Alachlor influence on sorghum growth and gibberellin precursor synthesis

Growth (14 days) of sorghum (Sorghum bicolor L. cv G522 DR) from seed planted in sand into which alachlor [2-chloro-2′,6′-diethyl-N-(methoxymethyl)acetanilide] was uniformly incorporated (0, 0.07, 0.14, 0.28, 0.56, 1.12, 2.24, or 4.48 kg/ha) was reduced by 0.14 kg/ha and severely inhibited (88%) by 0.56 kg/ha while cellular water cotent was not greatly influenced by 0.56 kg/ha. When added into the nutrient solution bathing the roots of 96-hr sorghum seedlings, alachlor (0, 0.0156, 0.0312, 0.0625, 0.125, 0.25, 0.5, 1, 2, 4, 8, 16, 32, 64, or 128 ppmw) was not lethal to 14-day-old sorghum at rates up to 32 ppmw (92% survival); however, shoot and root lengths were reduced 43 and 58%, respectively. Alachlor inhibition of sorghum growth appears to be closely associated with inhibition of cell enlargement; the coleoptile is the most susceptible stage of sorghum growth to alachlor. This situation closely resembles growth where gibberellic acid (GA) synthesis is inhibited. [2-¹⁴C]Mevalonic acid ([2-¹⁴C]MVA) incorporation into terpenoid GA precursors was evaluated using a cell-free enzyme system from etiolated sorghum coleoptiles. Alachlor did not inhibit total ¹⁴C incorporation but incorporation of ¹⁴C into kaurenol and sterols was decreased ca 80 and 75%, respectively, by 10^?6M alachlor. Analyses for [¹⁴C]geranylgeraniol (GG), [¹⁴C]farnesol, and [¹⁴C]geraniol contents showed accumulation of [¹⁴C]farnesol and [¹⁴C]GG, and decreased [¹⁴C]geraniol. When seeds to which CGA-43089 [α-(cyanomethoximino)-benzacetonitrile] was applied 8 weeks prior to planting were substituted for untreated seeds, incorporation of [2-¹⁴C]MVA into [¹⁴C]kaurenol was increased by alachlor while [¹⁴C]GG and [¹⁴C]farnesol accumulated and [¹⁴C]geraniol was absent at 10^?6M alachlor. Additionally, sterol content increased in “safened” systems but was still decreased by alachlor. These data demonstrate multiple sites of alachlor activity in the GA and terpenoid biosynthetic pathway.     

Diallate inhibition of gibberellin biosynthesis in sorghum coleoptiles

Diallate [S-(2,3-dichloroallyl)diisopropylthiocarbamate] incorporated into sand significantly inhibited sorghum (Sorghum bicolor (L.) Moench cv Funks G 522DR) growth of 14-day-old seed lings. Inhibition was competitively reversed by exogenous giberellic acid (GA₃) (0.1 and 10 ppmw). Diallate inhibited gibberellin (GA) precursor biosynthesis in a cell-free enzyme preparation from unruptured, etiolated sorghum coleoptiles. Diallate (10 μM) inhibited kaurene oxidation 40% with a 2.7 × increase in kauren-ol and a 50% decrease in kaurenoic acid. The GA biosynthesis inhibition correlates with symptom phenology and field use application concentrations. Geranylgeranyl pyrophosphate accumulated 5 × at 0.1 μM diallate concentrations but concomitant kaurene concentration decreases did not occur. At 10 μM diallate, kaurene synthetase was inhibited 33%.     

