Germination and Root Growth of Two Noxious Weeds as Affected by Water and Salt Stresses

Abstract

Hoary cress germination decreased with lower osmotic potential. Knapweed germination was greatest at 0.0 and −0.5 MPa of osmotic potential. Salinity increases up to an electrical conductivity (EC) of 12 dS m-1 had no effect on germination of either species. Hoary cress and knapweed root growth were reduced by decreases in osmotic potential. Hoary cress root growth was not affected by increasing salinity up to an EC of 12 dS m-1. Knapweed root growth was reduced by the initial increase in salinity (4 dS m-1), but not by higher salt concentrations.

Plant life-form and germination in a Mexican inter-tropical desert: effects of soil water potential and temperature

“…The published evidence and our observations, however, oppose the germination behaviour of most plants in tropical and temperate habitats, and crops and annual plants in arid environments. For these the optimum water potential for germination coincides with the soil field water capacity and seed hydration, germination rate and germinability all decrease as water potential drops (Williams & Shaykewich, 1971;Mott, 1972;Romo & Haferkamp, 1987;Cluff & Roundy, 1988;Meidan, 1989;Evans & Etherington, 1990;Choinski & Tuohy, 1991;Khatri et al, 1991;Kiemnec & Larson, 1991;Qi & Redmann, 1993;Facelli & Ladd, 1996;Swaegel et al, 1997;Al-Karaki, 1998;Rowse et al, 1999).…”

The biology of Canadian weeds. 3. Lepidium draba L., L. chalepense L., L. appelianum Al-Shehbaz (updated)

“…A subsequent study showed rapid deterioration of L. chalepense seeds: 91% were not viable after 2 mo in water and all totally disintegrated after 19 mo, while seeds in dry storage declined gradually from 66 to 70% over the first year to 17% at the end of a 5-yr period (Bruns and Rasmussen 1957). Kiemnec and Larson (1991) found that germination and root growth of L. draba decreased with incremental decreases in osmotic potential, a potential of (1.5 MPa completely inhibiting germination, whereas increasing salt concentrations had no effect on germination or root growth. In a 3Áyr study of weed species in vineyards in Crimea, Ukraine, high seed productivity of L. draba was associated with increased seed quality, such as absolute seed weight and germinability (Kozhevnikova and Mahayeva 1980).…”

Journal of Range Management, Volume 53, Number 5 (September 2000)

“…Hoary cress germination is limited by dry environmental conditions (Kiemnec and Larson 1991). The xeric nature of the sagebrush ecosystem restricts seed germination, emergence, and survival to microsites where moist conditions are present.…”

“…Osmotic potential can also be a factor, especially in arid areas where salt influences are more common. Kiemnec and Larson (1991) reported hoary cress germination rates of 82, 55, 11 and 0% at osmotic potentials of 0, -0.5, -1.0, and -1.5 MPa. The process of soil freezing and thawing may have also benefited germination through vertical redistribution of soil moisture upward toward the freezing layer (Heidmann and Thorud 1976).…”

“…Seed rain occurs as individual seeds are released through ruptures in the capsule sidewall, as individual capsules, and as capsule clusters which break away from the parent plant. Hoary cress seed exude mucilage when moistened (Kiemnec and Larson 1991). Mucilage produced by other species increases germination under conditions of low osmotic potential (0 to -0.2 MPa) (Harper and Benton 1966).…”