Rice and weed competition for resources
1990
Pamplona, R.R. | Dingkuhn, M. | Ampong-Ngarko, K. | De Datta, S.K. (International Rice Research Inst., Los Banos, Laguna (Philippines))
Effective and ecologically responsible control of weeds in rice fields requires a good physiological understanding of the species involved and their interaction in the use of resources. Greenhouse experiments during the 1989 wet season studied the leaf net photosynthesis (A), respiration (R), quantum efficiency (QE), water use efficiency (WUE), chlorophyll content, and the response of these parameters to shade in ten weed species (Echinochloa crus-galli (L.) P. Beauv., E. colona (L.) Link, Rottboellia cochinchinensis (Lour.) W.D. Clayton, Eleusine indica (L.) Gaertn., Paspalum distichum L., Leersia hexandra Sev., Ischaemum rugosum Salisb., Cyperus rotundus L., C. difformis and Scirpus maritimus (L.)) and two rice cultivars (IR64 and Kinandang Patong). Competition for light, water, and nitrogen between the weed R. cochinchinensis and Kinandang Patong rice under different degrees of shading was studied in the field. Resource use efficiencies of C4 plants (among them, most weeds) were superior to those of C3 plants (among them, rice). Within each group, contrasting ecophysiological strategies were realized. Shade acclimation generally resulted in higher leaf width and chlorophyll content, higher QE and A at low light, and reduced R and light compensation point. WUE was only slightly affected by shade. R. cochinchinensis outperformed rice irrespective of N and shade environment due to its higher resource use rates and efficiencies. Differences in shade acclimation among the rice cultivars appeared sufficient to justify further varietal studies with the prospect of identifying genetic traits that increase competitiveness in resource use and enable sustainable rice production.
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