Effect of herbicide antidotes on glutathione content and glutathione S-transferase activity of sorghum shoots

The effects of the herbicide antidotes CGA-92194 (α-[(1,3-dioxolan-2-yl-methoxy)-imino]benzeneacetonitrile), flurazole [phenylmethyl 2-chloro-4-(trifluoromethyl)-5-thiazolecarboxylate], dichlormid (2,2-dichloro-N,N-di-2-propenylacetamide), and naphthalic anhydride (1H,3H-naphtho(1,8-cd)-pyran-1,3-dione) on nonprotein thiol content, glutathione content, and glutathione S-transferase (GST) activity in etiolated sorghum (Sorghum bicolor L.) Moench) shoots were examined. CGA-92194 and naphthalic anhydride had no effect on nonprotein thiol or reduced glutathione (GSH) content of sorghum shoots. In contrast, dichlormid and flurazole increased nonprotein thiol content of sorghum shoots by 24 and 48%, respectively. These increases were largely attributable to an increase in GSH. The antidotes increased GST activity less than twofold when using CDNB (1-chloro-2,4-dinitrobenzene) as a substrate. In contrast, when using metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] as a substrate, the increase in GST activity in response to antidote treatment was much greater: flurazole (30-fold), CGA-92194 (20-fold), naphthalic anhydride (17-fold), dichlormid (5-fold). The degree of protection from metolachlor injury conferred by a particular antidote was strongly correlated (R² = 0.95) with its ability to enhance GST activity, as evaluated with metolachlor as substrate. A comparison of GST activity in untreated and CGA-92194-treated seedlings, over a range of metolachlor concentrations (0.5–500 μM), indicated that the relative enhancement of enzyme activity by CGA-92194 was greater at lower metolachlor concentrations. The rate of nonenzymatic conjugation of metolachlor and GSH in vitro was much less (on a gram fresh weight equivalent basis) than the enzymatic rate. These results are consistent with the hypothesis that the above antidotes protect sorghum by enhancing GST activity which results in accelerated detoxification of metolachlor via GSH conjugation.     

Gibberellin influence on membrane disruption by thiocarbamate herbicides

Vernolate (0, 8, 16, 31, 62, 125.0, or 250.0 ppbw) incorporated into sand inhibited the growth of wheat (Triticum aestivum L. cv Holley) at 125.0 ppbw. These growth inhibition and morphological responses were virtually identical to wheat response to EPTC at 125 ppbw. ¹⁴C from vernolate (carbonyl labeled) (125.0 ppbw) was absorbed into wheat seedlings at approximately 1.8 μM on the presumption that the ¹⁴C present was [¹⁴C]vernolate. Since the response of wheat to the thiocarbamate herbicides resembles a gibberellic acid (GA) deficiency and cell enlargement requires the presence of functional plasmalemmas and tonoplasts, the question of membrane disruption by excessive concentrations of thiocarbamate herbicides and potential reversal thereof by GA₃ was studied by measuring the efflux of K⁺, Na⁺, and Mg²⁺. GA₃ (0.003 μM) stimulated lettuce leaf disc growth in diameter and fresh weight. This GA-stimulated increase in size and weight was reversed by 1 mM EPTC. Betacyanin efflux from beet leaf tonoplasts was increased by 1 mM EPTC and this efflux was not reversed by exogenous GA₃ (0.3 μM). This influence by supraoptimal EPTC concentrations was shown to be via membrane disruption, which obviated any possible GA influence by eliminating the functionality of the membranes requisite to the development of a GA response. It is concluded that viable mode-of-action studies must measure physiological responses consistent with the symptomology of herbicide responses normally observed with each herbicide at field concentrations.     

The role of waxes in the uptake of metolachlor into sorghum in relation to the protectant CGA 43089

The grass weed herbicide metolachlor (2-chloro-N-[2-ethyl-6-methylphenyl]-N-[2-methoxy-1-methylethyl]acetamide) which is especially effective against wild millets, inhibits the formation of epicuticular waxes on sorghum leaves. The metolachlor protectant CGA 43089 [α - (cyanomethoximino) - benzacetonitrile] prevents the depletion of the waxes on the leaves of metolachlor-treated sorghum plants, as demonstrated by scanning electron microscopy. This alteration of the plant surface polymers also changes their permeability to the herbicide. ¹⁴C-metolachlor uptake into isolated coleoptiles and first leaves of sorghum which had been pretreated with the herbicide was increased. Incubation with added protectant reduced the uptake of ¹⁴C-metolachlor. It is postulated that the modifications caused by metolachlor and its protectant to sorghum surface structures influence the action of the herbicide in two ways:

• 1 The selectivity observed against sorghum and millet grasses could occur because of an increased uptake of metolachlor through cuticles which are particularly sensitive to the structural changes caused by the herbicide, since the composition of the plant waxes is very species-specific.
• 2 The loss of cuticular integrity is prevented by the protectant CGA 43089, which greatly reduces penetration of metolachlor.

