Effects of polyethylene glycol on the morphology of ornamental seedlings

Osmotic compounds such as polyethylene glycol 8000 (PEG-8000) may control seedling elongation by imposing physiological drought. Tagetes patula (French marigold) and Impatiens wallerana (impatiens) were grown hydroponically in modified Hoagland solutions containing 0 to 62.5 g@L PEG-8000. Marigolds and impatiens were a maximum of 68% shorter when grown in -1 PEG-8000. In a separate experiment, PEG-8000 was incorporated into a growing medium from 0 to 83 g@L . Marigold and Salvia splendens (salvia) grown in 15-50 g@L of PEG-8000 emerged -1 -1 later than non-treated controls, and were up to 53% shorter, for salvia, or 38% shorter, for marigolds at harvest. PEG-8000 reduced leaf water and turgor potential, and marigolds grown in PEG-8000 photosynthesized less than non-treated seedlings. Finally, when PEG-8000 was applied to seedlings as a drench, 15-50 g@L of PEG-8000 reduced elongation. It appears that -1 PEG reduces elongation by reducing turgor potential and photosynthesis, not by delaying seedling development.