Reduced Shoot Fresh Weight Research Articles

Aminomethylphosphonic acid, a metabolite of glyphosate, causes injury in glyphosate-treated, glyphosate-resistant soybean.

Glyphosate-resistant (GR) soybean [Glycine max (L.) Merr.] was developed by stable integration of a foreign gene that codes insensitive enzyme 5-enolpyruvylshikimate-3-phosphate synthase, an enzyme in the shikimate pathway, the target pathway of glyphosate. Application of glyphosate to GR soybean results in injury under certain conditions. It was hypothesized that if GR soybean is completely resistant to the glyphosate, injury could be caused by a metabolite of glyphosate, aminomethylphosphonic acid (AMPA), a known phytotoxin. Glyphosate and AMPA effects on one- to two-trifoliolate leaf stage (16-18-days old) GR and non-GR soybean were examined in the greenhouse. In GR soybean, a single application of glyphosate-isopropylammonium (1.12-13.44 kg/ha) with 0.5% Tween 20 did not significantly reduce the chlorophyll content of the second trifoliolate leaf at 7 days after treatment (DAT) or the shoot dry weight at 14 DAT compared with Tween 20 alone. A single application of AMPA (0.12-8.0 kg/ha) with 0.5% Tween 20 reduced the chlorophyll content of the second trifoliolate leaf by 0-52% at 4 DAT and reduced shoot fresh weight by 0-42% at 14 DAT in both GR and non-GR soybeans compared with Tween 20 alone. AMPA at 0.12 and 0.50 kg/ha produced injury in GR and non-GR soybean, respectively, similar to that caused by glyphosate-isopropylammonium at 13.44 kg/ha in GR soybean. AMPA levels found in AMPA-treated soybean of both types and in glyphosate-treated GR soybean correlated similarly with phytotoxicity. These results suggest that soybean injury to GR soybean from glyphosate is due to AMPA formed from glyphosate degradation.

Interactions between selenium and sulphur nutrition in Arabidopsis thaliana.

Selenium (Se) is an essential plant micronutrient, but is toxic at high tissue concentrations. It is chemically similar to sulphur (S), an essential plant macronutrient. The interactions between Se and S nutrition were investigated in the model plant Arabidopsis thaliana (L.) Heynh. Arabidopsis plants were grown on agar containing a complete mineral complement and various concentrations of selenate and sulphate. The Se/S concentration ratio in the shoot ([Se](shoot)/[S](shoot)) showed a complex dependence on the ratio of selenate to sulphate concentration in the agar ([Se](agar)/[S](agar)). Increasing [S](agar) increased shoot fresh weight (FW) and [S](shoot), but decreased [Se](shoot). Increasing [Se](agar) increased both [Se](shoot) and [S](shoot), but reduced shoot FW. The reduction in shoot FW in the presence of Se was linearly related to the shoot Se/S concentration ratio. These data suggest (i) that Se and S enter Arabidopsis through multiple transport pathways with contrasting sulphate/selenate selectivities, whose activities vary between plants of contrasting nutritional status, (ii) that rhizosphere sulphate inhibits selenate uptake, (iii) that rhizosphere selenate promotes sulphate uptake, possibly by preventing the reduction in the abundance and/or activity of sulphate transporters by sulphate and/or its metabolites, and (iv) that Se toxicity occurs because Se and S compete for a biochemical process, such as assimilation into amino acids of essential proteins.

Tolerance of mannitol-accumulating transgenic wheat to water stress and salinity.

Previous work with model transgenic plants has demonstrated that cellular accumulation of mannitol can alleviate abiotic stress. Here, we show that ectopic expression of the mtlD gene for the biosynthesis of mannitol in wheat improves tolerance to water stress and salinity. Wheat (Triticum aestivum L. cv Bobwhite) was transformed with the mtlD gene of Escherichia coli. Tolerance to water stress and salinity was evaluated using calli and T(2) plants transformed with (+mtlD) or without (-mtlD) mtlD. Calli were exposed to -1.0 MPa of polyethylene glycol 8,000 or 100 mM NaCl. T(2) plants were stressed by withholding water or by adding 150 mM NaCl to the nutrient medium. Fresh weight of -mtlD calli was reduced by 40% in the presence of polyethylene glycol and 37% under NaCl stress. Growth of +mtlD calli was not affected by stress. In -mtlD plants, fresh weight, dry weight, plant height, and flag leaf length were reduced by 70%, 56%, 40%, and 45% compared with 40%, 8%, 18%, and 29%, respectively, in +mtlD plants. Salt stress reduced shoot fresh weight, dry weight, plant height, and flag leaf length by 77%, 73%, 25%, and 36% in -mtlD plants, respectively, compared with 50%, 30%, 12%, and 20% in +mtlD plants. However, the amount of mannitol accumulated in the callus and mature fifth leaf (1.7-3.7 micromol g(-1) fresh weight in the callus and 0.6-2.0 micromol g(-1) fresh weight in the leaf) was too small to protect against stress through osmotic adjustment. We conclude that the improved growth performance of mannitol-accumulating calli and mature leaves was due to other stress-protective functions of mannitol, although this study cannot rule out possible osmotic effects in growing regions of the plant.