     

Effects of N, P and K on Striga asiatica (L.) Kuntze seed germination and infestation of sorghum

Sorghum (Sorghum bicolor (L.) Moench) plants were grown in pots with 12.5 and 50 mg applied N kg^?1 soil. With an increase of soil N, the Striga asiatica (L.) Kuntze infestation, as well as the sorghum shoot dry matter losses due to infestation, decreased. The relative differences in stimulant capacity to induce Striga seed germination among the four sorghum genotypes were not consistent over the 0 to 150 mg N 1^?1 range. The sorghum root exudate was considerably more active at 0 mg N 1^?1, than at 30 mg N 1^?1, and the stimulant produced at 150 mg N 1^?1 failed to induce Striga seed germination. Presence of N in the growth medium considerably reduced the effectiveness of the stimulating substance produced by sorghum roots, whereas K promoted stimulant activity only in the absence of N. The presence or absence of P in the growth medium did not affect Striga seed germinability, probably due to the inability of this element to interfere with the production or activity of the stimulating substance from the host plants. It can be concluded, therefore, that sorghum plants seem to produce active root exudate only in conditions of N deficiency.     

Metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide] inhibition of gibberellin precursor biosynthesis

[2-¹⁴C]Mevalonic acid incorporation into gibberellic acid precursors was measured in cell-free extracts from sorghum [Sorghum bicolor (L.) Moench var. G-522 DR] coleoptiles. ¹⁴C incorporation into ent-kaur-16-ene was inhibited ca. 90% by 10^?7 to 10^?4M metolachlor [2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-1-methylethyl)acetamide]. [¹⁴C]Geranylgeraniol (GG) content increased. [¹⁴C]Farnesol content was not altered and [¹⁴C]geraniol content decreased. Total ¹⁴C incorporation was decreased by metolachlor. In the safener [α-(cyanomethoximino)benacetonitrile]-treated sorghum seed coleoptile cell-free system, total ¹⁴C incorporation increased, [¹⁴C]kaurene and relative kaurence content increased 4× up to 10⁵M metolachlor, and [¹⁴C]farnesol, and [¹⁴C]GG contents increased while relative farnesol and relative GG contents were not influenced by metolachlor. Thus, the inhibition of kaurene synthesis by metolachlor was reversed by the safener. Since the biosynthetic processes are mevalonic acid → geraniol → farnesol → GG → copalylol → kaurene, these data corroborate a proposed gibberellic acid biosynthesis inhibition between GG and kaurene as well as a partial blockage between mevalonic acid and geraniol. Thus, a portion of metolachlor-induced growth inhibitions of sorghum could be explicable on the basis of gibberellic acid biosynthesis inhibitions.     

Increased metabolism of a pyrrolidine urea herbicide in corn by a herbicide antidote

Corn, cotton, and sorghum plants were injured by high rates of 5328 (cis-2,5-dimeihyl-1-pyrrolidinecarboxanilide) when it was applied to the soil surface al planting time. The injury was severe al 35·84 kg/ha (eight times recommended dosage) and in corn resulted in complete inhibition of adventitious root development and reduced shoot and primary and secondary root growth. Treatment of the seeds with 0·5% Protect (1,8-naphthalic anhydride) prior to planting dramatically decreased the injurious effect of 5328 on corn, sorghum, and cotton. Using ¹⁴C-5328 in corn, it was shown that Protect did not alter herbicide uptake. However, the rate of conversion of the herbicide molecule in corn tissue lo water soluble, nonherbicidal metabolites was markedly enhanced in plants grown from Protect-treated seeds.     

