas não impede a entrada de água. Comparando genótipos sexuais, P. dilatatum subsp. flavescens apresentou uma maior dormência imposta pela lema que P. dilatatum "Virasoro", e também dormência mais elevada ao nível do cariopse. A espessura da lema não foi diferente entre estes genótipos, e portanto esta não explicou as diferenças na dormência. A variabilidade intraespecífica da dormência nesta gramínea panicóide pode ser atribuída às diferenças na incidência da lema. Contudo, diferenças na dormência ao nível da cariopse devem ser consideradas.Termos de indexação: gramínea forrageira perene estival, dormência das sementes, coberturas externas das sementes, escarificação ácida.

Modelling seedling emergence in Paspalum species using environmental data from field experiments

“…Paspalum dilatatum Chirú showed the lowest emergence timing and the highest maximum emergence proportions among Paspalum genotypes for both irrigation treatments. This seedling emergence behaviour is congruent with our previous results showing that the seed dormancy of the Chirú biotype is lower than that of other genotypes of P. dilatatum (Glison et al., 2015, 2017).…”

“…In seeds with similar anatomy the leafy glumes have no effect on dormancy or germination (Duclos et al., 2013); however, the hard lemma and palea of the fertile floret may be strongly implicated. Although water intake is restricted by these structures, they allow sufficient imbibition of the caryopsis to trigger germination (Duclos et al., 2013; Gallart et al., 2008; Glison et al., 2017; West & Marousky, 1989). Scarification procedures or a dry storage period can also be applied to obtain seed lots with lower seed dormancy level (Glison et al., 2015, 2017; Maeda et al., 1997; West & Marousky, 1989).…”

“…Although water intake is restricted by these structures, they allow sufficient imbibition of the caryopsis to trigger germination (Duclos et al., 2013; Gallart et al., 2008; Glison et al., 2017; West & Marousky, 1989). Scarification procedures or a dry storage period can also be applied to obtain seed lots with lower seed dormancy level (Glison et al., 2015, 2017; Maeda et al., 1997; West & Marousky, 1989). Environmental conditions like alternating temperatures, chilling, nitrate or light may also break dormancy and increase germination (Glison et al., 2015; Johnston & Miller, 1964; Schrauf et al., 1995).…”

“…Environmental conditions like alternating temperatures, chilling, nitrate or light may also break dormancy and increase germination (Glison et al., 2015; Johnston & Miller, 1964; Schrauf et al., 1995). Taking several factors into account, in previous work with these species we have shown that, in general, all seeds with a fully developed viable caryopsis can germinate if adequate conditions are met (Glison et al., 2015, 2017).…”

Thermal Stress in the Adequacy of the Chemical Scarification Period in Brachiaria Seeds

“…These findings indicate the existence of distinct mechanisms associated with dormancy in the seeds of forage species. Glison et al (2017) found a difference concerning dormancy between Paspalum dilatatum genotypes due to the motto's incidence. Luccas et al (2018) demonstrated that in Urochloa humidicola, dormancy involves the remaining structure of the caryopsis and the increase in the growth potential of the embryo during storage in addition to the gibberellin and abscisic acid (promoter/inhibitor) balance.…”