Effects of temperature and concentration of the accelerators ethoxylated alcohols,diethyl suberate and tributyl phosphate on the mobility of [14C]2,4‐dichlorophenoxy butyric acid in plant cuticles

Intrinsic activities of monodisperse ethoxylated dodecanols (MEDs), diethyl suberate (DESU) and tributyl phosphate (TBP) were investigated using Stephanotis floribunda leaf cuticular membranes (CMs) and [¹⁴C]2,4‐dichlorophenoxy butyric acid (2,4‐DB) as a model solute. When sorbed in cuticular membranes, MEDs, DESU and TBP increase solute mobility and are called accelerators for this reason. With MEDs, dose‐effect curves (log mobility vs accelerator concentration) were linear but, with DESU and TBP, curves convex to the x axes were obtained that approached a maximum at 90 and 150 g kg⁻¹, respectively. Accelerators increased the mobility of 2,4‐DB in the CMs by 9‐ to 48‐fold, and effects were larger at lower temperatures (range 15–30 °C). Activation energy for diffusion of 2,4‐DB was 105 kJ mol⁻¹, decreasing with increasing accelerator concentrations to 26 kJ mol⁻¹ with DESU at 90 g kg⁻¹ and 64 kJ mol⁻¹ with TBP at 150 g kg⁻¹. Thus, the intrinsic activity of DESU was much higher than that of TBP, which implies that, for a given effect, less DESU than TBP would be needed. MEDs were also very effective accelerators, lowering activation energies to 36 kJ mol⁻¹. Data are discussed in relation to increasing rates of foliar penetration of active ingredients at low temperatures. © 2001 Society of Chemical Industry     

Effect of some ethoxylated alkylphenols and ethoxylated alcohols on the transfer of [14C] chlorotoluron across isolated plant cuticles