Metolachlor (2-chloro-N-[2-ethyl-6-methylphenyl]-N-[2-methoxy-l-methylethyl] acetamide) and the metolachlor safener CGA 43089 [α-(cyanomethoximino)-benzacetonitrile] in sorghum seedlings: Correlations between morphological effects and ethylene formation

Treatment of germinating sorghum [Sorghum bicolor (L.) Moench] seeds with the grass herbicide, metolachlor (2-chloro-N-[2-ethyl-6-methylphenyl]-N-[2-methoxy-1-methylethyl] acetamide), causes growth retardation, promoted by thickening of the first leaf and thus inhibition of unfolding of secondary leaves, and increased ethylene production. Sorghum seeds pretreated with the safener CGA 43089 [α-(cyanomethoximino)-benzacetonitrile] exhibit neither morphological deformations nor ethylene production upon metolachlor treatment. Aminoethoxyvinylglycine [l-2-amino-4-(2-aminoethoxy)-trans-3-butenoic acid], a specific inhibitor of ethylene formation in higher plants, decreases ethylene formation by metolachlor-treated sorghum seedlings; the observed deformations, however, remain unchanged. Sorghum control seedlings which grow against a covering plate build up ethylene concentrations as after herbicide treatment, but without induction of the morphological symptoms. These observations suggest that the plant hormone ethylene is a symptom and not the inducer of the morphological effects visible after metolachlor treatment of sorghum seedlings.     

Measuring cysteine biosynthesis activity from serine in extracts from sorghum, corn and grass weeds, and their metolachlor susceptibility

In vitro assay procedures for measuring the activity of cysteine biosynthesis from serine (CBS), which is a coupled reaction catalyzed by serine acetyltransferase and cysteine synthase, were developed using crude extracts from sorghum shoots. Cysteine biosynthesis from serine activity was dependent on acetyl‐CoA concentrations (up to 1.5 mmol L^?1), serine (at least up to 20 mmol L^?1) and sulfide (up to 0.25 mmol L^?1), respectively, and was proportional to the protein concentration in the reaction mixture below 0.4 mg mL^?1. The reaction rate was 6.6 nmol min^?1 per mg of protein during the first 5 min, but increased to 45.6 nmol min^?1 per mg of protein between 30 and 45 min after reaction initiation. Sorghum had the highest CBS total activity (222.4 nmol min^?1 per g of fresh weight), and large crabgrass had the lowest CBS total activity (4.7 nmol min^?1 per g of fresh weight) when CBS activity in shoots was extracted from sorghum, corn, johnsongrass, barnyardgrass, goosegrass, green foxtail and large crabgrass. Similar results were obtained for CBS specific activity (nmol min^?1 per mg of protein). There was no correlation between total CBS activity and susceptibility to metolachlor; however, when corn was excluded, a correlation of R² = 0.690 was found. Flurazole seed treatment (1.25 g per kg of seed) conferred metolachlor resistance by sorghum, and enhanced total CBS activity and non‐protein thiol content by 27 and 61%, respectively. The increase in thiol content presumably contributed to metolachlor tolerance in sorghum. From these results, the difference in CBS activity partially contributes to the selectivity to metolachlor among certain grass species, and to the safening action of flurazole by increasing thiol content.     

Comparative metabolism of atrazine and EPTC in proso millet (Panicum miliaceum L.) and corn

The purpose of this study was to examine the differential activities of proso millet (Panicum miliaceum L.) and corn (Zea mays L.) with respect to atrazine [2-chloro-4-(ethylamino)-6-(isopropylamino)-S-triazine] and EPTC (S-ethyldipropyl thiocarbamate) metabolism. GSH-S-transferase was isolated from proso millet shoots and roots. When assayed spectrophotometrically using CDNB (1-chloro 2,4-dinitrobenzene) as a substrate, the shoot enzyme had only 10% of the activity of corn shoot enzyme while the root enzyme had 33% the activity of corn root enzyme. However, when proso millet shoot GSH-S-transferase was assayed in vitro using ¹⁴C-ring-labeled atrazine, it degraded the atrazine to water-soluble products at the same rate as the corn shoot enzyme. Incubation of excised proso millet and corn roots with [¹⁴C]EPTC indicated that uptake of EPTC was similar in both plants. However, proso millet metabolized the EPTC to water-soluble products at only half the rate of corn. Glutathione levels of proso millet roots were 35.9 μg GSH/g fresh wt, compared with 65.4 μg GSH/g fresh wt for corn. However, a 2.5-day pretreatment with R-25788 (N,N-diallyl-2-2-dichloroacetamide) elevated proso millet GSH levels to 62.7 μg GSH/g fresh wt. R-25788 did not elevate the activity of proso millet GSH-S-transferase, in contrast to its effects on corn. We conclude that differences in response to atrazine and EPTC in proso millet and corn are a result of their differential metabolism.     

