Seed longevity of Eragrostis plana Nees buried in natural grassland soil

Abstract

-The objective of this research was to evaluate the seed longevity of Eragrostis plana Nees buried at different soil depths, in a natural-grassland area in the Pampa biome (46 m altitude, 30º05´S and 51º40´W) of Rio Grande do Sul State, Brazil. The experimental design was a split-plot type in complete blocks with two factors: seeds buried at five different depth levels (soil surface and 2.5, 5, 10 and 20 cm) and seven exhumation dates. The blocks were allocated in natural grassland grazed by cattle, allocated in a 12-m-long transection. Fifty-four permeable nylon bags filled with 100 seeds in each division, with five vertical divisions, were buried in each row. Seven exhumation dates were used: the first on October 14, 2003 and the last on January 14, 2006. The percentage of viable seeds of E. plana, collected at seven exhumation times and set at different depths in the soil horizon, were described by simple negative exponential equations. Based on the model, the percentage of viable seeds collected at the five depths, (soil surface and 2.5, 5, 10, and 20 cm), after 2.5 years of burial, were 0.1, 0.5, 1.0, 7.4 and 22.1%, respectively. Increase in depth is directly associated with physical and physiological seed integrity of E. plana. Negative simple exponential equations can be used to predict seed longevity of E. plana buried in nylon bags. This invader species accumulates soil seed-bank of high longevity.

Biology of the invasive species Eragrostis plana in Southern Brazil: What have we learned and how may this help us manage it?

“…Although the ideal germination temperature is 35°C (Bittencourt et al, 2017; Maldaner et al, 2019), the species can germinate between 12.3 and 40°C (Bittencourt et al, 2017; Caratti, 2019). The secondary dormancy of E. plana seeds can be broken by cold (Medeiros et al, 2014). Light is a favourable condition, albeit not required for germination (Caratti, 2019).…”

“…Indeed, E. plana germination is difficult when buried more than 3 cm deep (Caratti, 2019), and when placed on the soil surface, the emergence rate was 87% (Bittencourt et al, 2017). Burial depth is directly associated with physical and physiological seed integrity, and viable seeds were collected up to 20 cm deep within 2.5 years of burial (Medeiros et al, 2014). Germination, which is closely related to water potential, could vary from 0 to 98% when potential varies from −1.2 to 0 MPa (Bittencourt et al, 2017).…”

Drought tolerance in tough lovegrass (Eragrostis plana): Understanding mechanisms and competitive ability

“…Rangeland pastures, such as those of southern Brazil, are characterised by a diversity of grass species with contrasting growth strategies (Marques et al, 2017); for example, the native C4 Paspalum notatum Flügge is used as a high quality forage species in areas of low precipitation in southern Brazil, due to its large and deep fibrous root system (Acuña et al, 2010). These drought avoidance characteristics, combined with high levels of root production (Abichequer et al, 2009), tolerance to low temperatures and high levels of seed production and viability (Medeiros et al, 2014), are shared between E. plana and P. notatum, likely leading to competition; however, a clear understanding of drought responses and associated interspecific competition between E. plana and P. notatum remains lacking. Thus, the aim of this study was to test for competitive differences in tolerance to drought conditions in the invasive species E. plana and the forage species P. notatum, due to variation in morphological, physiological, and biochemical trait responses to contrasting levels of water deficit.…”

“…This grass was accidentally introduced to Brazil in 1957 (Reis Leite, 1993) and has since been a threat to native forage species, due to its greater palatability and associated endozoochoric distribution of the potential 80 000 seeds that are produced per plant in one generation (Caratti, 2019). While the range of E. plana in Brazil extends to >10 000 km 2 , its distribution in the north contrasts with that across central regions (Medeiros et al, 2014).…”

Use of a wiper applicator for the control of the invasive species Eragrostis plana with glyphosate salts

“…South African lovegrass (Eragrostis plana Nees) is one of the main invasive species in the native grasslands of southern Brazil. It was accidentally introduced to the state of Rio Grande do Sul in the early 1950s (Medeiros et al, 2014). Propagules of the species were imported as contaminants in seeds of weeping lovegrass (Eragrostis curvula Schrad) and Rhodes grass (Chloris gayana Kunth), both of which were brought over from South Africa as new pasture species (Medeiros, Focht, 2007).…”