TRANSLOCATION OF AMINOTRIAZOLE AND DALAPON IN AG ROPY RON REPENS (L.) BEAUV.

Summary. Tracer studies using single drops of solutions containing 3–amino-1,2,4–triazole-5–¹⁴C (aminotriazole-¹⁴C) or 2,2–dichloropropionic acid-2–¹⁴C (datapon-¹⁴C) revealed that in couch plants (Agropyron repens (L.) Beauv.) growing under field conditions in the autumn and at the stage where the aerial shoots were 40–50 cm long, both compounds moved in both symplast and apoplast. Dalapon was less mobile in the symplast than aminotriazole and only negligible amounts of dalapon were translocated to the rhizomes. The nodes of the treated shoots appeared to act as barriers to translocation, a phenomenon more pronounced for dalapon than for aminotriazole.
Application to a basal green leaf led to a more uniform distribution of the compounds within plants and rhizomes than when the application was made to the youngest fully-expanded leaf.
In couch plants with aerial shoots 10–15 cm long treated in the stubble, the distribution of both aminotriazole and dalapon was mainly restricted to the treated shoots. Even 15 days after application only trace amounts of radioactivity could be found in the rhizomes and untreated shoots.     

THE INTERRELATIONSHIP BETWEEN TILLERS AND RHIZOMES OF POA PRATENSIS L.—AN AUTORADIOGRAPHIC STUDY

Summary. The main shoot or selected tillers of seedling plants of Poa pratensis L. were supplied with ¹⁴CO₂ and the distribution of ¹⁴C-assimilates was followed by autoradiography. The primary tillers were initially supplied with ¹⁴C-assimilates from the main shoot but, once established, became independent of the parental shoot for carbohydrates. Similarly, developing rhizome-tillers were supported by the main shoot and established primary tillers but soon became self-supporting, Defoliation of all the tillers of the plant but one led to the defoliated primary and rhizome tillers being supplied with radiocarbon from the remaining intact shoot. Thus, although the primary tillers and rhizome-tillers in the intact plant appear to be physiologically independent, the entire tiller-rhizome system may be re-integrated after defoliation, allowing assimilate redistribution. P. pratensis may be regarded as a convenient link between the non-weedy herbage grasses which generally lack rhizomes and the weedy rhizomatous grasses typified by Agropyron repens (L.) Beauv.
Etat des relations entre les talles et les rhizomes de Poa pratensis L. Etude autoradiographique     

THE EFFECT OF SIMAZINE ON THE PHOTOFIXATION OF CO2 AND ON TRANSLOCATION OF ASSIMILATES IN NORWAY SPRUCE (PICEA ABIES)

Summary. A method of exposing seedlings of Norway spruce (Picea abies (L.) Karst.) to ¹⁴CO₂ is described. Within the 1st hr alter ¹⁴CO₂ exposure, no translocation of the ¹⁴C out of the treated branch could be observed. After a 24-hr period, however, the ¹⁴C in dormant seedlings had been translocated basipetally to part of the root system only, with no lateral diffusion of the ¹⁴C-compounds in the stem. About a week after exposure, both symplastic and apoplastic patterns of translocation had caused a more uniform distribution of ¹⁴C. In seedlings at active internode elongation, the translocation patterns were fundamentally identical to those in dormant seedlings, but the active shoot growth had led to a more uniform distribution of the ¹⁴C.
Simazine at 20 ppm had apparently stimulated both the photofixation of ¹⁴CO₂ and the rate of translocation of the ¹⁴C-assimilates. At 30 ppm, however, simazine had blocked the translocation of nutrients to the roots. On the other hand, the ¹⁴CO₂ uptake was not influenced. The simazine incubation had apparently no influence on the synthesis of cationic photosynthate.     