The effect of several ethoxylated octylphenols (OP), nonylphenols (NP) and alcohols (AA) on the penetration of [¹⁴C]chlorotoluron through isolated box-tree (Buxus sempervirens L.) leaf cuticles was investigated. The herbicide solution was deposited as droplets onto cuticle discs maintained on agar blocks acting as receivers. The effects on chlorotoluron transfer across the cuticles depended on the degree of ethoxylation of the surfactant. For each series, the chlorotoluron transfer was considerably increased by surfactants with low ethylene oxide (EO) content (3 to 6 EO). This effect appeared 24 h after droplet application, then increased with time. It decreased with further increase in the ethoxylation number, and surfactants with a long ethylene oxide chain (OP16, NP20, NP40 and AA20) had no effect. Surfactant concentration (OP5) had a large influence on chlorotoluron transfer; penetration increased sevenfold when OP5 concentration was raised from 0.01 to 10 g l^?1. Diffusion of the two tritiated octylphenols, [3H]OP5 and [3H]OP16, was measured simultaneously during chlorotoluron transfer. The diffusion rate of the two surfactants across the cuticles was similar, but a higher amount of OP5 was retained within the cuticle during transfer. Study of the effect of surfactants on the cuticular waxes using differential scanning calorimetry showed that wax begins to melt at a lower temperature in the presence of the nonylphenols NP9 and NP4. Fusion enthalpy was close to -30 J g^?1. Effet de quelques alkylphénols et alcools éthoxylés sur la pénétration du [¹⁴C]chlortoluron à travers des cuticules végétales isolées Nous avons testé l'effet de plusieurs octylphénols (OP), nonylphénols (NP) et alcools éthoxylés (AA) sur la pénétration du [¹⁴C]chlortoluron à travers des cuticules isolées de feuilles de buis. L'herbicide en solution était déposé sous forme de gouttelettes sur des disques de cuticules plaées sur agar. Les effets observés dépendaient du degré d'ethoxylation du surfactant. Pour chaque série, le transfert du chlortoluron à travers les cuticules était considérablement accru avec les surfactants faiblement éthoxylés (3 à 6 oxydes d'éthylène). Cet effet apparaissait 24 h après l'application des gouttelettes puis augmentait avec le temps. Il diminuait avec l'accroissement du nombre d'éthoxylation et aucun effet n'était observé avec les surfactants à longue chaine d'oxydes d'éthylène (OP16, NP20, NP40 et AA20). La concentration en surfactant (OP5) avait une grande influence sur le transfert du chlortoluron dans l'agar, il augmentait sept fois entre 0.01 et 10 g l^?1. La diffusion des deux octylphénols (³H-OP5 et ³H-OP16) a été mesurée simultanément durant le transfert du chlortoluron. La vitesse de diffusion des deux surfactants à travers les cuticules était comparable, mais une quantité plus élevée d'OP5 était retenue dans les cuticules durant le transfert. L'étude par analyse calorimètrique à balayage de l'effet des surfactants sur les cires cuticulaires a montré que la fusion des cires commence à plus faible température en présence des nonylphénols NP9 et NP4. L'enthalpie de fusion était en général voisine de -30 J g^?1. Wirkung einiger ethoxylierter Alkylphenole und Alkohole auf den Transfer von [¹⁴C]Chlortoluron durch die Pflanzen-Cuticula Die Wirkung verschiedener ethoxylierter Octylphenole (OP), Nonylphenole (NP) und Alkohole (AA) auf die Penetration von [¹⁴C]Chlortoluron durch die isolierte Blatt-Cuticula von Buxbaum (Buxus sempervirens L.) wurde untersucht. Die Herbizidlösung wurde als Tröpfchen auf Cuticula-Scheiben, die auf Agarblöcken als Empfänger ausgelegt worden waren, ausgebracht. Die Wirkung auf den Chlortoluron-Transfer durch die Cuticula hing von der Ethoxylierung des Zusatzstoffes ab. In allen Serien wurde der Transfer durch Zusatzstoffe mit niedrigem Gehalt an Ethyloxiden (EO) erheblich gesteigert (3 bis 6 EO). Diese Wirkung trat 24 h nach der Applikation der Tröpfchen ein und nahm dann mit der Zeit zu. Mit dem Anstieg der Ethoxylierungszahl nahm die Wirkung ab, und Zusatzstoffe mit einer langen Ethylenoxidkette (OP16, NP20, NP40 und AA20) waren wirkungslos. Die Konzentration des OP5-Zusatzstoffes hatte großen Einfluß auf den Chlortolurontransfer; die Penetration war versiebenfacht, wenn die OP5-Konzentration von 0,01 auf 10 g l^?1 angehoben wurde. Die Diffusion der Octylphenole [³H]OP5 und [³H]OP16 wurde während des Chlortolurontransfers gemessen; die Diffusionsrate war ähnlich, aber von OP5 wurde ein größerer Anteil in der Cuticula zuückgehalten. Die Wirkung der Zusatzstoffe auf das Cuticularwachs wurde calorimetrisch untersucht, und es zeigte sich, daß das Wachs in Gegenwart der Nonylphenole NP9 und NP4 bei niedriger Temperatur zu schmelzen beginnt. Die Fusionsenthalpie lag bei -30 J g^?1     

Characterizing pesticide and surfactant penetration with isolated plant cuticles

A survey is presented of the use of isolated leaf and fruit cuticles in studying foliar penetration. Isolated cuticles, which represent the prime barrier to penetration, provide a physical system with which transport studies can be conducted under well-defined and highly controlled conditions while avoiding the physiological effects of biologically active compounds on the system. Most studies with isolated cuticles have focused on sorption, desorption and infinite-dose cuticular transport of compounds in aqueous systems. Partition coefficients can be calculated for pesticides from sorption data, thereby yielding information on the solubility of the compounds in the cuticle. Permeance and diffusion coefficients can be calculated from cuticular transport studies. These transport parameters provide for a better understanding of the mechanisms of cuticular penetration. Further, they are useful in comparing both the penetration characteristics of selected compounds and permeability of cuticles. Transport systems, using isolated cuticles, may be used to quantify the effects of spray additives on pesticide penetration. A finite-dose system is described that may be useful in studying spray droplet/deposit interactions with the cuticle and, concurrently, following transcuticular penetration from droplets/deposits on the surface. These systems may prove useful in optimizing spray formulations and spray parameters, leading to more efficient pesticide development and application.     