Propanil activity, uptake and metabolism in resistant Echinochloa spp. biotypes

Field resistance of Echinochloa spp. to propanil has been previously reported in Costa Rica, Colombia and Arkansas (USA). In this study, the mechanism of resistance was investigated in three resistant (R) and three susceptible (S) biotypes. The shoot fresh weight reduction in pot‐grown plants from a post‐emergence spray of propanil at 2.44 kg a.i. ha−1 on biotypes R/S from Costa Rica, Colombia and Arkansas was 35/98%, 25/79% and 20/82% respectively. In vitro chlorophyll fluorescence data from leaf tissue incubated in propanil showed that photosynthesis was inhibited in all biotypes, indicating that the propanil‐binding site and enzyme were not altered. After transfer to herbicide‐free solution, photosynthesis recovered only in resistant biotypes, indicating that the mechanism of resistance was caused by enhanced metabolism of the herbicide. Simultaneous treatment with fenitrothion, an aryl acylamidase inhibitor, prevented the recovery of photosynthesis in leaf tissue in two resistant biotypes. In contrast, the cytochrome P450 mono‐oxygenase inhibitor, 1‐aminobenzotriazole, did not prevent recovery from propanil in leaf tissue. Application of 14C‐propanil to the second leaf of intact Echinochloa plants showed that c. 90% of the radioactivity remained in the treated leaf for up to 72 h after application. No major differences in translocation between R and S biotype plants were found. TLC analysis of tissue extracts from the treated leaves showed substantially less radioactivity associated with propanil, present after 72 h in rice or in the three R biotypes, compared with S biotypes.

Nutrient Solution Nitrogen Form and Bird Cherry-Oat Aphid Resistance in Wheat

The form of nutrient solution nitrogen (NH4-N or NO3-N) provided to plants can have profound influence upon the severity of many crop diseases. It is not known if nutrient solution nitrogen form would affect wheat (Triticum aestivum L.) resistance to bird cherry-oat aphids (Rhopalosiphum padi L.). The objectives of our growth chamber experiments were to determine if the form of nitrogen provided in plant nutrient solutions affected aphid population growth parameters or the ability of wheat to withstand infestation. For aphid population growth experiments, winter wheat plants were watered with a complete nutrient solution containing NO3-N or NH4-N for 13 d prior to infestation with nymphs. The time period to adulthood and the number of progeny produced were recorded. For plant growth experiments, spring wheat plants were grown in sand culture using half-strength complete nutrient solution containing NO3-N or NH4-N. Approximately 100 apterous aphids were applied to half of the plants 7 d after germination. Plants were harvested for shoot and root fresh weight measurement 6 days after infestation. Aphid population growth (development time, number of aphids produced, and intrinsic rate of increase) were not significantly affected by nutrient solution N form treatments. Plants grown with NH4-N nutrient solutions had significantly less shoot fresh weight (0.181 g for NH4-N; 0.230 g for NO3-N). Aphid infestation also significantly reduced shoot fresh weight (0.149 g in infested; 0.262 g in control). There were no significant interactions between nutrient solution N form and aphid treatments for shoot fresh weight. Aphid treatment did not reduce root fresh weight in plants given NO3-N nutrient solution (aphid infested = 0.15 g; control = 0.15 g), but did in plants given NH4-N nutrient solution (aphid infested = 0.11 g; control = 0.17 g). Thus, while N form given to wheat plants had no effect on aphid population growth characteristics, plants given NH4-N nutrient solution showed less root growth than plants given the NO3-N nutrient solutions.

Rapid effects of nitrogen form on leaf morphogenesis in tobacco.

