| Greenhouse and laboratory studies were conducted to investigate the effects of: (a) oxyfluorfen {lcub}2-chloro-1-(3-ethoxy-4-nitrophenoxy)-4-(trifluoromethyl) benzene{rcub} on seeds and one- to six-week-old seedlings of loblolly pine and sweetgum; (b) soil incorporated diphenylethers on shoot growth of loblolly, sweetgum, and oat (Avena sativa L.); (c) environmental conditions and formulation of oxyfluorfen and bifenox {lcub}methyl-5-(2,4-dichlorophenoxy)-2-nitrobenzoate{rcub} on emergence and mortality of loblolly pine; and (d) selected herbicides on photosynthesis of loblolly pine cotyledon tissue.; Oxyfluorfen injured the apical meristem of sweetgum at all ages tested but meristems of pine seedlings older than two weeks were not adversely affected. Newly-formed tissues of both species at all ages were injured while older tissues showed tolerance. Time required to develop tolerance varied with species. Loblolly acquired tolerance after two weeks while six-week-old sweetgum were still susceptible. Tolerance of sweetgum cotyledons to oxyfluorfen was correlated with epicuticular wax formation. Results from this study suggest that the primary barrier to foliar penetration of oxyfluorfen is the epicuticular wax layer.; Loblolly was tolerant of soil-incorporated oxyfluorfen, bifenox, and diclofop {lcub}2-{lcub}4-(2,4-dichlorophenoxy)phenoxy{rcub}propanoic acid{rcub} while sweetgum was tolerant of diclofop only. Oat was shown to be relatively tolerant of bifenox but was intolerant of oxyfluorfen and diclofop. The GR(,50) values, and the reported half-life of the herbicides, indicate that potential residue buildup of these herbicides should not be sufficient to affect future crops of pine or sweetgum.; Emergence of loblolly pine was not reduced by soil applications of either bifenox or oxyfluorfen. However, mortality resulted from both herbicides when seedlings were in the "succulent" stage of development. Seedlings in this stage were weak, stunted, and developed lesions on the hypocotyl. Temperature, depth of sowing, and speed of germination had no effect on moderating the herbicide injury.; A bioassay was adapted for use in detecting photosynthesis inhibition of loblolly cotyledon tissue. Several herbicides were shown in inhibit photosynthesis. However, at 10('-3)M, bifenox and oxyfluorfen were not inhibitory to photosynthesis. Differences in respiration rate could also be detected with this bioassay. |