Effects of surfactants on water permeability of isolated plant cuticles and on the composition of their cuticular waxes

Treating the outer surfaces of isolated cuticles of Seville orange (Citrus aurantium L.) and pear (Pyrus communis L. cv. Bartlett) leaves with a number of nonionic (polyoxyethylene) surfactants increased their permeability to water by factors ranging from 4.1 to 14.7 and from 7.2 to 152.4, respectively. However, sodium dodecylsulphate, an anionic surfactant, had little effect on water permeability. In both species the major aliphatic constituents were n-alkanes, 1-alkanols and n-alkyl esters. None of the surfactant treatments altered the amounts or composition of waxes in the cuticles used for transport measurements. The reasons for the apparent absence of solubilization or dissolution of cuticular waxes by nonionic surfactants are discussed and a hypothesis is presented for the mechanism by which activator adjuvants may increase the permeability of plant cuticles.     

Penetration of glyphosate and diuron into and through isolated plant cuticles

Penetration of ¹⁴C-glyphosate and ¹⁴C-diuron through plant cuticles was investigated using cuticles isolated from leaves of the box-tree (Buxus sempervirens) and rubber plant (Ficus elastica) and tomato (Lycopersicon esculentum) and pepper (Capsicum annuum) fruits. Herbicides were deposited in droplets on to cuticle discs maintained on agar under low or high humidity. The transfer into agar of each herbicide varied between plant species and was generally higher under higher humidity. A pronounced humidity effect was observed for glyphosate transfer through tomato fruit cuticles, reaching 94% transfer for this species but only 1–6% for the other three species. Diuron was well sorbed by cuticles. Its transfer into agar was greater through fruit (76–98%) than through leaf cuticles (2–30%). Kinetic measurements revealed that most penetration into agar occurred after the end of droplet evaporation for glyphosate, but during and after evaporation for diuron. Penetration of diuron through isolated tomato and pepper cuticles was lower from the inner surface than from the outer surface, but the difference between the two directions of penetration was not significant for glyphosate. Penetration of glyphosate through tomato cuticles decreased as cuticle thickness and wax content increased. No similar correlation was observed for diuron. Pénétration du glyphosate et du diuron dans et à travers des cuticules isolées de plantes La pénétration du ¹⁴C-glyphosate et du ¹⁴C-diuron à travers la cuticule de plantes a étéétudiée a l'aide de cuticules isolées de feuilles (buis, ficus) et de fruits (tomate, poivron). Les herbicides ont été déposés sous forme de gouttelettes sur des disques de cuticules placés sur des blocs d'agar, à faible et forte humidité. Le transfert dans l'agar des deux herbicides varie avec l'espèce végétale et est généralement plus élevé en présence d'une forte humidité. Un effet particulièrement prononcé de l'humidité est observé pour le transfert du glyphosate à travers les cuticules de tomate, la pénétration dans 1'agar atteint 94% pour cette espèce et seulement 1 à 6% pour les trois autres espèces. Le diuron est bien retenu par les cuticules. Son transfert dans 1'agar est plus élevé pour les cuticules de fruit (76–98%) qu'avec les cuticules de feuilles (2–30%). Les études cinétiques montrent que la pénétration dans 1'agar n'intervient qu'après 1'évaporation de la gouttelette pour le glyphosate alors qu'elle se produit durant et après 1'évaporation de la gouttelette pour le diuron. La pénétration du diuron à travers les cuticules isolées de poivron et de tomate est plus faible dans le sens surface interne-surface externe que dans le sens opposé, la différence entre les deux directions de pénétration n'est pas significative pour le glyphosate. La pénétration du glyphosate à travers les cuticules de tomate diminue avec l'augmentation de l'épaisseur ou de la teneur en cires des cuticules. II n'y a pas de corrélation semblable avec le diuron. Penetration von Glyphosat und Diuron in and durch isolierte Pflanzen-Cuticula Die Penetration von ¹⁴C-Glyphosat und ^l4C-Diuron durch die Pflanzen-Cuticula wurde an isolierten Cuticulae von Blättern von Buchsbaum (Buxus sempervirens) und Gummibaum (Ficus elastica) und von Früchten von Tomate (Lycopersicon esculentum) und Paprika (Capsicum annuum) untersucht. Die Herbizide wurden als Tröpfchen auf Cuticula-Scheiben, die bei niedriger oder hoher Luftfeuchtigkeit auf Agar-Agar ausgelegt waren, ausgebracht. Der Übergang der Herbizide in den Agar-Agar war je nach Pflanzenart verschieden, bei hoher Feuchte allgemein stärker. Dieser Effekt war für Glyphosat bei Tomaten-Cuticula besonders deutlich, indem hier 94%übergingen, bei den anderen 3 Arten aber nur l bis 6%. Diuron wurde von den Cuticulae gut aufgenommen, sein Übergang war bei Frucht-Cuticulae stärker (76 bis 98%) als bei Blatt-Cuticulae (2 bis 30%). Messungen der Kinetik ergaben, daß bei Glyphosat die meiste Penetration nach dem Austrocknen der Tröpfchen, bei Diuron aber während und nach dem Austrocknen ablief. Der Ubergang von Diuron durch Tomaten- und Paprika-Cuticula war von den Innenflächen her stärker als von den Außenflächen, was sich für Glyphosat nicht signifikant zeigte. Die Penetration von Glyphosat durch Tomaten-Cuticula nahm mit zunehmender Dicke und Wachsgehalt ab; für Diuron konnte keine solche Korrelation beobachtet werden.     