AGROPYRON REPENS (L.) BEAUV.—SOME EFFECTS OF RHIZOME FRAGMENTATION, RHIZOME BURIAL AND DEFOLIATION

Summary. A factorial experiment with couch grass ( Agropyron repens (L.) Beauv.) grown in boxes examined the effects of rhizome fragmentation, planting depth and shoot removal on the survival of rhizome pieces, new rhizome growth and rhizome carbohydrate reserves.
Burial to 4 in. depth in sandy loam soil led to the death of 54% of 1 in. long rhizome pieces and 28% of 3 in. pieces. With all the segment lengths tested deeper planting decreased the proportion of buds which produced shoots.
Shoot removal every 14 days decreased the dry weight and carbohydrate content of the planted rhizomes and prevented new rhizome growth. Segments 1 or 3 in. long lost their carbohydrate reserves more quickly than 9 in. pieces. Rhizomes planted at 4 in. depth contained less carbohydrate after establishment than shallow-planted material, and produced less new rhizome growth.
IS Agropyron repens (L.) Beauv.–Quelques effets de la fragmentation et de l'enfouissement du rhizome et de la defoliation     

Differential susceptibility of barnyard grass (Echinochloa crus-galli var. crus-galli) ecotypes to Exserohilum longirostratum

Ten barnyard grass ( Echinochloa crus-galli var. crus-galli ) ecotypes collected from several locations in Malaysian and Indonesian granaries were tested for variation in their susceptibility to the leaf blight pathogen ( Exserohilum longirostratum ). Four phenological growth stages of the ecotypes were sprayed with E. longirostratum at the rate of 1 × 10⁷ conidia mL⁻¹ under glasshouse conditions. The results of the study showed that plants inoculated with 1 × 10⁷ conidia mL⁻¹ and exposed for 24 h dew periods were severely infected and the percentage dry weight reduction of all ecotypes significantly increased. The 1–2 and 2–3-leaf stage plants were completely killed within 6 days after inoculation. However, susceptibility reactions among the ecotypes were observed at the 4–5-leaf stage, while the 6–7-leaf stage was resistant. The ecotypes, K-02, PK-04, KN-02, CJ-01, and L-01, were the most susceptible ecotypes as indicated by a higher area under disease progress curve value. The apparent disease progress rates for these ecotypes were significantly faster compared to the other ecotypes. The dry weight reduction among the four growth stages was variable. These findings show that the 1–2 and 2–3-leaf stages are the most susceptible, while the 6–7-leaf stage was resistant. This study has confirmed that a variable response to the fungal pathogen occurred within an intraspecific barnyard grass collection.     

EFFECT OF 2,4-D AND PICLORAM ON TRANSLOCATION OF 14C-ASSIMILATES IN VITIS VINIEERA L.

Summary. High concentrations of 2,4-D and picloram interfered with the downward movement of ¹⁴c-assimilates infield-grown vines. The interference in translocation was appreciably greater with picloram than it was with 2,4-D, Although basipetal translocation was retarded, translocation within the treated shoots continued from the vegetative part to the clusters. Translocation of 2,4-D appeared to follow the same route as ¹⁴c-assimilatcs for the most part. Formative effects were absent on untreated grape shoots although the adjacent shoots treated with 2,4-D or picloram on the same cordons were killed; however, formative effects were evident on some of the stump sprouts which developed after the vines were harvested. The malformed leaves on the stump sprouts were twelve or more nodes from the base of the shoots, while ¹⁴c was in the more basal leaves.
Thompson Seedless (Sultanina) rootings treated with 20 000 ppm 2,4-D or picloram transported less ¹⁴C to the roots than did the controls. Treatment with either herbicide resulted in a marked increase in the labelling of the stems.
Effet du 2,4-D et du pichlorame sur la migration de métabolites marqués au ¹⁴C dans Vitis vinifera L.     

