Mefluidide {N-[2,4-dimethyl-5-[[(trifluoromethyl) sulfonyl] amino] phenyl] acetamide} was evaluated for effects on corn [Zea mays (L.) ‘Pioneer 3535’] coleoptile elongation. Mefluidide at 10-8 M, 10-7 M, and 10-6 M stimulated elongation approximately equal to growth stimulations with 10-6 M indoleacetic acid (IAA). Polar transport of 14C-IAA from donor agar blocks through corn coleoptiles and into receiver agar blocks after 12 h was increased 246% by 10-4 M mefluidide and inhibited 82% by 10-3 M mefluidide. Mefluidide-related chemicals (10-4 M) lacking a trifluoromethyl-sulfonyl-amino chain at the 1-position of the phenyl ring did not alter 14C-IAA transport. IAA transport was increased 97% when the acetamide chain at the 5-position was absent and 255% when the methyl in the 4-position was absent, and it decreased 65% when the methyl at the 2-position was absent. Polar transport of 14C-IAA through soybean [Glycine max (L.) Merr. ‘Williams’] hypocotyls was not altered by 10-4 M mefluidide; however, 10-3 M mefluidide increased IAA transport 116%. After 6 h, corn coleoptiles metabolized 14% of the mefluidide absorbed and soybean metabolized 54% of the mefluidide absorbed from 14C-mefluidide solutions (10-6 M). Differences in the rate of metabolism of mefluidide in meristematic tissue of corn and soybean may explain differences in mefluidide effects on auxin transport in corn and soybean.

As all herbicides act on pathways or processes crucial to plants, in an inhibitory or stimulatory way, low doses of any herbicide might be used to beneficially modulate plant growth, development, or composition. Glyphosate, the most used herbicide in the world, is widely applied at low rates to ripen sugarcane. Low rates of glyphosate also can stimulate plant growth (this effect is called hormesis). When applied at recommended rates for weed control, glyphosate can inhibit rust diseases in glyphosate-resistant wheat and soybean. Fluridone blocks carotenoid biosynthesis by inhibition of phytoene desaturase and is effective in reducing the production of abscisic acid in drought-stressed plants. Among the acetolactate synthase inhibitors, sulfometuron-methyl is widely used to ripen sugarcane and imidazolinones can be used to suppress turf species growth. The application of protoporphyrinogen oxidase inhibitors can trigger plant defenses against pathogens. Glufosinate, a glutamine synthetase inhibitor, is also known to improve the control of plant diseases. Auxin agonists (i.e., dicamba and 2,4-D) are effective, low-cost plant growth regulators. Currently, auxin agonists are still used in tissue cultures to induce somatic embryogenesis and to control fruit ripening, to reduce drop of fruits, to enlarge fruit size, or to extend the harvest period in citrus orchards. At low doses, triazine herbicides stimulate growth through beneficial effects on nitrogen metabolism and through auxin-like effects. Thus, sublethal doses of several herbicides have applications other than weed control.

Broomsedge populations have increased substantially over the last decade on roadsides in Georgia. The invasiveness of this species might have resulted from imazapic use for bermudagrass growth regulation and the limited use of MSMA on roadsides. The objectives of this research were to evaluate (1) differential growth inhibition of bermudagrass and broomsedge to imazapic, (2) susceptibility of isolated acetolactate synthase (ALS) enzymes of bermudagrass and broomsedge to imazapic, (3) broomsedge control with tank mixtures of imazapic with MSMA, and (4) the influence of imazapic on absorption and translocation of 14C-MSMA. In greenhouse experiments, imazapic reduced bermudagrass shoot biomass ~ 2 times more from the nontreated than broomsedge. Isolated ALS enzymes of bermudagrass were ~ 100 times more susceptible to inhibition by imazapic than broomsedge. In field experiments, imazapic provided no control of broomsedge, but MSMA alone controlled broomsedge 81% at 12 mo after initial treatments (MAIT). Broomsedge control was reduced to 45% when MSMA was tank mixed with imazapic at 12 MAIT. In laboratory experiments, imazapic tank mixtures did not reduce broomsedge absorption or translocation of 14C-MSMA. Overall, bermudagrass is more susceptible to imazapic due to greater target-site inhibition than broomsedge. Results emphasize the importance of MSMA use for broomsedge control, but agronomists should avoid tank mixtures with imazapic to reduce potential antagonism.

The relationship between IGF-I and changes in muscle fibre phenotype in response to 6 d of stretch or disuse of the lower limb muscles of the rabbit was studied by combining in situ hybridisation and immunohistochemistry procedures. Passive stretch by plaster cast immobilisation of the muscle in its lengthened position not only induced an increase in IGF-I mRNA expression within the individual muscle fibres but also an increase in the percentage of fibres expressing neonatal and slow myosin. This change in phenotype was also found to be accompanied by a rapid and marked increase of muscle mass, total RNA content as well as IGF-I gene expression. In contrast, IGF-I appears not to be involved in muscle atrophy induced by immobilisation in the shortened position and the inactivity which results from this procedure. The level of increase in expression of IGF-I mRNA varied from fibre to fibre. By using adjacent serial sections, the fibres which expressed IGF-I mRNA at the highest levels were identified as expressing neonatal and the slow type 1 myosin. These data suggest that the expression of IGF-I within individual muscle fibres is correlated not only with hypertrophy but also with the muscle phenotypic adaptation that results from stretch and overload.

Fish Farming enriches the water column in dissolved organic and inorganic material. These materials excreed by the fish, elutriate from uneaten food and derive from other polluting substances. Ratios of the organic/inorganic forms of substances (for example N and P) are thus modified. Such perturbations in turn affect phytoplankton development. From in vitro analyses and tests of water taken from a turbot rearing tank, we show the changes in seawater chemical composition produced as well as the way growth was modified in three phytoplankton species: the diatom, Chaetoceros gracile, and the dinoflagellates, Gymnodinium cf. nagasakiense and Alexandrium minutum. Elutriates from the granules used for feed (0.1 to 100 mg.l−1) were found to be stimulating, particularly for Gymnodinium. Alexandrium was strongly inhibited both by turbot-tank water diluted 10-fold with coastal seawater and by diluted faeces elutriates. Urea added at low concentrations (1 to 2.5 µmol.l−1) inhibited growth in Alexandrium and Chaetoceros, but at 1 µmol.l−1 it stimulated growth in Gymnodinium. The antibiotic, Oxytetracycline was complex in its effects, with growth inhibition being observed in Chaetoceros and Gymnodinium, but stimulation in Alexandrium (at 0.2 mg.l−1). In general, we found fish farming to allow phytoplankton growth, except for Alexandrium in a few cases. Additions to the water from fish farming may regulate growth in some species. As such additions act differently on growth in different species, fish farming is likely to markedly modify species composition in its vicinity.