Ammonium (NH4+) instead of nitrate (NO3-) as the nitrogen (N) source for tobacco (Nicotiana tabacum L.) cultivated in a pH-buffered nutrient solution resulted in decreased shoot and root biomass. Reduction of shoot fresh weight was mainly related to inhibition of leaf growth, which was already detectable after short-term NH4+ treatments of 24 h, and even at a moderate concentration level of 2 mM. Microscopic analysis of the epidermis of fully expanded leaves revealed a decrease in cell number (50%) and in cell size (30%) indicating that both cell division and cell elongation were affected by NH4+ application. Changes in various physiological parameters known to be associated with NH4(+)-induced growth depression were examined both in long-term and short-term experiments: the concentrations of total N, soluble sugars and starch as well as the osmotic potential, the apparent hydraulic conductivity and the rate of water uptake were not reduced by NH4+ treatments (duration 1-12 d), suggesting that leaf growth was neither limited by the availability of N and carbohydrates, nor by a lack of osmotica or water supply. Although the concentration of K+ in leaf press sap declined in expanding leaves by approximately 15% in response to NH4+ nutrition, limitation of mineral nutrients seems to be unlikely in view of the fast response of leaf growth at 24 h after the start of the NH4+ treatment. No inhibitory effects were observed when NH4+ and NO3- were applied simultaneously (each 1 mM) resulting in a NO3-/NH4+ net uptake ratio of 6:4. These findings suggest that the rapid inhibition of leaf growth was not primarily related to NH4+ toxicity, but to the lack of NO3(-)-supply. Growth inhibition of plants fed solely with NH4+ was associated with a 60% reduction of the zeatine + zeatine riboside (Z + ZR) cytokinin fraction in the xylem sap after 24 h. Furthermore Z + ZR levels declined to almost zero within the next 4 d after start of the NH4+ treatment. In contrast, the concentrations of the putative Z + ZR precursors isopentenyl-adenine and isopentenyl-adenosine (i-Ade + i-Ado) were not affected by NH4+ application. Since cytokinins are involved in the regulation of both cell division and cell elongation, it seems likely that the presence of NO3- is required to maintain biosynthesis and/or root to shoot transfer of cytokinins at a level that is sufficient to mediate normal leaf morphogenesis.

Resistance of barnyardgrass (Echinochloa crus-galli) to atrazine and quinclorac

Two populations of Echinochloa crus-galli (R and I) exhibited resistance to quinclorac. Another population (X) exhibited resistance to quinclorac and atrazine. The R and I populations were collected from monocultures of rice in southern Spain. The X population was collected from maize fields subjected to the application of atrazine over several years. The susceptible (S) population of the same genus was collected from locations which had never been treated with herbicides. The quinclorac ED50 value (dose causing 50% reduction in shoot fresh weight) for the R and I biotypes were 26- and 6-fold greater than for the S biotype. The X biotype was 10 times more tolerant to quinclorac than the S biotype and also showed cross-resistance to atrazine, being 82-fold more resistant to atrazine than the R, I and S biotypes. Chlorophyll fluorescence and Hill reaction analysis supported the view that the mechanism of resistance to atrazine in the X biotype was modification of the target site, the DI protein. Quinclorac at 20 mg litre-1 did not inhibit photosynthetic electron transport in any of the test biotypes. The quinclorac I50 values (herbicide dose needed for 50% Hill reaction reduction) of the S population was over 50000-fold higher than the atrazine I50 value for the same S population, indicating that quinclorac is not a PS II inhibiting herbicide. Propanil at doses greater than 0·5 kg ha-1 controlled all the biotypes. © 1997 SCI

Identification of Sulfometuron-Resistant Italian Ryegrass (Lolium multiflorum) Selections

Two sulfometuron-resistant biotypes of Italian ryegrass were identified from rights-of-way of U.S. Highway 49E in Holmes County, MS, and State Highway 14 in Humphreys County, MS. Sulfometuron at 5.2 g ai/ha applied PRE or POST reduced shoot fresh weight of these selections 20% or less at 4 wk after treatment. A susceptible ‘Gulf’ Italian ryegrass was reduced 52% or more in shoot fresh weight by 0.5 g/ha sulfometuron applied PRE or POST The biotype from Highway 49E was reduced 47% or less in shoot fresh weight by 520 g/ha sulfometuron applied PRE or POST.

