Translocation basipetal

Similiarly variable is the systemic activity of these compounds, that is the translocation in the vascular system of the plant. In this respect, cymoxanil with its very localized distribution, and fosetyl with its fast and strong translocation both acropetally and basipetally, are the extremes (Table IV). From this point of view, fosetyl is the most remarkable structure it is the only commercial pesticide showing effective acropetal and basipetal translocation at normal use rates. 

It is translocated relatively slowly from the leaves to the roots and tubers. Depending on temperature, light intensity and air and soil moisture, translocation proceeds in 4-8 days, the effect being manifested by chlorotic symptoms, which develop in 2-4 weeks into necrosis. Combined with other translocatable herbicides, such as 2,4-D, 2,4-DB or silvex, basipetal translocation and thus herbicidal action can be increased, and regrowth from tubers reduced. 

Herbicide translocated both acro-petally and basipetally within both xylem and phloems... 

Our improvement of this test is based on the incubation of internode sections in the inversed position (9). Under these conditions the substances undergoing test are applied to young auxin-sensitive apical internode tissues and auxin is translocated basipetally toward the zone of curvature (Figure 1). Using this simple improvement the sensitivity of the test to IAA was increased 1,000 times as little as 10 fmoles of IAA can be detected. 

The water solubility of pyroxychlor is low (11 /ig/ml), and it is a moderately volatile compound. It is rapidly absorbed by the plant, presumably due to its high lipophilicity. It has a systemic and curative effect. It is also translocated basipetally in the plant, so that when sprayed on the foliage it gets into the roots and to the site of infection, (Knauss, 1974). It is scarcely effective in vitro, but it provides protection of long duration to the tobacco plant. This is probably due to a bioaccumulation of the active substance in the root system, where the parent compound or its metabolites are persistent. Pyroxychlor is prepared by the chlorination of fused 4-methylpyridine hydrochloride, followed by the reaction of the compound formed with sodium methylate. 

TBA is readily absorbed and translocated by plants. It moves both acropetally and basipetally and causes typical auxin effects in sensitive plants. It strongly inhibits apical growth and leaf formation (Zimmermann and Hitchcock, 1951). It does not cause epinasty in the MCPA-tolerant weeds but stops their growth so that they cannot compete with the crop at the later growth stages. 

On foliar application propham and chlorpropham are not translocated basipetally in the plants (Still and Mansager, 1973). 

Asulam is used pre- and postemergence as a selective herbicide. In plants it is translocated mainly basipetally with the nutrient stream. Absorption through the leaves can be considerably increased with surfactants. 

Fromm and Bauer [36] found that action potentials in maize sieve tubes change phloem translocation. Using macro- and microautoradiography in mature leaves of maize, Fromm and Bauer [36] studied the inhibition of phloem translocation caused by electric and cold shock. They stimulated the leaf tip with ice water and found that the velocity of signal transmission was 3-5cm/s. Upon stimulation, the microelectrode recorded a basipetally propagating action potential with a depolarizing amplitude of 80 mV in the sieve tubes (Fig. 2). During electrical stimulation, the action potential was measured in the sieve-tube system with a speed of 5cm/s. 

Translocation studies with two paraquat-resistant biotypes of Hordeum lepori-num revealed that the basipetal transport of paraquat in resistant H. leporinum was much reduced compared with susceptible plants. It was concluded that the resistance to paraquat was the result of the reduced herbicide translocation out of the treated leaves [76]. One can suppose that also in this species herbicide sequestration may have been the primary cause for the altered long-distance transport. 

In an uptake experiment, over 90% of the radiolabeled pinoxaden was incorporated into the crops within 5 h when treatment solutions were applied in droplets to the adaxial leaf surface of two-leaved plants of barley, winter wheat or durum wheat. After 24 h, about 20% is translocated out of the treated leaf by basipetal movement below the treated area [87]. Cloquintocet does not affect the absorption or the movement of the herbicide within the crop. 

Translocation studies demonstrate that 3 moves in an acropetal and basipetal manner, e.g., the active ingredient taken up by the roots is transported rapidly to the leaves and the translaminar activity results in its efficient transport across the leaf tissues from one surface to the other. 

These results suggest that in the short-term collection method basal and apical receivers should be applied simultaneously. By this means, the acropetal component of the transport system is accounted for and the auxin then delivered to basal receivers probably will give a more accurate measure for the density of the basipetal auxin stream. Moreover, the calculation of the acropetal/basipetal ratio may reflect the polarity of hormone translocation. 

In contrast to the convincing demonstration of a specific basipetal auxin transport system, mostly conflicting results have so far been obtained concerning the translocation of other hormones. 

Gillespie B, Thimann KV (1963) Transport and distribution of auxin during tropistic response. I. The lateral migration of auxin in geotropism. Plant Physiol 38 214-225 Goldsmith MHM (1959) Characteristics of the translocation of indoleacetic acid in the coleoptile of Avena. PhD Thesis, Radcliffe Coll, Cambridge, Mass Goldsmith MHM (1966 a) Movement of indoleacetic acid in coleoptiles of Avena sativa L. II. Suspension of polarity by total inhibition of the basipetal transport. Plant Physiol 41 15-27... 

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