Cuticular penetration of 2,4-D as affected by interaction between a diethylene glycol monooleate surfactant and apple leaf cuticles

Impacts of pH and sorption-desorption of ‘Pegosperse’ 100-O (PEG. 100-O; diethylene glycol monooleate, containing 15% diester) surfactant by apple (Malus pumila M.) leaf cuticles on surfactant-enhanced cuticular penetration of 2,4-D [(2,4-dichlorophenoxy)acetic acid] were studied. Glass cylinders were affixed to enzymatically isolated adaxial apple leaf cuticles after the cuticle segments had been soaked in 10 ml liter^?1 PEG 100-O solution and washed for 20 and 120 min, respectively. Quantities of [¹⁴C]2,4-D in the glass-cuticle chambers passing through the cuticles at pH values from 1 to 6 5 were determined. PEG 100-O significantly increased cuticular penetration of dissociated 2,4-D at pH 4–5; the surfactant had no effect on penetration of undissociated 2,4-D at pH 10. Surfactant-enhanced penetration of 2,4-D occurred only when the surfactant was in the cuticles, while the process of surfactant sorption-desorption alone had no effect on penetration. These results support a ‘hydrophilic channel’ hypothesis, i.e. that surfactants may create hydrophilic channels or increase the area of the channels in the cuticle and, consequently, enhance the passing of polar molecules like dissociated 2,4-D through the cuticle.     