Phenmedipham-Ozone Pollution Interactions in Sugarbeet (Beta vulgarisL. cv. Saxon): A Physiological Study

Actively growing sugarbeet is treated with the post-emergent herbicide phenmedipham at times when ozone pollution episodes are likely to occur. There is a possibility of an interaction occurring between ozone and phenmedipham as both treatments produce similar effects in susceptible plants, such as a reduction in growth and photosynthesis and an increase in the activities of endogenous antioxidant enzymes. To investigate this likelihood, laboratory experiments were conducted in which two- to three-leaf sugarbeet plants (Beta vulgaris L. cv. Saxon) were exposed to a simulated two-day ozone episode (100 nl litre -1 , 7 h day -1 ) followed three days later by treatment with field rate phenmedipham (1.14 kg AI ha -1 ). Growth analysis indicated that an interaction was occurring in which plants treated with ozone and phenmedipham had less reduction in shoot fresh weight than expected. Exposure to phenmedipham alone or ozone followed by phenmedipham reduced net photosynthesis by over 50% and transpiration rate by 30%. The activities of antioxidant enzymes such as catalase, guaiacol peroxidase and superoxide dismutase were stimulated by both treatments individually, but to a greater extent when ozone and phenmedipham were combined. For example, three days after herbicide treatment, the activity of superoxide dismutase increased by 20% in plants treated with ozone alone, 20% in plants treated with phenmedipham alone and 85% in plants that were treated with ozone followed by phenmedipham. We conclude that ozone pollution may predispose sugarbeet to tolerate the herbicide phenmedipham by enhancing the activity of the endogenous antioxidant detoxification enzyme system.

Evidence for a Causative Role of Cyanide, Derived from Ethylene Biosynthesis, in the Herbicidal Mode of Action of Quinclorac in Barnyard Grass

Root application of the quinolinecarboxylic acid herbicide quinclorac to barnyard grass ((Echinochloa crus-galli (L.) P. Beauv.) caused inhibition of shoot growth accompanied by chlorosis and necrosis. After 1 day of exposure, cyanide levels in the shoot tissue increased according to the concentration of the herbicide and the time of its application and closely correlated with the reduction in shoot fresh weight. Four days after the application of 10 and 100 μM quinclorac, the respective cyanide levels in the shoot tissue were approximately two and three times higher than controls and reached a maximum of 40 μM. Increases in β-cyanoalanine synthase activity, the main HCN detoxifying enzyme, ethylene production, and in the endogenous levels of 1-aminocyclopropane-1-carboxylic acid (ACC) preceded cyanide accumulation, When ACC was exogenously supplied to detached shoots of barnyard grass via the vascular system, its accumulation within the tissue coincided with increases in ethylene formation and cyanide content. Both metabolites of ACC appeared to be formed in stoichiometrically equivalent amounts. Root treatment of intact plants with KCN caused concentration-dependent increases in the levels of cyanide found in the shoot tissue which inversely correlated with the changes in fresh weight. The concentrations of quinclorac or KCN applied via the roots which led to twofold increases in the cyanide levels of the shoots had similar effects on the shoot fresh weight, causing reductions of nearly 30%. The phytotoxic symptoms, chlorosis and necrosis, were also similar. In contrast, phytotoxic tissue sensitivity to ethylene released by applied 2-chloroethylphosphonic acid (ethephon) was only very low. It is concluded that cyanide, derived ultimately from quinchlorac-stimulated ACC synthesis, is a causative factor in the herbicidal effects observed in the shoots of barnyard grass.

5424271 Strains of Drechslera spp., weed control compositions containing the same and methods for controlling weeds using the same: Yamaguchi Kenich; Arita Masanobu; Gohbara Masatosh; Shinmi Tatsuo; Fukui Keiko; Tohyama Emi Mobara, Japan Assigned to Mitsui Toatsu Chemicals Inc