The influence of ammonium and nitrate nutrition of tomato plants on parasitism by the root-knot nematode

Tomato plants grown in sand-silica culture in 0.75-liter pots and 50-liter containers were fertilized with three ratios of NH₄ ⁺/N0₃ ^- percentages: 100/0, 50/50, and 0/100. The seedlings were inoculated with the root-knot nematode,Meloidogyne javanica, and 30 and 60 days after inoculation top and root fresh weights, nematode infection degree and sex ratio of the nematode populations were recorded, and N, P, K analyses of plant tops and roots were conducted. Nematode development was not influenced by the nutrient treatments but a reduced nematode population per mm of root, and a high percentage of males in the population were associated with the 100% ammonium treatment. Increased nitrate level in the medium enhanced fresh top and root weights in the pots and, especially, in the containers. High levels of N and K in the first month, and of N, P, K in the second month, accumulated in the inoculated roots, particularly in the nitrate-fertilized plants. The results support the theory of the existence of a metabolic sink in roots ofMeloidogyne-infected plants and suggest an increased tolerance to the root-knot nematode in plants receiving nitrate nutrition.     

黄腐酸对乙草胺生物活性及持效期的影响

采用玉米根长法或芽长法研究了黄腐酸对乙草胺的生物活性、持效期和除草效果的影响.结果显示:乙草胺浓度和玉米根芽生长呈明显负线性关系,乙草胺浓度与根芽的线性方程为Y1=0.098x1+9.449和Y2=0.079x2+22.255,相关系数R1=-0.9916、R2=-0.9809;黄腐酸能够提高乙草胺的生物活性和除草效果,并延长乙草胺的持效期,添加0.25%～4.00%黄腐酸,乙草胺抑制玉米芽长和根长的活性分别提高7.12%～14.27%和6.32%～11.65%,其持效期延长0.46～12.17天:施药后28天,添加0.5%～2.0%的黄腐酸使乙草胺防除稗草的鲜重抑制率提高11.93%～16.88%.     

Characterization of fluorescent Pseudomonas spp. associated with roots and soil of two sorghum genotypes

Sorghum is used as bioenergy feedstock, animal feed, and food. Economical methods for disease prevention and control are valuable for producers. Fluorescent Pseudomonas spp. were isolated from sorghum roots and surrounding soil with the goal of finding isolates that significantly inhibited sorghum fungal pathogens. Fluorescent pseudomonads were collected from seedlings of sorghum cultivars RTx433 and Redlan and wheat cultivar Lewjain, grown in two soils. Lewjain is known to support growth of producers of the antibiotic, 2,4-diacetylphloroglucinol (2,4-DAPG). Isolates from all three plants were assessed for hydrogen cyanide (HCN) and extracellular protease production, and for a 2,4-DAPG gene, phlD. Both soil type and plant type affected HCN- and protease-production, but phlD was not affected. Subsets of phlD ⁺ isolates were chosen to determine phlD genotypes and to conduct in vitro inhibition assays against sorghum pathogens. Most isolates from sorghum and wheat were genotype D, previously associated with superior root colonization. phlD ⁺ sorghum isolates were co-cultured with five sorghum pathogens. One isolate from each sorghum line exhibited inhibition to all five pathogens but more Redlan isolates were inhibitory to the virulent pathogen, Fusarium thapsinum, than RTx433 isolates. Nearly all inhibitory isolates from either sorghum cultivar were from one soil type. This is consistent with what had been previously observed in field studies: that soil type played a significant role in determining characteristics of fluorescent Pseudomonas spp. isolated from roots or soil, but sorghum genotype also had a considerable effect.     