The influence of plant age on the movement of 2,4-D and assimilates in wheat

A quantitative study of the movement of 2,4-D and assimilates was made using radiocarbon-labelled materials. At the two-three leaf stage of wheat (cv Koga II) 2,4-D moved more slowly than assimilates, but the patterns of movement were very similar. At the five-six leaf stage of the cereal there were differences between 2,4-D and assimilates in the patterns of distribution from leaf 1 and from a leaf on a tiller. In both cases relatively less 2,4-D moved into roots than would have been predicted from knowledge of assimilate movement. Total amounts of 2,4-D reaching the roots did not differ significantly between growth stages but due to root growth, the concentration of radio-activity in the roots fell.     

Translocation of 2,4-D, asulam and amitrole in water hyacinth

In glasshouse experiments foliar application or ¹⁴C-labelled herbicides to water hyacinth plants at the 4-leaf stage indicated that amilroie transport from the treated leaf blade was faster and greater than 2.4-D. but a little less than asulam. From the treated leaf 14·2, 25·9. 39·7. 44·5 and 51·8% of the recovered ¹⁴CNamitrole was translocated at intervals of 6 h. and 1. 3. 6 and 12 day., respectively. Both xylem and phloem transport of asulam and amitrole was evident, whereas 2.4-D moved only from ‘source to sink’. Movement of the herbicides from the mother to the connected daughter plant or vice versa was dependent upon the size of the latter. Maximum transport of these herbicides in either direction took place at the 2-leaf stage of daughter plants. With any increase or decrease in the number of leaves on daughter plants, the transport of herbicides was reduced. As an exception, daughter plant to mother plant movement of amilroie was maximum at the 1-leaf stage. After extraction, fractionation and TLC separation of foliage applied ¹⁴C-2.4-D 76–4 and 72·1% of the radioactivity was detected in the chloroform phase of the leaf extract at 3 and 6 day intervals, respectively. In another pot culture experiment, it was observed that after spraying the mother plants with 2.4-D-amine at 0–75 kg/ha the connected daughter plants at 1 to 4-leaf stages werckilled if the culture solution was contaminated while spraying, or by dying leaves. When contamination was totally avoided, the connected but unsprayed daughter plants at 3 to 4-feaf stages survived.     

Effects of bifenox and oxadiazon on isolated chloroplasts,plant mitochondria and leaf pieces

The effects of bifenox (methyl 5-(2,4-dichlorophenoxy)-2-nitrobenzoate) and oxadiazon (5-tert-butyl-3-(2,4-dichloro-5-isopropoxyphenyl)-1,3,4-oxadiazol-2(3H)-one on photosynthetic activity were investigated in isolated chloroplasts, and on respiratory activity in isolated mitochondria. The global effects of these chemicals were also investigated on cucumber cotyledon pieces. It was found that, in vitro, bifenox and oxadiazon acted on cotyledon pieces as typical diphenyl ether herbicides, causing complete pigment bleaching, even at low concentrations. In addition, bifenox and oxadiazon were shown to inhibit the photosynthesis process at the chloroplast level. At concentrations of up to 40-50 μM, oxadiazon and bifenox were observed to inhibit fully the light-dependent oxygen evolution of spinach class A chloroplasts, oxadiazon acting preferentially on electron transfer at the PS II level whereas bifenox acted on the photophosphorylation process. Comparison of the amounts of herbicide needed to inhibit photosynthesis and to cause bleaching of cucumber pieces leads to the conclusion that photosynthesis inhibition by bifenox and oxadiazon is only a secondary effect.     