Root application of the quinolinecarboxylic acid herbicide quinclorac to barnyard grass ((Echinochloa crus-galli (L.) P. Beauv.) caused inhibition of shoot growth accompanied by chlorosis and necrosis. After 1 day of exposure, cyanide levels in the shoot tissue increased according to the concentration of the herbicide and the time of its application and closely correlated with the reduction in shoot fresh weight. Four days after the application of 10 and 100 μM quinclorac, the respective cyanide levels in the shoot tissue were approximately two and three times higher than controls and reached a maximum of 40 μM. Increases in β-cyanoalanine synthase activity, the main HCN detoxifying enzyme, ethylene production, and in the endogenous levels of 1-aminocyclopropane-1-carboxylic acid (ACC) preceded cyanide accumulation, When ACC was exogenously supplied to detached shoots of barnyard grass via the vascular system, its accumulation within the tissue coincided with increases in ethylene formation and cyanide content. Both metabolites of ACC appeared to be formed in stoichiometrically equivalent amounts. Root treatment of intact plants with KCN caused concentration-dependent increases in the levels of cyanide found in the shoot tissue which inversely correlated with the changes in fresh weight. The concentrations of quinclorac or KCN applied via the roots which led to twofold increases in the cyanide levels of the shoots had similar effects on the shoot fresh weight, causing reductions of nearly 30%. The phytotoxic symptoms, chlorosis and necrosis, were also similar. In contrast, phytotoxic tissue sensitivity to ethylene released by applied 2-chloroethylphosphonic acid (ethephon) was only very low. It is concluded that cyanide, derived ultimately from quinchlorac-stimulated ACC synthesis, is a causative factor in the herbicidal effects observed in the shoots of barnyard grass.

Growth Inhibition of Caladium by High Temperature

Nonplanted Caladium × hortukmum Birdsey `Candidum' tubers were exposed to 26 (control), 38,43, or 48C for 1,2, or 3 days. Then tubers were planted and forced in a glasshouse for 4 weeks at 18 to 33C (air). Leaf emergence from tubers exposed to 48C for 1 or 2 days required 3-12 days longer than leaf emergence from control tubers. No leaves emerged from tubers treated at 48C for 3 days. Exposing tubers to 38C for 3 days or 43C for 1 day did not affect subsequent plant growth. Exposing tubers to 43C for 2 or 3 days or 48C for 1 or 2 days resulted in plants with reduced shoot fresh weights and fewer leaves ≥ 15 cm. In a second experiment, planted tubers were forced for 10 days at 26C so that roots had developed to the edge of the pot and shoots had emerged to the soil surface. These planted (sprouting) tubers were exposed to 43C for 0,4,8,12,16,20, or 24 hours/day for 1,3, or 5 days and then forced for 7 weeks in a glasshouse. With 3- or 5-day treatments, days to leaf emergence increased as the hours of exposure to 43C increased. Only 33% of planted tubers exposed to 43C for 24 hours/day for 5 days sprouted. Tubers exposed to 43C for≤ 12 hours/day for 3 days produced plants of similar or greater height, numbers of leaves □≥15 cm wide, and shoot fresh weights, but additional hours of daily exposure decreased these plant characteristics. At 5 days, plant height, number of ≥ 15-cm-wide leaves, and shoot fresh weight decreased linearly with increased hours of exposure of tubers to high temperature.

INHIBITION OF GROWTH OF CALADIUM BY HIGH TEMPERATURE

Caladium × hortulanum Birdsey `Candidum' tubers were exposed to 26, 38, 43 and 48C for 1, 2 and 3 days. Tubers were then forced in a glass-glazed greenhouse. Tubers exposed to 48C for 1 and 2 days required significantly longer to emerge than all other temperature treatments, while tubers exposed to 48C for 3 days failed to emerge. After 4 weeks of growth, exposure of tubers to 43C for 2 and 3 days and 48C for all time periods resulted in plants with reduced shoot fresh weights and fewer leaves with a width greater than 15 cm. After roots developed to the edge of the pot and shoots emerged (10 days after potting), potted tubers were exposed to 43C for 0, 4, 8, 12, 16, 20 and 24 hours per day for 1, 3 and 5 days. Potted tubers exposed to 43C for 8 or more hours per day for 3 days and 12 hours or more for 5 days were significantly delayed in emergence. Only 33% of potted tubers exposed to 43C for 24 hours per day for 5 days emerged. Exposure to 43C for 1 and 3 days resulted in increased shoot fresh weights for exposures up to 12 hours per day. As the exposure time per day increased, shoot fresh weights decreased. Exposure of potted tubers to 43C for 16 hours or more per day for 3 days reduced plant height and the number of leaves with a width greater than 15cm. Regardless of the number of hours of exposure per day, potted tubers exposed to 43C for 5 days had reduced shoot fresh weights and fewer leaves with a width greater than 15cm as compared to unexposed potted tubers. As the number of hours of exposure per day increased, shoot fresh weight and the number of leaves with a width greater than 15cm decreased.

