Broadleaf plant

The potential for environmental contamination continues to come from families of herbicides that have been used for years. The chlorophenoxy herbicides such as 2,4-D (2,4-dichlorophenoxy acetic acid) and 2,4,5-T (2,4,5-trichlorophenoxy-acetic acid) (Figure 5.1) are systemic acting compounds to control broadleaf plants and have been in use since the 1940s. The oral toxicities of these compounds are low. 

Broadleaf seedlings have two leaves as they emerge from the seed. Their leaves are generally broad with netlike veins. Broadleaves usually have a taproot and a relatively coarse root system. All actively growing broadleaf plants have exposed growing points at the end of each stem and in each leaf axil. Perennial broadleaf plants may also have growing points on roots and stems above and below the surface of the soil. Broadleaves contain species with annual, biennial, and perennial life cycles. 

Herbicides are the most important pesticide class in terms of production volume and market value. In agriculture they are used to control weeds. Weeds are unwanted plants, such as grasses, sedges, and broadleaf plants, that compete with the desired crop plants for nutrition, water, and land, thereby reducing the yield. Herbicides also have nonagricultural uses as they help in erasing vegetation on streets, railroad tracks, sports fields, and other public areas. 

MAJOR USES Used for herbicide control on broadleaf plants, grasses, wheat, com, sugarcane, barley, oats, rice, lawns and turf, non-crop areas pasture and jungle defoliation plant growth regulator. 

The life span of turfgrass leaves is very short compared to broadleaf plants [5]. In aging grass leaves, cell contents are translocated to other portions of the plant and the old leaves begin to lose weight. The leaf exhibits a dull grayish appearance, eventually discolors and dies back from the tip to the base. It is important to understand that tip die-back is an inevitable event for all turfgrass leaves. 

Sulfentrazone is a broad-spectrum, pre-emergent herbicide that provides good control over broadleaf weeds, grasses and sedges in crops and turf. The metabolism of sulfentrazone in animals and plants is similar. The major plant metabolite of sulfentrazone is 3-hydroxymethyl sulfentrazone (HMS). The soybean tolerance of 0.05 mg kg includes residues of sulfentrazone plus its major metabolite, HMS. The rotational crop tolerance includes residues of sulfentrazone and its major metabolites, HMS and... 

The broadleaf weeds responded to tillage in the same general manner when rye root residue was present, however, it does appear that the growth of all the weeds was inhibited by the presence of rye root residue. This can be seen in Table II by comparing results from the tilled treatment with and without rye root residue. In the case of common ragweed, biomass was reduced 34% (178.3 g no rye, till versus 118.3 remove mulch till), but the density increased by 69% (140 plants/2.2 m versus 280 plants/2.2 m ) when rye root... 

Crabgrass control in the mulched plots was generally lower than the control of broadleaf species, despite the alachlor treatment at planting time (Table VI). Poor crabgrass control in the non-tilled treatments may have been due to the low early season rainfall which reduced the effectiveness of alachlor. 

Dicamba (3,6-dichloro-2-methoxybenzoic acid) is primarily used as a postemergence broadleaf herbicide, which interferes with normal plant auxin function, subsequently causing uncontrolled growth and the inhibition of the phototropic and geotropic function. Cumulative response results in plant death. The success of auxinic analogues such as Dicamba and 2,4-dichloropheno-xyacetic acid in weed control has led to widespread manufacturing and use. Estimated U.S. production for Dicamba was 5 million kg in 1990 [391]. 

This application was made between 0700 and 0830 a.m. in cool (air temp., 10 0 clear and windless weather. Both granular and emulsion formulations were incorporated to the 7.5cm depth with a disc cultivator within 15 minutes of application. A second cultivation to the same depth, but at right angles to the first, was completed within 2-3 hours. On May 20th both plots were spring-tooth harrowed for seed-bed preparation for soybean planting on the same day. The only subsequent soil disturbance was a row cultivation in late June to control a severe infestation of quack-grass control of broadleaf weeds was essentially complete with the trifluralin. 

Tobacco use is primarily due to psychopharmacological effects of nicotine (Henningfleld et al. 2006). Nicotine is a tobacco alkaloid, a basic substance that contains a cychc nitrogenous nucleus. In Nicotiana plants, most alkaloids are 3-pyridyl derivatives In cured leaf of Maryland Robinson Medium Broadleaf, 24 pyridine derivatives were identified, including nicotine, nomicotine, anabasine, oxynicotine, myosmine, 3-acetylpyridine, 2,3 -dipyridyl, iticotinamide, anatabine, nicotinic acid, and unidentified pyridine alkaloids of derivatives thereof (Tso 1990). Nicotine is the principal alkaloid in commercial tobacco (this was confirmed in 34 out of 65 Nicotiana species) nomicotine, rather than nicotine, appears to be the main alkaloid in 19 out of 65 species and anabasine is the third most important. In addition to the above-mentioned principal and minor alkaloids, the presence of many trace amounts of new alkaloids or their derivatives were frequently reported, including, for example, 2.4 -dipyridyl, 4,4 -dipyridyl, N -formylanabasine, A -formylanatabine, N -acetylanatabine, N -hexanoyl-nomicotine, N -octanoyl-nomicotine, T-(6-hydroxyoctanoyl) nomicotine, and l -(7-hydroxyoctanoyl) nor-nicotine. 

These materials seem best adapted for deweeding coniferous tree species, such as pines and junipers, which have considerable resistance to the oil sprays. Broadleaf species such as elm and walnut are seriously damaged or killed by moderate dosages of the oil sprays, and much research is needed to find if any of this group of plants are sufficiently resistant to warrant use of the mineral spirits as a selective herbicide. 

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