Finite dose diffusion studies: III. Effects of temperature, humidity and deposit manipulation on NAA penetration through isolated tomato fruit cuticles

Effects of temperature, humidity, rewetting and removal of deposits on penetration of NAA [2-(1-naphthyl)acetic acid] through isolated tomato (Lycopersicon esculentum Mill) fruit cuticles were studied using a finite dose diffusion system. In this system, an aqueous 5-microliter droplet (0.1 mM NAA in 20 mM citric acid buffer) is applied to the outer surface of a cuticle, which is mounted in a glass diffusion half-cell. The cell wall surface is in contact with a receiver solution (20 mM citrate). Penetration is monitored by repeated sampling of the receiver solution. Droplets appeared dry on visual inspection within 1 h of application, but significant NAA penetration continued after droplet drying. Maximum rates of NAA penetration increased exponentially as temperature was increased (from 5 degrees to 35 degrees C), the energy of activation averaging 153 (+/- 11.6)kJ mol-1. At 35 degrees C, penetration reached a plateau within 10 h of application (at 91.1 (+/- 1.0)% of dose applied) while at 5 degrees C penetration after 800 h reached only 30.2 (+/- 7.5)%. Increasing relative humidity from 20 to 80% increased maximum rates [from 1.0 (+/- 0.21) to 2.7 (+/- 0.80)% h-1] and penetration at 120 h after application [from 36.8 (+/- 2.1) to 64.3 (+/- 3.7)%]. Rewetting deposits at 120, 240 and 360 h after application resulted in increased NAA penetration. However, amounts and rates of NAA penetration progressively decreased with each subsequent rewetting. Removal of deposits by cellulose acetate stripping at various times after droplet application resulted in a rapid decrease in NAA penetration. NAA penetration following deposit removal was always less than 6.1% of the amount of NAA applied and averaged 0.5 (+/- 0.2)% when deposits were removed immediately after droplet drying.     

Effect of low temperatures on 2,4-D behaviour in maize plants

The foliar surface of 4-leaf maize plants was found to be poorly wettable and retained 106 μl g^?1 dry matter when sprayed with a U46D (2,4-D formulation) blank. The third leaf retained 141 μl g^?1. A 7-day cold spell (17/9°C) increased retention per unit dry matter by 53% (135% on the third leaf). Cold stress lowered epicuticular wax quantity by 29% on the third leaf. Contact angles of formulated 2,4-D lay between 115 and 125° and were not significantly affected by cold stress. 2,4-D rapidly entered into maize third leaf (66% in 24 h) but migration from it was less than 1.5%. 2,4-D was readily degraded in maize (80% in 72 h). The most abundant metabolite was probably an ester conjugate; little of the hydroxy derivatives were found. Cold stress reduced 2,4-D degradation, and 72 h after treatment the amount of undegraded 2,4-D was 78% higher in cold-stressed maize plants. It was concluded that 2,4-D selectivity in maize results from low spray retention per unit dry matter and active degradation of penetrated herbicide. Cold stress affects both factors.     

Spray application factors and plant growth regulator performance: II. Foliar uptake of gibberellic acid and 2,4-D

Effects of droplet size and carrier volume on foliar uptake and translocation of gibberellic acid (GA₃) and 2,4-D were investigated. Simulated spray droplets were applied to primary leaves of 10-day-old Phaseolus vulgaris (cv Nerina) in droplet sizes and carrier volumes ranging from 0.5 to 10 μl and 10 to 200 μl per leaf, respectively. Doses of GA₃ (2 μg per leaf) and 2,4-D (100 μg per leaf) were held constant. Total uptake of GA₃ approached a penetration equilibrium within 24 h after application, but uptake of 2,4-D continued to increase. Decreasing droplet size and/or increasing carrier volume increased GA₃ and 2,4-D uptake. Translocation to stem and roots was positively related to total uptake. A positive linear relationship between the logarithm of the total droplet/leaf surface interface area and 2,4-D uptake or translocation was found, but for GA₃ this relationship was quadratic. Potential mechanisms of the effects of spray application factors on foliar uptake are discussed. © 1999 Society of Chemical Industry     

The determination of residues of 2,4-D in post-emergence-treated triticale

A gas chromatographic method, using electrolytic conductivity detection, is presented for the determination of 2,4-0 as its methyl ester in triticale (X Triticosecale Wittmack). The method was used to monitor the dissipation of 2,4-0 residues in triticale over a growing season at two sites following post-emergence application of the dimethylamine salt of 2,4-D at 0.56 kkg ha^?1. Initial residues, in the order of30 mg kg^?1. on the day afer application (3- to 4-leaf stage of the crop), decreased to non-detectable levels in the mature straw and seed. Recoveries of 2,4-D were greater than 90% fiom green tissue fortified at 0.1 mg k^?1., and in the order of 75% from seed fortified at 0.05 mg kg^?1.     

