Seed Germination of American Pokeweed (Phytolacca Americana). I. Laboratory Techniques and Autotoxicity

Abstract

Seeds of pokeweed (Phytolacca americana L.), an underinvestigated species, were studied to determine optimal conditions for laboratory germination. Soaking seeds in acid solutions prior to sowing increased rates of germination. Concentrated (conc) H2SO4 was more effective than conc NO3 or conc HCl acids. Physiological evidence from seed germination studies suggests that autotoxicity, or intraspecific inhibition, exists in pokeweed, a species known to possess several biologically active compounds. Seed germination was investigated in the laboratory with aqueous extracts of vegetative and reproductive structures of the plant. The presence of extracts from most plant parts correlated with reduced or no germination by seeds of its own species, whereas the presence of distilled water correlated with high percentages of germination by control seeds. Whether diluted with water by 5‐fold (20% v/v) or undiluted, juice of pokeweed fruits completely inhibited the laboratory germination of pokeweed seeds. Also, extracts of freshly harvested mature leaves, stems, and immature fruits inhibited seed germination. However, results with root extracts, obtained from a single individual, depended more on concentration, since the highest concentration (50% v/v) inhibited germination, and lower concentrations (10 and 20% v/v) increased germination percentages over control samples. Results with extracts of juvenile leaves correlated with neither inhibition nor promotion of germination. Thus, except for juvenile leaves and the root, most extracts of the pokeweed plant inhibited seed germination with more mature structures exerting more inhibition and less mature structures exerting less or no inhibition. The ecological implication of autotoxicity is that seeds are more dispersed through time and space. In regard to seed germination by other species, especially those taxa known to possess biologically active compounds, these and other results suggest that the phenomenon of autotoxicity might be more widespread than previously suspected.

AUTOTOXICITY IN TOUGH LOVEGRASS ( Eragrostis plana )

“…Species that experience such autotoxic phenomenon are known to regulate their populations over space and time, avoiding intraspecific competition, guaranteeing self-perpetuation, allowing for a better geographical distribution (Singh et al, 1999). Moreover, such invasive characteristics provide selective advantage to autotoxic plants over other species (Picman and Picman, 1984;Edwards et al, 1988).…”

Allelochemical autotoxicity in the emergent wetland macrophyte Juncus effusus (Juncaceae)

“…Bell for their technical assistance. This paucity persists despite a suggestion that allelochemical autotoxicity may be a common phenomenon (Edwards et al, 1988). J.…”

“…Constructive critiques provided by Drs. Terrestrial examples of autotoxicity deal primarily with seed germination in food species (e.g., studies of fig, grape, peach, and sunflower mentioned by McNaughton, 1968) or weeds, such as pokeweed (Phytolacca americana; Edwards et al, 1988). B.…”

“…This paucity persists despite a suggestion that allelochemical autotoxicity may be a common phenomenon (Edwards et al, 1988). Terrestrial examples of autotoxicity deal primarily with seed germination in food species (e.g., studies of fig, grape, peach, and sunflower mentioned by McNaughton, 1968) or weeds, such as pokeweed (Phytolacca americana; Edwards et al, 1988). Reports of autotoxicity in aquatic systems have been cited for a number of algae (Inderjit and Dakshini, 1994), ferns (Osmunda spp.…”

Rock Phosphate as a Novel Solid-Phase Extraction Adsorbent for Analysis of Oxalic Acid in Plant Xylem Saps by Rp-HPLC

“…Moreover, it is a perennial herb that was recently found to be a hyperaccumulator with great potential for remediation of Mn and Cd contaminated soils. [13][14][15] Seeds of pokeweed were treated with concentrated sulfuric acid for 20 min to promote germination [16] and washed by deionized water. Then the seeds were placed in the dark on the wet filter paper at 25 C for germination.…”