Centotheca lappacea from subfamily Panicoideae (family Poaceae) (Sánchez-Ken and Clark, 2010) is a perennial grasses with 30-100 cm long erect culms. It is used as a forage grass and widely native from west Tropic Africa, Temperate Asia, Tropic Asia, Australia, and Pacific Island (USDA, 2014), and mainly grows invasive in clearings, forest edges and paths, road sides, waste places, cocoa, oil palm and rubber plantations (Biotrop, 2014). In 2006, Ye shu reported the chromosome number 2n= 24, although Levy and Feldman (2002) suggested it might be more frequently polyploid. However the information about ploidy level and reproduction mode of this species still limited. Many widespread Panicoid grasses reproduce via apomixis (= asexual reproduction via seed) (Hojsgaard et al. 2013) which enhances colonization of new habitats and is a factor for invasiveness (Te Beest et al. 2012).
The aims of this research are to observe the reproduction mode of Centotheca lappacea and the chromosomal ploidy level. This information will be useful to investigate the key factors for introduced species to reach rapidly dominance in disturbed habitats. Our hypothesis is that Centotheca lappacea in the rainforest transformation systems of Sumatra is polyploid and mainly reproduces asexually via seed (apomixis).
All plant materials (leaves dried in silica gel, seeds, FAA fixations of flowering buds) were taken from 180 individuals from plots in oil palm plantation, rubber plantations, and jungle rubber of Bukit Duabelas and Harapan, in Jambi, Indonesia. The sampling scheme followed the plot design of the SFB Project 990 "Ecological and socioeconomic functions of tropical lowland rainforest transformation systems (Sumatra, Indonesia)". Ploidy levels will be screened by flow cytometry on leaf material, accompanied by chromosome counting from the roots tissue of seedlings will be conducted to define the ploidy level following methods by Hojsgaard et. al (2007). The mode of reproduction will be determined by the microscopic study of megasporogenesis and embryo sac development following methods by Hojsgaard et. al (2013). Flow Cytometric Seed Screen (FCSS) protocol described by Matzk et al. (2000) and Hojsgaard et al. (2013) will be followed to reconstruct the reproductive pathways of mature seeds.