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

• Published in: Weed biology and management 2003-03, Vol.3 (1), p.8-14
• Main Authors: Bakar, B.H. (University of Malaya, Kuala Lumpur (Malaysia)), Nabi, L.N.A
• Format: Article
• Language: English
• Subjects: chemical media; GERMINATION; ISCHAEMUM; Ischaemum rugosum; Ischaemum rugosum Salisb; mortality; ORYZA SATIVA; PLANT ESTABLISHMENT; seedling growth; survivorship; temperature and light regimes
• ISSN: 1444-6162; 1445-6664
• DOI: 10.1046/j.1445-6664.2003.00075.x

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 KNO3, 5% H2O2 or 0.01 m HNO3, and incubated under continuous darkness. Seeds treated with 5% H2O2 at 30°C, or oven‐dried and treated with 0.01% M HNO3 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 KNO3, H2O2 or HNO3 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.