Interactions of Foliarly Applied Herbicides on Three Weed Species in Peanut (Arachis hypogaea)

In the greenhouse, naptalam at 1.1 to 4.5 kg ai ha−1antagonized activity of paraquat at 0.04 to 0.14 kg ai ha−1in 14 of 16 rate combinations when applied to sicklepod. Sicklepod shoot fresh weight reduction was less compared to that obtained with paraquat alone when paraquat at 0.04 kg ha−1was mixed with bentazon at 0.42 to 0.84 kg ai ha−1or monocarbamide dihydrogensulfate at 14 to 58 kg ai ha−1. Paraquat activity on Florida beggarweed was antagonized by mixtures of paraquat at 0.04 or 0.07 kg ha−1with bentazon at 0.63 or 0.84 kg ha−1or paraquat at 0.04 to 0.14 kg ha−1with naptalam at 3.4 or 4.5 kg ha−1. Mixtures of lactofen at 0.06 to 0.22 kg ai ha−1with monocarbamide dihydrogensulfate at 14 kg ha−1or lactofen at 0.06 or 0.16 kg ha−1with alachlor at 1.4 to 2.8 kg ai ha−1synergistically increased tall morningglory shoot fresh weight reduction. In the field, excellent sicklepod shoot fresh weight reduction by paraquat applied alone masked most antagonistic effects of paraquat mixtures. Addition of alachlor to monocarbamide dihydrogensulfate at 29 kg ha−1improved activity on sicklepod compared to monocarbamide dihydrogensulfate applied alone.

Spread of endomycorrhizal colonization and effects on growth of apple seedlings

SUMMARYAn experiment to determine the short‐term characteristics of root colonization by two vesicular‐arbuscular (VA) mycorrhizal fungi with apple (Malus × domestica Borkh.) was initiated concurrently with an experiment to determine longer‐term effects of colonization by these fungi on the growth of apple seedlings. Short‐term characteristics of colonization were determined by sequential harvesting of a cuvette system which also allowed monitoring of hyphal spread from inoculated ‘spreader’ plants, through a root‐free soil region, to non‐inoculated ‘receiver’ plants. Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe exceeded Glomus macrocarpum Tul. & Tul. in rate of initial colonization, amount of maximum colonization, and persistence of arbuscules and external hyphae. Colonization by either fungus reduced shoot fresh weight 11 days after inoculation but increased shoot and total fresh weight by day 38. Hyphae of G. mosseae had traversed through 2 and 3 cm of root‐free soil to colonize non‐inoculated ‘receiver’ roots by 29 days, and hyphae of G. macrocarpum by 38 days. G. mosseae colonized ‘receiver’ roots more intensely than did G. macrocarpum at 2 and 3 cm, and 3 and 4 cm distance, at subsequent harvests. The fungi were effective, singly and in combination, in increasing apple plant biomass, as compared to non‐mycorrhizal controls. Relative height growth rate, and colonization at harvest, of G. macrocarpum‐inoculated plants were less than those of G. mosseae‐inoculated or G. mosseae + G. macrocarpum‐ inoculated plants, but greater than those of the non‐mycorrhizal control trees.

Influence of Site of Uptake of Fluridone on Early Development of Soybean (Glycine max) and Cotton (Gossypium hirsutum)

The double pot technique was used to study the effects of uptake site of fluridone {1-methyl-3-phenyl-5-[3-(trifluoromethyl—phenyl]-4(1H)-pyridinone} on early shoot and root development of soybean [Glycine max(L.) Merr. ‘Williams’] and cotton (Gossypium hirsutumL. ‘Acala SJ-1′). Soybean is susceptible and cotton is resistant to fluridone. Root uptake in soybean resulted in increased shoot length in the epicotyl and shoot apex, reduced shoot fresh weight, chlorosis of primary and trifoliolate leaves, as well as reduced root length, branching, and fresh weight. Shoot uptake resulted in reduced shoot length above the hypocotyl, reduced shoot weight, severe chlorosis of primary leaves, and inhibition of trifoliolate leaf formation. The reduction in the root length, branching, and weight was less by shoot uptake than by root uptake. In cotton, root uptake resulted in reduced shoot length in the epicotyl and shoot apex, slight reduction in shoot weight, no effect on chlorosis of cotyledon leaves, moderate to slight chlorosis of the true leaves, and no effect on root length, branching, or fresh weight. Shoot uptake resulted in reduced length of all shoot components and shoot weight, chlorosis of cotyledon leaves and the true leaves, and reduced root length, branching, and weight. Compared to soybean, cotton required much higher fluridone concentrations to show the above effects. It was generally concluded that in soybean, uptake by both the root and the shoot contributed significantly to the injury, whereas in cotton, shoot uptake was relatively more important.