2,4-滴丁酯土壤处理对大豆产量的影响

以黑龙江不同积温带的3个大豆主栽品种‘东农52’、‘合丰55’、‘黑河48’为材料,运用盆栽试验方法,在大豆播后苗前施用不同剂量的2,4-滴丁酯进行土壤处理,探讨了2,4-滴丁酯对不同大豆品种的产量及产量构成因素的影响。结果表明：2,4-滴丁酯对供试3个大豆品种的百粒重均无影响;2,4-滴丁酯造成大豆减产的处理,大豆单株粒数必然减少,而单株荚数、有效荚数不一定减少,造成大豆减产的主要原因是大豆单株粒数减少。可见,施用2,4-滴丁酯是否造成大豆减产可通过调查大豆单株粒数进行评判;供试3个大豆品种对2,4-滴丁酯的敏感性不同,2,4-滴丁酯施药量达1 080 g/hm2时引起‘黑河48’减产,达1 620 g/hm2时引起‘东农52’减产,达2 160 g/hm2时才引起‘合丰55’减产。供试大豆品种对2,4-滴丁酯的敏感性顺序为：‘黑河48’>‘东农52’>‘合丰55’。     

2,4-滴异辛酯的水解及光解特性

为明确2,4-滴异辛酯的环境行为规律,采用室内模拟试验方法,研究了2,4-滴异辛酯在不同温度、pH值、水体及初始浓度下的水解特性及其在不同pH值、水体、光源和初始浓度下的光解特性。结果表明:中性 (pH = 7) 条件下,初始质量浓度为5 mg/L的2,4-滴异辛酯在15、25 和35 ℃ 下的水解半衰期分别为346.6、231.0和173.3 h;25 ℃下,5 mg/L的2,4-滴异辛酯在pH值分别为4、7 和9 的缓冲溶液中的水解半衰期分别为77.0、231.0 和138.6 h;2,4-滴异辛酯在稻田水、自来水和河水中的水解速率高于其在蒸馏水中的水解速率,4 种条件下的半衰期分别为23.1、25.7、40.8 和63.0 h;初始质量浓度分别为1、3和5 mg/L的2,4-滴异辛酯在pH值为7的缓冲溶液中的水解半衰期分别为231.0、173.3和138.6 h。300 W汞灯照射下,2,4-滴异辛酯在酸性条件下的光解速率大于其在中性和碱性条件下,半衰期分别为49.5、77.0 和138.6 h;2,4-滴异辛酯在河水和稻田水中的光解速率高于其在自来水和蒸馏水中的光解速率,4 种条件下的半衰期分别为6.7、7.6、43.3 和46.2 h;2,4-滴异辛酯在不同光源下的光解速率依次为500 W汞灯 > 300 W汞灯 > 500 W氙灯;初始质量浓度分别为1、3和5 mg/L的2,4-滴异辛酯在pH值为7的缓冲溶液中的光解半衰期分别为63.0、43.3和40.8 h。2,4-滴异辛酯水解及光解的主要产物是2,4-滴,其降解机制主要是酯水解反应。研究结果可为2,4-滴异辛酯的合理使用及其环境风险评估提供参考。     

Physiological actions of dinoterb,a phenol derivative: 2. Effects on isolated plant mitochondria and chloroplasts

Dinoterb, a contact herbicide, affects respiration and photosynthesis of mitochondria and chloroplasts. On mitochondria, at low concentrations, it acts as an uncoupler of oxidative phosphorylation; at higher concentrations, it inhibits the electron transport chains, probably before cytochrome c. On chloroplasts, dinoterb has a stimulatory effect on oxygen uptake in the reduced dichlorophenol-indophenol→methyl viologen couple; however, it is also an inhibitor of the Hill reaction and its site of inhibition is located before plastoquinone, near photosystem II.     

