Growth behaviour and leaf morphology of Philippine strains of Sphenoclea zeylanica showing differential response to 2,4-D |
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| Authors: | B L MERCADO S K DE DATTA T R MIGO A M BALTAZAR |
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| Institution: | University of the Philippines at Los Baños, College, Laguna and International Rice Research Institute (IRRI), P.O. Box 933, Manila, Philippines |
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| Abstract: | The germination and growth of three strains of gooseweed (Sphenoclea zeylanica Gaertn.) that showed susceptibility, moderate susceptibility, and tolerance for foliar-applied 2,4-D isobutyl ester were studied in the laboratory and greenhouse. The plants were isolated from samples collected from major rice (Oryza sativa L.) growing areas in the Philippines. The seeds of all three strains possessed dormancy; light stimulated germination but did not completely overcome dormancy. Without N application, stem elongation and leaf production did not differ among the strains. With 60 kg N ha?1, the susceptible and moderately susceptible strains responded better than the tolerant strain, the difference being apparent at 6 weeks after emergence. Measurements of the leaf cuticle showed significant differences among the strains starting at the 8- to the 10-leaf stage, a trend that paralleled their response to 2,4-D. Adding a surfactant to the spray formulation nullified the differential responses. Implications for managing the weed and correlations with current field observations are discussed. |
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