Effect of Osmotic Water Stress on Germination and Initial Development of Ponderosa Pine Seedlings

Abstract

Seeds were subjected to three pregermination treatments—soaked in water 24 hours, alternately wetted and dried five times, and air-dried (control treatment)—then germinated on paper toweling saturated with graded polyethylene glycol (PEG-400) solutions made up to provide osmotic potentials of 0, -3, -7, -11, and -15 bars. Seedlings were watered with one of the five PEG-400 solutions with nutrients added. Air-dried seeds germinated as well as alternately wetted and dried, and significantly better than 24-hour soaked seed at 0, -3, and -7 bars. Osmotic potentials below -7 bars greatly depressed germination within all pretreatments. In general, root penetration, root dry weight, and cotyledon length decreased with decreased osmotic potential of the soil solution. Seedlings that germinated at low osmotic potentials grew poorly even when watered with solutions of high osmotic potential.