STUDIES ON THE TRANSLOCATION IN AGROPYRON REPENS OF 14C-LABELLED 2,2-DICHLOROPROPIONIC ACID

Summary. Previous findings suggested that the translocation in Agropyron repens of 2,2-dichloropropionic acid (dalapon) may be considerably affected by the transpiration rate. This relationship has been studied further in the present investigation using ¹⁴C-labelled material and autoradiography.
It was found that when dalapon was applied to the leaves and the treated plants were placed in darkness a reduction in the transpiration rate of ca. 90% was associated with a marked increase in the amount of dalapon translocation into the roots and tillers. The evidence provided by the autoradiographs was confirmed by a quantitative assay of the ¹⁴C present in the roots. It was also found, however, that translocation was not appreciably affected either by a 50% reduction in the light intensity or when the transpiration rate was reduced by placing the plaints under conditions of high humidity in the light or by the application of white petroleum jelly to the leaves. An alternative hypothesis, namely that the effect of darkness on the movement of the herbicide might be due to changes induced in the normal pattern of assimilate translocation was also investigated but was not supported by the results obtained. Further experimentss, in which various parts of the treated shoot were placed in the dark, suggested that the effect of darkness on the translocation of dalapon is exerted primarily on the treated leaf itself.
Etudes sur to migration dans Agropyron repens de l'acide 2,2-dichloropropionique marqué avec ¹⁴C     

MOVEMENT AND FATE OF FLUORODIFEN-1'-14C IN CUCUMBER SEEDLINGS

Summary. Autoradiographs and liquid scintillation counts of cucumber ( Cucumis sativus L. cv. Ashley) seedlings indicated rapid absorption and translocation of radioactivity from fluorodifen-1'-¹⁴C ( p -nitrophenyl-α,α,α-trifluoro-2-nitro- p -tolyl ether labelled with ¹⁴C in the 1 position of the p -nitrophenyl ring). After 24 h in 1 mg/1 of fluoro-difen-1'-¹⁴C, 25% of the absorbed radioactivity was translocated from the roots.
Cucumber seedlings degraded fluorodifen-1'-¹⁴C via a pathway similar to that reported for peanut seedlings but at a slower rate. The major degradation products were p -nitrophenol and an unidentified polar compound (Unknown I). More rapid absorption and translocation coupled with slower degradation by cucumber as compared with peanut seedlings are factors which may contribute to the susceptibility of cucumber to fluorodifen.     

Distribution of 14C-glyphosate in legumes parasitised by Orobanche crenata

Absorption and translocation of ¹⁴C-glyphosate was evaluated under controlled conditions in peas ( Pisum sativum L.) and broad beans ( Vicia faba L.) parasitised or not by crenate broomrape Orobanche crenata Forsk.). Absorption increased with time up to 12 days after treatment, and reached about 50% of the ¹⁴C-glyphosate applied. Three days after treatment 70–85% of the total herbicide absorbed had been translocated out of the treated leaflet. There was no consistent differ ence in absorption and translocation between infected and non-infected plants 12 days after treatment. The ¹⁴C-glyphosate concentration in the root system increased with time in broad beans. In peas it remained more or less constant from 3 days after treatment. Generally, pods were stronger sinks for glyphosate than other parts of the plant. Herbicide accumulation in broomrape increased with its growth stage, and the parasite was a much stronger sink for glyphosate than the legume root system.     

AMINOTRIAZOLE METABOLISM IN CIRSIUM ARVENSE (L.) SCOP. AND PISUM SATIVUM L.

Summary. Excised leaves as well as intact plants of Canada thistle ( Cirsium arvense (L.) Scop.) metabolized 3-amino-l,2,4-triazole (aminotriazole) to three major products, Unknowns II, 1a and 1b. Unknown II was identical to β-(3-amino-l,2,4-triazolyl-l-)α-alanine. Unknowns 1a and 1b, previously described as one product, were separated by electrophoresis and thin layer chromatography. Unknown 1a appeared to be a metabolic product of Unknown II while Unknown 1B was derived from Unknown 1a. An enzyme preparation from pea ( Pisum sativum L. cv . Thompson Laxton) seedlings capable of synthesizing tryptophan from indole and serine was also able to metabolize aminotriazole. Tryptophan synthesis with the enzyme preparation was inhibited by aminotriazole and evidence suggests that aminotriazole metabolism may follow a similar pathway to tryptophan synthesis.
Métabolisme de l'aminotriazole chez Cirsium arvense (L.) Scop, et Pisum sativum L.     

