Light affects the germination and normal seedling development of Neotropical savanna grasses

Abstract

The Cerrado is a Neotropical savanna where grasses are a major biomass component in the open vegetation physiognomies. Invasive grasses are widely used as pastures in the Cerrado, and their presence may displace native species. The persistence of native grasses relies also on reproduction via seeds, which is often dependent on seeds found buried in the soil seed bank. The literature about the effects of light availability on the germination of Neotropical savanna grasses is scarce, and germination may lead to abnormal seedlings that develop only the root or the shoot. Germination trials that overlook this fact may overestimate the potential for seedling recruitment. Therefore, we tested the effects of light availability on the germination of nine native and two invasive grasses, addressing the production of normal seedlings. Seeds were germinated in the complete absence or the presence of light (12 h photoperiod under white light) for 30 days. Germination was defined as the sum of normal and abnormal seedlings. Eight species were light-dependent, decreasing the production of normal seedlings in the dark. Two native and one invasive species were non-responsive to the dark treatment, showing no change in germination or production of normal seedlings. Our results suggest that seeds buried in the soil seed bank are likely to show reduced germination and develop abnormal seedlings, reinforcing a bottleneck for the recruitment of native grasses. For invasive species, however, the potential of seedling recruitment was minimally reduced by light, suggesting a competitive advantage for the recruitment of these species.

Efficacy of S-metolachlor + glyphosate for Weed Control in Different Levels of Eucalyptus Straw

“…This occurred because the greater volume of straw reduces average daily soil temperature [37] and exposure to light, which are the main regulators of seed germination [38][39][40][41]. The unavailability of light also causes the emergence of abnormal grass seedlings, with the development of only the aerial or root part, which limits photosynthesis and nutrient absorption, leading to the death of the seedlings [42]. Grass seeds germinate at a maximum depth of 5.2 and 9 cm [43,44], so the thicker the straw layer, the lower the germination, reducing fresh and dry mass and controlling weeds [45].…”