A bstract. Soybean, Glycine max L., and elodea, Elodea canadensis Michx, leaves were exposed to sublethal and lethal temperatures and examined by light microscopy. Loss

Burley tobacco (Nicotiana tabacum L. ‘Kentucky 14′) was grown as a no-tillage crop in 1974 and 1975 by planting tobacco directly into an existing stand of orchardgrass (Dactylis glomerata L.) or rye (Secale cereale L.). Paraquat (1,1′-dimethyl-4,4′bipyridium ion) and glyphosate [N-(phosphonomethyl)glycine] were used to kill existing vegetation. Benefin (N-butyl-N-ethyl-α,α,α-trifluoro-2,6-dinitro-p-toluidine), oryzalin (3,5-dinitro-N4,N4-dipropylsulfaniiamide), metribuzin [4-amino-6-tert-butyl-3-(methylthio)-as-triazin-5(4H)one], and chlorbromuron [3-(4-bromo-3-chlorophenyl), 1-methoxy-1-methylurea] were used to control annual grasses and broadleaf weeds.Glyphosate was generally more effective than paraquat in killing existing vegetation. There was some injury to the tobacco associated with the glyphosate and paraquat treatments, but this was generally confined to those plants which came into contact with the treated herbage. Metribuzin caused severe damage to the tobacco and was discontinued after the first year. Chlorbromuron caused little injury if kept on the surface but injured the tobacco if incorporated by cultivation as in conventional tillage. Benefin and oryzalin caused little or no injury to the tobacco. All four herbicides gave adequate control of annual grasses and broadleaf weeds.

No abstract

Twelve-day-old corn seedlings (Zea mays L. ‘Funk's G-83’) were exposed to thermal conditions (482 C for 125 msec) approximating those used for flame weed control. Tissue dehydration was evident within 1 min after flame application. One hour after flame exposure, the water content of shoot tissues was 6% less than in nonflamed shoots. Transpirational water loss 16 hr after flame application was reduced by 68% when compared to that of nonflamed seedlings. Assimilation of 14CO2 by flamed seedlings, while substantially decreased when compared with that of nonflamed seedlings, continued on a limited basis even in the most severely injured leaf tips.

Corn (Zea mays L. ‘Funk's G-83’) seedling leaves exposed to flame-generated ultra-high temperatures produced in flame cultivation were fixed in glutaraldehyde, post fixed in osmium tetroxide, and embedded in Araldite. In the light microscope, bundle sheath cells of flamed tissue were more heavily stained with Azure II and less vacuolated than were nonflamed cells. Heated mesophyll cells contained swollen, disrupted, and granular chloroplasts. Examination of flamed tissue by electron microscopy revealed granular, dispersed cytaplasm and altered membrane systems. Chloroplast lamellar systems and envelopes, tonoplasts, and plasmalemmas were disintegrated in both bundle sheath and mesophyll cells.