Warburg experiments indicated that fluometuron-[3-(m-trifluoromethylphenyl)-1,1 -dimethylurea], at rates up to 10 p.p.m., did not affect respiration of cotton or cucumber. Both Warburg and 14C02 fixation studies indicated that fluometuron inhibited photosynthesis by these species. A subsequent

The absorption, translocation, and metabolism of metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H) one] by soybean (Glycine maxMerr. ‘Lee 68′) and hemp sesbania (Sesbania exaltataL.) grown in nutrient solution and in soil treated with14C-metribuzin were investigated. Absorption studies indicated there were no significant differences in the amount of14C-metribuzin absorbed from treated nutrient solution by soybean (tolerant) and hemp sesbania (susceptible). When these species were grown in14C-metribuzin treated soil, hemp sesbania absorbed appreciably more herbicide than did soybean.14C-metribuzin and (or) its14C-metabolites were translocated from the roots to the shoots of both species. Radioactivity was rapidly translocated and accumulated in all the leaves of hemp sesbania, but it tended to accumulate to the greatest extent in the roots and lower leaves of soybean. Translocation differences between the two species were apparent in plants grown either in soil or nutrient solution treated with14C-metribuzin. However, differences were greatest in plants grown in treated soil. Preliminary metabolic studies indicated that a higher rate of metribuzin degradation occurred in soybean than in hemp sesbania. The major14C-metabolite appeared to be the relatively nonphytotoxic deaminated diketo derivative [6-tert-butyl-1,2,4,-triazine-3-5(2H,4H)dione]. Thus, differences in the absorption, translocation, and metabolism of metribuzin all appeared to contribute to the differential susceptibility of soybean and hemp sesbania to metribuzin.

No abstract

The technique of microradioautography was used to study the absorption and translocation ofa,a,a-trifluoro-2,6-dinitro-N,N-dipropyl-p-toluidine (trifluralin) by cotton (Gossypium hirsutumL., var. Coker 201) and soybean (Glycine max(L.) Merr., var. Lee). Radioactivity from14C-trifluralin was retained primarily on the surfaces of the roots of cotton and soybean. This was apparently due to a tenacious adsorption or binding of the radioactivity to the epidermis and cuticle. Entrance of radioactivity into the roots of these species was greatly facilitated by breaks in the epidermis, such as might occur from seedling diseases or mechanical damage. Within the roots, radioactivity was noted in the walls of the xylem vessels and cortical cells. Little movement out of the soybean roots was observed, but limited movement of radioactivity into the leaves of cotton, apparently via the metaxylem, was noted. Radioactivity accumulated in the protoxylem of the cotton stem where many elements appeared to be plugged. Results of this study indicate that care should be used in interpreting data from studies where loss of radioactivity from nutrient media is used as a criterion of herbicide absorption, and where gross radio autography is used as an indicator of herbicide translocation.

Germination studies were conducted on seed of wild poinsettia(Euphorbia heterophyllaL.) collected in 1974 and 1975. Significant differences in germination existed between the seedlots. An alternating temperature regime of 25/35 C was optimum for germination, and no effect of light was noted at this temperature regime. However, light increased germination at temperatures of 25, or 35 C, and decreased it at 10/35 C. Storage of wild poinsettia seeds at 36 C for 2 to 12 weeks caused a significant decrease in dormancy as compared to corresponding storage at 5 C. Seed moisture levels below 7.7% did not seem to affect viability at 5 or 25 C after a storage period of 3 to 9 months. Seed viability decreased rapidly when seed were stored for 3 months at 25 C with a moisture content of 10.8% or at 5 or 25 C with a moisture content of 18.6%. Seeds buried in the fall at a depth of 5 cm germinated extensively in the field 9 months later. Field germination decreased as depth of burial increased.