The effects of fluometuron on the ultrastructural development,chlorophyll accumulation and photosynthetic competence in developing velvetleaf seedlings |
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| Authors: | William P Wergin John R Potter |
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| Institution: | Agricultural Research Service, U. S. Department of Agriculture USA |
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| Abstract: | Velvetleaf (Abutilon theophrasti L.) seedlings were germinated in the presence of 0, 5, 10 or 80 μg/ml 1,1-dimethyl-3-(α,α,α-trifluoro-m-tolyl)urea (fluometuron). The development of chloroplasts in the mesophyll tissue of the cotyledons was examined with the electron microscope and correlated with the accumulation of chlorophyll and the attainment of photosynthetic competence in 2- to 7-day-old seedlings. The formation of prolamellar bodies and their subsequent transformations into primary thylakoids were not prevented by fluometuron. However, membrane fusion into normal grana was altered by treatments containing this herbicide. Increasing the concentration of fluometuron reduced the number and length of stroma lamellae and promoted more elongate grana with fewer compartments. In addition to these structural changes, the seedlings treated with 5 μg/ml fluometuron accumulated only 50% of the chlorophyll that was present in the controls but remained green until necrosis developed. At 10 μg/ml, the seedlings exhibited a 75% reduction in chlorophyll content and became photobleached by the seventh day and treatment with 80 μg/ml resulted in only a trace of chlorophyll in the cotyledons and the albinistic appearance of seedlings. Net photosynthesis was completely inhibited by all treatments containing fluometuron. These observations indicate that in addition to being a Hill reaction inhibitor, fluometuron treatment directly alters the normal development of internal chloroplast membranes. |
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