赤霉素缓解Mn~(2+)对草甘膦拮抗效应的研究

为探索能够减轻或消除Mn2+对草甘膦拮抗效应的方法,以高羊茅为试材,将赤霉素(GA3)与草甘膦和硫酸锰(Mn2+质量分数为0.1%)混用,研究了赤霉素对Mn2+降低草甘膦药效的缓解作用。结果表明:赤霉素+草甘膦+硫酸锰处理组高羊茅比同剂量草甘膦+硫酸锰处理组叶色更黄,萎蔫更严重,与同剂量草甘膦单剂处理组比较接近,其中加入50 mg/L赤霉素处理组缓解草甘膦拮抗效应的效果最好。赤霉素+草甘膦+硫酸锰处理组高羊茅的干、鲜重及叶绿素含量均低于草甘膦+硫酸锰处理组,而丙二醛和莽草酸含量均明显高于草甘膦+硫酸锰处理组。处理后第6天,赤霉素+草甘膦+硫酸锰组莽草酸含量分别比草甘膦+硫酸锰组增加了49.8%(加入50 mg/L赤霉素)和28.8%(加入30 mg/L赤霉素),差异显著;处理后第2天,赤霉素+草甘膦+硫酸锰组丙二醛含量分别比草甘膦+硫酸锰组增加了54.1%(加入50 mg/L赤霉素)和52.9%(加入30 mg/L赤霉素),差异显著。研究表明,将赤霉素与锰肥和草甘膦混合喷施,将有可能在一定程度上缓解Mn2+对草甘膦的拮抗效应,保证草甘膦的除草效果。     

Vegetative Growth of Sorghum and Striga hermonthica in Response to Nitrogen and the Degree of Host Root Infection

The effects of nitrogen and the extent of sorghum root infection by Striga hermonthica on host-parasite association during vegetative growth were studied using a split root system in a 3 × 3 factorial combination of N (37mg on one, 18.5 or 37mg on both root-halves) and Striga (no, one or both root-half infection). High N increased sorghum shoot weight by 22% more than low N, but did not significantly affect Striga growth 64 days after transplanting sorghum (DAP). Striga reduced sorghum stem height and weight by 22% and 25% at 38 DAP, and by 34% and 36% at 64 DAP, respectively. Leaf weight was not affected. Striga stimulated root growth 38 DAP, but not 64 DAP. In partially infected sorghum, 64 DAP, the parasite shoot number, shoot height and shoot dry weight were 36%, 46% and 35%, respectively and host shoot dry matter was 142% of those in fully infected plants, indicating an inverse relationship between the degree of host root infection and the level of resistance. The results suggest that sorghum released resistance-confering substances to the infection points after sensing infection. When infection points are widely distributed as in fully infected sorghum, less of such substances appear to render the host more vulnerable.     

Differential phytotoxicity of glyphosate in maize seedlings following applications to roots or shoot

The transport and differential phytotoxicity of glyphosate was investigated in maize seedlings following application of the herbicide to either roots or shoots. One-leaf maize seedlings (Zea mays L.) were maintained in graduated cylinders (250 mL) containing nutrient solution. Half of the test plants were placed in cylinders (100 mL) containing different ¹⁴C-glyphosate concentrations; the remainder received foliar appliation of ¹⁴C-glyphosate. After 26 h, the roots and the treated leaves were washed with distilled water, and the plants placed again in cylinders (250 mL) containing fresh nutrient solution for 5 days. Plants were weighed, and split into root, seed, cotyledon, coleoptile, mesocotyl, first leaf and apex. The recovery of ¹⁴C-glyphosate was over 86%. For both application treatments, the shoot apex was the major sink of the mobilized glyphosate (47.9 ± 2.93% for root absorption and 45.8 ± 2.91% for foliar absorption). Expressed on a tissue fresh weight basis, approximately 0.26 μg a.e. g⁻¹ of glyphosate in the apex produced a 50% reduction of plant fresh weight (ED₅₀) when the herbicide was applied to the root. However, the ED₅₀ following foliar absorption was only 0.042 μg a.e. g⁻¹ in the apex, thus maize seedlings were much more sensitive to foliar application of the herbicide.     

