Germination of field dodder (Cuscuta campestris Yunck.) was investigated in field and laboratory studies. Germination plots established to simulate field conditions showed a rapid decline in the number of seedlings emerging over a 5-yr period. Less than 10% of the seeds planted emerged. Time of germination was correlated with temperature. The dormancy of seeds buried at various depths was found to be broken by overwintering. Older seeds and those close to the surface germinated best. Scarified seeds did not germinate at 15 C nor at temperatures of 39 C or above. Maximum germination occurred at 30 and 33 C. Scarified seeds planted at various depths failed to emerge from 3.8, 4.0, or 7.6 cm in the three soil types evaluated; the majority emerged from 3 cm or less. Seeds stored outdoors, at 3 to 8 C, or −3 to 0 C declined in dormancy with time compared to seeds stored at 15 to 25 C.

The effects of chloracetamides on protein synthesis were studied both in vivo and in vitro. Four chloracetamide herbicides, alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide], metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide], CDAA (N–N-diallyl-2-chloroacetamide), and propachlor (2-chloro-N-isopropylacetanilide) were tested for inhibition of [3H]-leucine incorporation into protein. Incorporation of 3H-leucine into trichloroacetic acid (TCA)-insoluble protein was inhibited in oat (Avena sativa L. ‘Victory’) seedlings grown in sand culture and treated 12 h at 1 × 10−4M with these chloracetamides. The herbicides were also tested in a cell-free protein synthesizing system containing polyribosomes purified from oat root cytoplasm. These herbicides had no effect on the rates of polypeptide elongation nor on the synthesis of specific polypeptides when herbicides (1 × 10−4M) were added directly to the system. Polypeptide formation was inhibited 89% when 1 × 10−4M cycloheximide was added during translation. Cytoplasmic polyribosomes were isolated from oat roots treated 12 h with 1 × 10−4M herbicide. Translation rates and products were not altered when these polyribosomes were added to the in vitro system. Protein synthesis is inhibited when tested in an in vivo system; however, the inhibition does not occur during the translation of mRNA into protein.

A field experiment involving seven cultural practices was begun in 1974 in an area heavily infested with velvetleaf (Abutilon theophrasti Medic.) seed. Our objective was to determine the time required to eradicate velvetleaf seed from the soil. This paper reports the results of the first 4 yr of a long-term study. A cultural practice is repeated on the same plot year after year. Since the experiment was begun, no velvetleaf plants have been allowed to produce seed in any plots. The number of viable velvetleaf seeds is monitored by yearly soil sampling. In 1978, after 4 yr of a fallow treatment involving intensive tillage (two plowings per yr plus monthly tillage throughout the growing season), only 10% of the original seed population remained. However, that 10% was 1,300 viable seeds per m2 (to a depth of 23 cm). Four other practices that involved tillage gave generally similar results. Under undisturbed, continuous alfalfa, 56% of the original seed population remained after 4 yr, and under undisturbed, continuous chemical fallow, 37% remained. The results thus far demonstrate the extreme difficulty of eradicating velvetleaf seeds from the soil, and generally agree with reports in the literature, which primarily include studies conducted under more artificial conditions than we used. Our results also suggest that, in soil, velvetleaf seeds that have become water permeable (nonhard) may later again become water impermeable (hard).

Four flower-color phenotypes were observed in a population of musk thistle (Carduus thoermeri Weinm.). This plant has been commonly referred to as C. nutans L. The four phenotypes were: purple corolla and purple pollen, pink corolla and white pollen, white corolla and purple pollen, and white corolla and white pollen. In four generations, 177 self-pollinated individuals of these four phenotypes produced 2123 progeny plants that were classified. Results support the hypothesis that three independent gene pairs were involved in determining the four flower phenotypes. The gene pairs have been designated P/p, W/w, and Pi/pi. It was postulated that all three dominant alleles, P, W, and Pi, must be present to produce both purple corollas and purple pollen. The p allele prevents color development in both corollas and pollen; the w allele eliminates color in corollas but does not affect pollen color; and the pi allele dilutes corolla color from purple to pink and eliminates pollen color. Height measurements of progenies of self-pollinated plants indicated that decreased plant height was associated with inbreeding. On the basis of the evidence presented, the musk thistle plants used in these experiments appear to belong to a single species.

Absorption and translocation of buthidazole [3-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-4-hydroxy-1-methyl-2-imidazolidinone] was determined in several plant tissues. Buthidazole caused slight effects on seed germination. Germination of soybean (Glycine max L. Merr. ‘Williams’) seeds was inhibited up to 15% and velvetleaf (Abutilon theophrasti Medic.) was stimulated up to 13%. Buthidazole was absorbed by germinating soybeans, velvetleaf, and corn (Zea mays L.) with rate of absorption increasing when roots were capable of absorption. Buthidazole concentrations of 0.5 μM or greater inhibited growth of soybean in the early second-trifoliolate growth stage when supplied to the roots in nutrient solution. Within 96 h, 29% of the buthidazole available to soybeans was absorbed from nutrient solution and 89% of that absorbed was found in the shoots. The expanded leaves of soybean accumulated the majority of the radioactivity. Radioactivity in roots of soybean approached a steady state condition within 96 h, whereas 14C continued to increase in shoots. Foliar absorption of buthidazole in soybean greatly increased when any one of several surfactants were used. Soybean dry weight reduction nearly doubled by adding surfactants. Over 60% of the 14C-buthidazole applied to soybean leaves was absorbed within 1.5 h, and increased to 73% by 96 h when the nonionic surfactant, AL-411-F3 [Phytobland Spray Oil (83%) plus ATPLUS 300F (17%)] was used compared to only 7% in 96 h without the surfactant. There was little or no movement of buthidazole from the treated leaves. Translocation was typical of apoplastic movement.

Hexazinone [3-cyclohexyl-6-(dimethylamino)-1-methyl-1,3,5-triazine-2,4(1H,3H)-dione] was applied to honeylocust (Gleditsia triacanthos L.), honey mesquite [Prosopis juliflora (Swartz) DC. var. glandulosa (Torr.) Cockerell], huisache [Acacia farnesiana (L.) Willd.], live oak (Quercus virginiana Mill.), Macartney rose (Rosa bracteata Wendl.), post oak (Quercus stellata Wangenh.), saw greenbrier (Smilax bona-nox L.), whitebrush (Aloysia lycioides Cham.), and yaupon (Ilex vomitoria Ait.). Bromacil (5-bromo-3-sec-butyl-6-methyluracil) and tebuthiuron {N-[5-(1,1-dimethylethyl)-1,3,4-thiadiazol-2-yl]-N,N′-dimethylurea} were used for comparison in some experiments. Hexazinone was required at the following rates to kill at least 75% of the following species: 1.1 kg/ha for live oak, 2.2 kg/ha for post oak, 4.5 kg/ha for huisache (at Bryan, Texas) and whitebrush, and 9 kg/ha for honeylocust. Hexazinone was ineffective at 9 kg/ha for control of honey mesquite, huisache (at Washington, Texas), Macartney rose, saw greenbrier, and yaupon. Tebuthiuron at 1.1 kg/ha killed 80% of the live oak, and as a subsurface spray at 4.5 kg/ha, killed huisache (at Washington, Texas). Bromacil was effective on huisache at 9 kg/ha.