3,4,3',4'-RACHLOROAZOBENZENE: ITS TRANS-LOCATION AND METABOLISM IN RICE PLANTS

Summary. 3,4,3',4'-Tetrachloroazobenzene (TCAB) and TCAB-¹⁴C were supplied to the roots of rice ( Oryza sativa L.) plants in nutrient solution. An analysis of the shoots indicated that the TCAB was absorbed and translocated to the shoots. The translocated material was characterized by gas-liquid chromatography and mass spectrometry. Roots were exposed to saturation concentrations of TCAB-¹⁴C in liquid culture to determine the translocation and distribution of the compound. Only 5'6% of the total azobenzene present in the nutrient solution was absorbed by the intact rice plants and only 3'2% of the absorbed TCAB-¹⁴C was translocated to the shoots after 12 days of treatment. No TGAB was isolated from plants treated with propanil or 3,4-dichloroaniline after 14 days of treatment.     

THE TRANSLOCATION AND DISTRIBUTION OF THREE LABELLED HERBICIDES IN PASPALUM DISTICHUM L.

Summary Plants of Paspalum distichum L. with two stolons growing over water were treated separately with the sodium salt of 2,2-dichloropropionic acid-³⁶C1 (dalapon), 3-amino-1,2,4-triazole-¹⁴C (amitrole) and 1,1'-dimethyl-4,4'-dipyridylium dichloride-¹⁴C (paraquat) at four different situations on one stolon. Autoradiographs showed that both the amitrole and dalapon label accumulated in the apices of the treated stolons and in some of the young shoots growing from the base of the plant. The ¹⁴C from the paraquat label showed predominantly xylem translocating with no apical accumulation and little basal translocation. The results indicate that young basal shoots rely to some extent on assimilates from the mature stolons but that there is little transport between mature stolons.
La migration et la distribution de trois Herbicides marqués dans Paspalum distichum L.     

Root exudation of diclofop-methyl and triasulfuron from foliar-treated durum wheat and ryegrass

In this study, we evaluated the release of diclofop-methyl and triasulfuron from the roots of foliar-treated ryegrass and wheat. The study with ¹⁴C-diclofop-methyl indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass. No root exudation from ¹⁴C-diclofop-methyl-treated wheat plants was observed, while 20 days after treatment (DAT) 0.2–0.9% of radioactivity absorbed by ryegrass was found exuded in the growing medium. Root exudation was stimulated three to six times by the presence of untreated wheat or ryegrass sharing the growing medium with diclofop-methyl-treated ryegrass. No subsequent uptake of exuded radiolabel by untreated plants (ryegrass or wheat) in the same pot with ¹⁴C-diclofop-methyl-treated ryegrass was observed. The study with ¹⁴C-triasulfuron indicated a basipetal translocation of foliar-applied herbicide in wheat and ryegrass and also into the growing medium. By 20 DAT, 0.5–4.2% of radioactivity absorbed by wheat or ryegrass was found exuded in the growing medium. The presence of untreated plants (wheat or ryegrass) in the same pot as triasulfuron-treated ryegrass or wheat induced exudation seven to 32 times more. The study also revealed a subsequent uptake of exuded compounds by untreated wheat or ryegrass sharing the medium of ¹⁴C-triasulfuron-treated plants. This study has demonstrated for the first time that the root exudation of exogenous compounds can be related to plant arrangement in pots. The implication is that herbicide root exudation and transfer, a form of allelopathy, could be significant in the field. A precise estimation of environmental fate, unexpected ecological side effects and residual activity of herbicides may require quantification of such exudation.     