The effect of repeated applications of 2,4-D and MCPA on their breakdown in soil

The effect of repeated applications of 2,4-D and MCPA in a long-term field experiment on their subsequent degradation was investigated. The herbicides had been applied annually since 1954, Comparisons were made with plots treated once and then retreated the following year. Repealed applications of the two herbicides resulted in a reduction in degradation lime from 10 weeks for 2,4-D and 20 weeks for MCPA after one application to 4 and 7 weeks respectively after 19 years of annual application. In spite of an increased capability of the soil microflora lo degrade 2,4-D and MCPA 9 months after a previous treatment. no change in numbers of organisms capable of utilizing the substances as carbon sources were found in treated plots as compared with the control. It is obvious that there is a cross adaptation between 2,4-D and MCPA. It seems most likely that two different ‘enrichment’ been induced, each capable of decomposing both herbicides, but with different efficiencies. Effet d'applications répétée de 2,4-D et de MCPA sur leur degradation dans le sol L'effet d'applications répétée de 2.4-D et de MCPA sur leur degradation uléerieure a étéétudié dans une expérience au champ de longue durée. Les herbicides ont été appliqués chaque année depuis 1954. Des comparaisons ont été effectuées avec des parcelles traiées une fois et traitées à nouveau l'année suivante. Les applications répétées des deux herbicides ont provoqué une réduction du temps de dégradation qui est passé de 10 semaines pour le 2,4-D et 20 semaines pour le MCPA après une seule application, à 4 et 7 semaines respectivement, après 19 années d'applications annuelles. En dépit d'une capacité accrue de la microflore du sol à dégrader le 2.4-D et le MCPA, neuf mois après un traitement préalable, aucun changement n'a été constaté dans le nombre des organismes capables d'utiliser les produits comme sources de carbone dans les parcelles traitées, par rapport au témoin. II est évident qu'il y a une adaptation croisée entre le 2,4-D et le MCPA. II apparait très probable que deux ‘enrichissements’ de Hores ont été induits, chacun d'eux étant capable de décomposer les deux herbicides mais avec des efficacités différentes. Die Wirkung wiederholter Behandlungen von 2.4- D und MCPA auf ihren Abbau im Boden Die Wirkung wiederholter Anwendungen von 2,4-D und MCPA auf ihren Abbau wurden in einem Freiland-Versuch untersucht. Die Herbizide wurden jährlich, sell 1954 ange-wendet. Es wurden Vergleiche mil Parzellen angcstellt, die zum erstenmal und im folgenden Jahr nochrnaK bchandelt worden waren. Die widerholien Behandlungen mit den beiden Herbiziden bewirkte elne Verringerung der Ab-bauzeit von 10 Wochen fur 2,4-D und 20 Wochen fiir MCPA nach einer Behandlung, auf 4 bzw. 7 Wochen nach 19 Jahren jahrlicher Anwendung. Trotz der erhohten Ffihigkeit der Bodenmikroflora 2,4-D und MCPA neun Monate nach einer vorhergehenden Behandlung abzubauen, war die Zahl der Organismen, die diese Herbizide als Kohlensloffquelle verwerten konnen, in den behandelten und unbehandelten Parzellen gleich gross. Zwischen 2.4-D und MCPA existiert ofVensichtlich elne Kreuz-Adaplalion. Sehr wahrscheinlich wurden zwei versehiedene ‘enrichment’-Floren induziert, von der jede in der Lage ist beide Herbizide, aber mit unterschiedlicher Effizienz, Hbzubauen.