Seed germination, seedling establishment and growth patterns of wrinklegrass (Ischaemum rugosum Salisb.)

Abstract

Several laboratory and glasshouse experiments were conducted to assess seed germination, seedling establishment and growth patterns of wrinklegrass ( Ischaemum rugosum Salisb.) influenced by temperature and light regimes, and chemical media. Wrinklegrass was a positively photoblastic species, and seed germination was temperature-dependent and light-mediated. Seeds soaked in distilled water for 24 h, or oven-dried at the respective temperature regimes of 15, 20, 25, 30, 35, or 40 ∞ C prior to treatment in distilled water and incubated in darkness, failed to germinate. Likewise, no germination prevailed when the seeds were exposed to similar temperature regimes and treated with 0.2 M KNO 3 , 5% H 2 O 2 or 0.01 M HNO 3 , and incubated under continuous darkness. Seeds treated with 5% H 2 O 2 at 30 ∞ C, or oven-dried and treated with 0.01% M HNO 3 at 35 ∞ C registered 10 and 20% germination. Approximately 75 and 90% of the light-exposed seeds for all treatments germinated in the first three and six days at 25 ∞ C. No germination occurred at 15 ∞ C in the first three days after treatment. Seeds subjected to 40 ∞ C for six days after treatment recorded 36% germination. The optimum temperatures for seed germination were 25-30 ∞ C. Seed drying and soaking treatments widened the windows of the optimal temperatures for wrinklegrass germination. The acidic media of KNO 3 , H 2 O 2 or HNO 3 favored seed germination. Less than 5% of seed germination occurred with burial or water inundation at depths exceeding 2 cm. Seed burial or inundation at ≥ 2 cm depths inhibited seed germination. Seeds sown onto moist paddy soils registered ca. 50% germination. Free-floating seeds on the water surface registered ca. 98% germination within the first six days after seeding. The mean number of seedlings that survived was inversely proportional to water depths, with close to 100% mortality at the 14 cm depths of inundation. Both plant height and seedling survival were linearly proportional to the amount of root mass of seedlings which penetrated the soil. The weed was a prolific seed producer ( ca. 6000 seeds/ genet or 18 000 seeds/genet per year). The vegetative and reproductive efforts of each wrinklegrass plant registered values of 0.68 and 0.32, respectively.

Temperatura e luz na germinação das sementes de apaga-fogo (Alternanthera tenella)

“…A porcentagem máxima de germinação obtida por meio do modelo ajustado foi de 70,17% (Figura 1). Resultados semelhantes foram observados para a espécie Ischaemum rugosum por Bakar & Nabi (2003), os quais observaram maior porcentagem de germinação das sementes em temperaturas entre 25 e 30 ºC. Diversas outras espécies de plantas daninhas de origem tropical tendem a apresentar maior germinação sob temperaturas mais altas.…”

Ecological significance of rice (Oryza sativa) planting density and nitrogen rates in managing the growth and competitive ability of itchgrass (Rottboellia cochinchinensis) in direct-seeded rice systems

“…a)e -bx , fitted to the stem and whole-plant biomass data, where y is the stem and whole-plant biomass at different rice planting densities (plants m -2 ), y0 is the minimum value at rice planting density of 400 plants m -2 , and (y0 ? a) is the maximum value at rice planting density of 0 plants m -2 N (kg ha -1 ) (Bakar and Nabi 2003). suggesting that the weed had a higher capacity for the uptake of N than rice plants, which made the weed more competitive to interfere with the growth of rice.…”

GROWTH AND DEVELOPMENT OF Fimbristylis miliacea (L.)Vahl

“…However, C. esculentus partitioned only 38% of its dry weight to tubers, whereas C. rotundus partitioned 50% of its dry weight to fewer and larger tubers. In the case of I. rogusum, seeds/spike, seed weight/plant (g) and seed number/plant and 1000 seed weight (g) was 57, 24.5, 6000 and 4, respectively (Bakar and Nabi 2003), which indicates much bigger seed size and lower seed number/plant than Fimbristylis miliacea.…”

“…Growth and development study have been observed in several weed species such as Echinochloa crus-galli (Azmi 1994;Itoh 1991;Arifin 2004), Leptochloa chinensis (Pane 1997), Ischaemum rugosum (Bakar and Nabi 2003), Cyperus esculentus and C. rotundus (Williams 1982). Even though, biological study of F. miliacea has been reported to some extent by Burkill (1935) and Holm et al (1977).…”