Germination and Seedling Development of Common Milkweed and Other Species

Abstract

Common milkweed(Asclepias syriacaL.) seed did not survive storage in water for 1, 2, and 12 months at 40, 30, and 5 C, respectively; but under dry storage seed viability was destroyed only at 40 C for 5 months. Stratifying common milkweed seed in water at 5 C was more effective in breaking dormancy than at 22 C. Mechanical scarification also caused a significant increase in germination. Exogenous 6-furfurylamino purine (kinetin) and gibberellic acid-3 (GA) increased germination while indole-3-acetic acid (IAA) had no effect. The optimum germination temperature scheme for common milkweed was an alternating 20 to 30 C, the maximum between 35 and 40 C, and the minimum between 15 and 20 C. Common milkweed seedlings were more susceptible to moisture stress than kochia [Kochia scoparia(L.) Schrad.] but less susceptible than hemp dogbane(Apocynum cannabinumL.) and sunflower(Helianthus annuusL.). In a greenhouse study common milkweed was less drought tolerant than eight other weed species. Common milkweed seedlings tolerated wider pH ranges than honeyvine milkweed [Ampelamus albidus(Nutt.) Britt.], kochia, and sunflower. Common milkweed seedlings were less tolerant to salt solutions than four other species. Common milkweed emerged from 6-cm depths in Sharpsburg silty clay loam (sicl) at 20 or 30 C but only from the 3-cm depth at an alternating 20 to 30 C. Results from root box studies showed that common and honeyvine milkweed produced less shoot and root weight than kochia and sunflower and had a lower growth rate index of roots than sunflower. Common milkweed seedlings resprouted 21 days after planting when clipped at ground level. As days from planting to clipping increased, sprouting activity increased.

Intermediate growth forms as a model for the study of plant clonality functioning: an example with root sprouters

“…Very young seedlings are unable to form adventitious buds on their roots and to sprout, because the ability to root-sprout is connected with sufficient assimilation and the presence of activated meristem tissue (Esau, 1965;Peterson, 1975). Evetts and Burnside (1972) found that injured juveniles of Asclepias syriaca were able to sprout at the age of three weeks. Some injured juveniles of the short-lived herbs Rorippa palustris and Barbarea vulgaris were capable of root-sprouting at the age of four weeks, and 100% regeneration occurred already in six-week old juveniles of these species (Martı´nkova´et al, 2004b).…”

Germination Ecology of Goosegrass (Eleusine indica): An Important Grass Weed of Rainfed Rice

“…Seed germination of goosegrass was not significantly affected by the tested range of pH solutions, and it varied from 92 to 95% over the pH range of 5 to 10 (data not shown). An optimum pH level is required during germination and growth of plants, but many weed species are tolerant of extreme pH levels (Evetts and Burnside 1972). In the case of goosegrass, pH may not be a limiting factor for germination in most soils, which could partly explain its wide range.…”

Influence of soil properties and soil moisture on the efficacy of indaziflam and flumioxazin onKochia scopariaL.

“…Kochia scoparia L. was introduced into the United States from Europe as an ornamental, and escaped cultivation, spreading across cultivated fields, along roadsides and in waste areas throughout the western United States . Kochia germinates early in the spring and tolerates heat, cold, drought, acidic conditions, alkaline conditions and salinity . A single plant can produce up to 15 000 seeds .…”

“…A single plant can produce up to 15 000 seeds . Kochia can germinate at soil moisture potentials between −1320 and −1600 kPa, and is most competitive under dry soil moisture conditions . Herbicide‐resistant kochia has been documented in three countries, to four different sites of action …”

“…5 Kochia can germinate at soil moisture potentials between −1320 and −1600 kPa, and is most competitive under dry soil moisture conditions. 2,4,6 Herbicide-resistant kochia has been documented in three countries, to four different sites of action. 1,7 Efficacy of many pre-emergence (PRE) herbicides used for kochia control varies according to soil physicochemical properties and soil moisture.…”