AN AUTORADIOGRAPHIC STUDY OF THE MOVEMENT OF 14C-LABELLED ASSIMILATES IN THE DEVELOPING WHEAT PLANT

Summary. ¹⁴CO₂ together with autoradiographic techniques was used to stuy the movement of labelled carbon within wheat plants at different stages in their development. Movement of ¹⁴C about the plain was found to be extensive in the early stages, gradually bccoming more localized until at a stage after ear emergence there was little transference of labelled carbon between tillers within a 24-hour period.
In the early stages of development ¹⁴C from leaves on the main shoot was transported throughout the plant but accumulated in greatest amounts in the meristematic regions. Assimilates produced by the leaves of newly formed tillers were distributed mainly to the meristematic regions of those tillers although labelled carbon was moved in into the rest of the plant. In the later stages of development of each tiller the labelled assimilate was restricted to the tiller itself and to any very young tillers associated with it. After car emergence the pattern of distribution of the labelled carbon from the youngest and second youngest leaves was found to differ. Movement was predominantly towards the ear from the flag leaf and towards the root system from the leaf below the flag.
It was noticed that mature leaves accumulated some labelled material and the possibility that this occurred via the transpiration stream following migration from phloem to xylem, as is the case with some of the case with some of the translocated herbicides, was investigated, but no indication of xylem transference was obtained.
The possible application of these studies to investigations into the relationship between the movement natural assimilates and of translocated herbicides is discussed.     

Effects of formulation and environment on absorption and translocation of clopyralid in Cirsium arvense (L.) Scop. and Polygonum convolvulus L

The patterns of absorption and translocation of ¹⁴C clopyralid commercially formulated as the acid, monoethanolamine salt, potassium salt, 2-ethylhexyl ester and 1 -decyl ester were compared in Cirsium arvense and Polygonum convolvulus grown under three environmental regimes. Plants were grown under a 35% or 65% RH regime in silica sand maintained at 33% w/w moisture or under a water stress regime at 65% RH. Approxi mately 26,39,86,93 and 100% of the applied ¹⁴C-activity from the 2-ethylhexyl ester, acid, monoethanolamine salt, 1-decyl ester and potas sium salt, respectively, were recovered 72 h after application to glass cover slips placed in the growth room. However, loss of applied ¹⁴C-activity after application of the five formulations to both plant species was significant only for the 2-ethylhexyl ester. Regardless of environmental regime, the acid was the most readily absorbed formulation. In contrast to the acid, the salts and esters were less readily absorbed. When the data were expressed as a percentage of absorbed radioactivity, there was no significant difference in translocation when the acid, monoethanolamine salt and potassium salt were compared. However, significantly smaller quantities of the absorbed 2-ethylhexyl and 1-decyl ester were exported from the treated leaf. These results indicate that once absorbed, the esters do not readily partition out of the cuticle, whereas the acid and two salts move into the symplast for subsequent translocation. When the results of the three environmental regimes were compared, the absorption of the monoethanolamine and potas sium salts were greatly reduced under low humi dity or water stress, whereas the acid and esters were not affected.     

Control of Cirsium arvense (L) Scop, by herbicides and mowing

The efficacy of mowing and of herbicides (applied by spot spraying or boom spraying) for the selective control of Cirsium arvense (L) Scop, in Victorian pastures was investigated. The pastures were based on Trifolium repens L. and Lolium perenne L. A general decline in the number of thistle shoots in untreated plots at three out of five sites was recorded.‘Tordon 50-d' (5% a.i. picloram and 20% a.i. 2,4-D as triisopropanolamine salts), MCPB, 2,4-DB and mowing resulted in suppression, but not eradication, during the experimental period. MCPB and 2,4-DB are the most suitable herbicides for selective control. The use of‘Tordon 50-d' is restricted by its effect on clovers, soil persistence and cost. Variable growth of C. arvense, associated with variable summer rainfall in Victoria, increases the difficulty in controlling this weed and necessitates a persistent long term approach.     