喹草酮与莠去津复配防除杂草效果及对高粱的安全性

为明确对羟基丙酮酸双氧化酶抑制剂类新型除草剂喹草酮应用于高粱田的可行性,于2018-2019年在温室和田间测定喹草酮与莠去津复配的除草效果及对高粱的安全性。温室试验结果表明,喹草酮与莠去津复配对狗尾草Setaria viridis和苘麻Abutilon theophrasti均有很好的防除效果,两者按有效成分用量比1：4~1：7配比对狗尾草的GR₅₀在134.40~168.92 g （a.i.）/hm²之间,明显好于喹草酮和莠去津单独施用时的GR₅₀,分别为150.53g （a.i.）/hm²和589.30g （a.i.）/hm²;两者复配对狗尾草的共毒系数在234.80~311.03之间,远大于120.00,显示出明显的增效作用;对苘麻的共毒系数在140.16~168.38之间,也表现出增效作用;对马唐Digitaria sanguinalis也有较好的防除效果;喹草酮与莠去津按有效成分用量比1：5复配的制剂在最高用量3 600g （a.i.）/hm²处理下,3个高粱品种生长均正常,且对高粱和杂草之间的选择性指数远大于6.59,对高粱的安全性高。田间试验结果表明,喹草酮与莠去津复配应用于高粱田对高粱安全,且对田间杂草野稷Panicum ruderale、虎尾草Rabdosia eriocalys、稗Echinochloa crus-galli、反枝苋Amaranthus retroflexus和藜Chenopodium album等均有极好的防除效果,2018-2019年对高粱田杂草的总株防效分别为94.2%和92.8%,鲜重防效分别为95.6%和94.2%,明显高于药剂对照50%异甲·莠去津悬浮剂土壤处理和37%二氯·莠去津悬浮剂茎叶处理的防除效果。表明喹草酮与莠去津复配应用于高粱田防除杂草效果良好。     

CDAA inhibition of Kaurene oxidation in etiolated sorghum coleoptiles

N,N-Diallyl-2-chloroacetamide (CDAA) (0.25 ppmw; I μM) inhibited growth of 14-day-old sorghum (Sorghum bicolor (L) Moench. cv Funks G 522DR) when the herbicide was incorporated into sand. Kaurene oxidation was inhibited in a cell-free enzyme preparation from 4-day-old unruptured, etiolated coleoptiles. CDAA (1 μM) inhibited incorporation of [¹⁴C]mevalonic acid into kauren-19-oic acid (50%), with resultant increases in concentration of precursors. Thus, inhibition of gibberellin precursor biosynthesis was demonstrated, and this activity would explain many of the morphogenic and biochemical responses of grasses to CDAA.     

The impact of potato cysteine proteinases in plant growth and development

The role of cysteine proteinases in the growth and development of healthy and PVY^NTN infected potato plants (Solanum tuberosum L. cv. ‘Désirée’) and the subcellular localization of a particular potato leaf cysteine proteinase PLCP-2 were studied in tissue culture. The immunolocalization of PLCP-2 on the ultrathin sections of potato plants was examined by electron microscopy. PLCP-2 was found in protein bodies in vacuoles, in cytoplasm and in cell walls of shoot tips, leaves, stems and root tips. PLCP-2 was observed at all locations where its endogenous inhibitors PCPI 6·6 and multicystatin were localized, which indicates the possible regulation of PLCP-2 by these inhibitorsin vivo . In order to study the physiological role of cysteine proteinases in potato plants, their total activity was diminished by introducing Ep-475 into the growth media and further into the plant through root absorption. The morphological characteristics of healthy and PVY^NTN infected plants grown on media with added Ep-475 were followed. The results suggest that cysteine proteinases are involved in the synthesis and transport of plant metabolites and in processes that lead to organogenesis. Observations also indicate that the ratio between cysteine proteinases and their endogenous inhibitors in potato plants is altered after infection with PVY^NTN.