Uptake and metabolism of hexazinone in Rubus hispidus L. and Pyrus melanocarpa (Michx.) Willd

Rooted cuttings of Pyrus melanocarpa (Michx.) Willd. had a 3.5-fold greater tolerance to soil-applied hexazinone than those of Rubus hispidus L. in a greenhouse trial. R. hispidus accumulated four times more ¹⁴C-label in the foliage following root uptake of ¹⁴C-hexazinone than P. melano-carpa . Here, the greater uptake and susceptibility of R. hispidus was related to its greater root:fol-iage (weight) ratio compared to the tolerant P. melanocarpa . However, in whole plant metabolism studies employing younger plants there were no differences in ¹⁴C accumulation in the leaves. Here ¹⁴Chexazinone was converted to a number of hydroxylated and/or demethylated triazinone metabolites in both species following vacuum infiltration into leaf disks and root sections, or following root uptake in whole plants. A major difference in metabolism between the two species was the greater formation of the mono demethylated metabolite, B, [3-cyclohexyl-6-methylamino-l-methyl-l,3,5-triazine-2,4-dione] in P. melanocarpa which may also contribute to its greater tolerance. A loss of total ¹⁴Clabel from all plant parts with time may reflect cleavage of the ¹⁴C-ring-labelled herbicide.     

AN AUTORADIOGRAPHIC STUDY OF THE DISTRIBUTION OF 14C LABELLED ASSIMILATES AT DIFFERENT STAGES OF DEVELOPMENT OF OXALIS LATIFOLIA H.B.K. AND O. PES-CAPRAE L.

Summary. An autoradiographic study of the distribution of ¹⁴C-labelled assimilates, derived from ¹⁴CO₂ fed to the aerial parts, was made at ten different developmental stages of Oxalis latifolia H.B.K. and Oxalis pes-caprae L. Changing patterns of distribution of labelled assimilates to the underground parts of both species were revealed. These patterns are discussed in the context of the timing of control by defoliation and by foliageapplied herbicides.
Etude autoradiographique de la distribution des métabolites marqués an ¹⁴C à différents stades de développement de l'Oxalis latifolia H.B.K. et de l' O. pes-caprae L.     

PRELIMINARY STUDIES ON THE TRANSLOCATION OF 14C-LABELLED HERBICIDES IN BRACKEN (PTERIDIUM AQUILINUM)

Summary. The translocation of ¹⁴C-labelled herbieides in field bracken has been sludied in some preliminary experiments by means of autoradiography. A detailed account is given of the methods employed. It is shown that when 2,4-D is applied to fronds at different stages of development movement of the tracer into the rhizome is considerably greater from parts of the frond which are still immature. Trasnslocation within the frond is predominantly basipetal at all stages of development; within the rhizome the direction of movement appears to be determined primarily by the nature of the vascular connections with the treated pinna.
In a comparison between the translocation of 2,4-D, 4-CPA and dalapon no difference was apparent after 24 hours, but when the treatment period was extended to 96 hours there was evidence that 4-CPA bad been translocated in a considerably greater amount than either of the other two herbicides.
Rechrches iréliminaires sur la migration des herbieides marqués am ¹⁴ C dans la fougrère algle (Pteridium aquilinum)     

DEGRADATION OF FLUORODIFEN-1'-14C BY PEANUT SEEDLING ROOTS

Summary. Degradation of p -nitrophenyl-α,α,α:-trifluoro-2-nitro- p -tolyl ether (fluorodifen) labelled with ¹⁴C in the 1 position of the p -nitrophenyl ring (1'-¹⁴C) proceeded rapidly in peanut ( Arachis hypogaea L. cv. Starr) seedling roots. All degradation products were present after only 2 h.
The major degradation products for fluorodifen-1'-¹⁴C were the water-soluble compounds p -nitrophenol and Unknown I, a polar compound or complex which remained on the origin during thin-layer chromatography. Minor products included p -nitrophenyl-α,α,α-trifluoro-2-amino- p -tolyl ether, p -aminophenyl-α,α,α-trifluoro-2-nitro- p -tolyl ether and traces of p -aminophenol. No p -aminophenyl-α,α,α-trinuoro-2-amino- p -tolyl ether was detected. The p -aminophenol previously reported [ PL Physiol., Lancaster , 44,1397-1401 (1969)] was not p -aminophenol, but primarily Unknown I with a possible trace of p -aminophenol.
Fluorodifen continued to be absorbed throughout the 72-h treatment period.