Corn Root Growth Research Articles

Availability and Persistence of Imazaquin, Imazethapyr, and Clomazone in Soil

The availability and persistence of imazaquin, imazethapyr, and clomazone were studied in a Cisne silt loam (1.3% organic matter) and a Drummer silty clay loam (5.8% organic matter). Availability of all three herbicides to bioassay species was greater in the Cisne soil than in the Drummer soil. Corn root growth was more sensitive to imazaquin and imazethapyr than corn shoot growth. Shoot and root growth of wheat was inhbited by similar clomazone concentrations. In field experiments conducted in 1984, 1985, and 1986, all three herbicides were more persistent in the Drummer silty clay loam than in the Cisne silt loam. Clomazone and imazethapyr were detected by liquid or gas chromatographic analysis in the Drummer soil 3 yr following application. Crop injury occurred 5 months after application of imazaquin and clomazone to the Drummer soil. In the Cisne soil, only imazethapyr caused crop injury 5 months after application. Herbicide residues found below 7.5 cm were greater in the Drummer soil than in the Cisne soil.

Density and Spatial Pattern of Propagules ofMacrophomina phaseolinain Corn Rhizospheres

For frequency count data of propagule density, the Poisson distribution was appropriate in 18 of 40 and 20 of 40 cases for location A and B, respectively; however, the negative binomial distribution did not describe any data set. Because density and spatial pattern of propagules of M. phaseolina were generally similar throughout the growing season, this suggests either a lack of detectable reproductive activity and decay of propagules in soil during periods of active corn root growth or equal rates of propagule reproduction and death

Effect of conservation tillage systems on corn root growth

The effects of conservation tillage on crop production have been widely investigated, but less information is available on root growth with different tillage systems over a range of soils. In this study, we compared corn ( Zea mays L.) root length density and distribution with conventional moldboard plowing (MP) and 3 conservation-tillage treatments: chisel plowing (CH); ridge-tillage (RT); no-tillage (NT); for Griswold and Kewaunee silt loam and Plainfield loamy-sand soils. Root length densities were determined for the row (R), non-wheel track (NWT) and wheel track (WT) positions for two growing seasons (1982 and 1983). Conservation-tillage systems had equal or higher root densities than MP for all positions and depths at all 3 sites. Maximum root densities occurred between 10 and 40 cm for all tillage systems at all locations. In most cases, reduced root growth was associated with wheel traffic positions. Wheel traffic reduced root densities in the surface 10 cm by as much as 52% in MP at the Plainfield site.

Corn Root Growth and Nitrogen Uptake as Affected by Ammonium Placement

AbstractStimulation of root growth in the N‐fertilized soil volume of placed N fertilizer has been observed, but no quantitative data are available. The objective of this research was to obtain quantitative data on the influence of the fractional soil volume fertilized with NH+4 on corn (Zea mays L.) root distribution between NH+4‐fertilized and unfertilized soil, and to determine the effect of N placement on N uptake and plant growth. A pot experiment with seven treatments and three replicates was conducted using Raub silt loam (fine silty, mixed, mesic Aquic Argiudolls). The treatments were six volume fractions of 1.00, 0.50, 0.20, 0.10, 0.05, and 0.02 of soil fertilized with NH+4 plus a no‐N treatment. Before use, the soil was leached to remove NO−3 and a nitrification inhibitor was added. The NH+4 rate was 90 mg N kg−1 of soil in the pot. Six‐day‐old corn plants were transplanted into pots with 3 kg of soil and grown for 14 d, and into pots with 15 kg of soil and grown for 40 d. Corn was grown for 14 d with all treatments and for 40 d with the 0.2 placement. Root length density (km m −3) was greater in the NH+4‐fertilized soil. Root distribution between the NH+4‐fertilized and unfertilized soil volumes, the same at 14 d and 40 d, can be described by the equation y = x0.70 (r2=0.99), where y is the fraction of total root length in the NH+4 ‐fertilized soil when NH+4 is mixed with x fraction of the soil. The effect of NH+4 on root distribution was similar to that observed in earlier studies with P. Shoot N concentration was not affected by NH+4 placement; however, plant weight and N uptake were less with the 0.5 and 0.2 placement treatments.

Effects of Napropamide on Growth and Anatomy of Corn,Zea mays, Roots

Structural studies were conducted to evaluate the effects of napropamide on the growth and development of corn roots. At 1.0 and 10.0 μM napropamide, root growth was inhibited severely within 3 days of seed germination. Root diameter within 1 mm of the root apex doubled and numerous lateral root primordia were observed within 10 mm of the meristem tip in treated roots. The number of cortical parenchyma cell files, xylem vessel, and phloem sieve tube strands also significantly increased. Average cortical cell size did not change, regardless of the treatment. A lateral expansion of the meristematic region of the root coincided with a slight reduction in meristem length but resulted in an overall increase in meristem volume. However, enlargement of the meristem occurred despite a reduction in the number of mitotic figures in the root meristem. Treatment of excised root tips for 24 h with 20 μM napropamide reduced the number of mitotic figures 84%.

Application of fiber optic techniques in underground observations

Two major procedures involving the use of a fiber optic borescope were established for the purpose of: 1. in situ root growth monitoring and 2. iron ochre inspection in subsurface drainpipes. The root image obtained was used to calculate root length using the Newman grid method. The effects of groundwater levels on root growth of silage corn were clearly indicated by the calculated root intensities (length per unit area). Further quantification of root intensities could be achieved using photographic images in a video digitizing process. Iron ochre in a subsurface drainage system was visually inspected. The severity of ochre occurrence was easily estimated from photographic images. The results suggest that permanent observation holes for routine maintenance purposes may be beneficial in future drainage system design.

Compaction and Nitrogen Placement Effect on Root Growth, Water Depletion, and Nitrogen Uptake

AbstractZones of compaction and/or high nutrient concentration that exist with selected tillage systems can alter plant root growth. It is hypothesized that these alterations affect water and nutrient uptake patterns. A greenhouse experiment was conducted to study the effects of horizontally and vertically oriented compaction zones and nitrogen (N) fertilizer placement on corn (Zea mays L.) root growth patterns, soil water depletion, and N fertilizer uptake. Compaction treatments included a simulated plow pan, simulated wheel tracks in one or both interrows, and uncompacted soil. 15N‐enriched ammonium nitrate was point injected 0.1‐m deep at a rate of 80 kg N ha−1 either under the plant or in a simulated interrow region (0.13 m to the side of the plant); a check treatment (no N) was also included. Compaction and N treatments were factorially combined in five randomized blocks. Corn plants were grown for 26 d without rewatering. Measurements taken at 26 d included: shoot and root growth, plant 15N content, and soil water content, and distribution. Compaction treatments did not significantly affect total root growth, but N fertilization tended to decrease it. Root growth compensation, both enhancement in zones of favorable nutrient supply and redirection of growth to zones of more favorable physical conditions, was observed. Nitrogen placement had a greater impact on N uptake when compaction zones were present than when they were not present. Water extraction from a given zone was directly related to root density in that zone.

METSULFURON USE IN BARLEY AND RESIDUAL EFFECT ON SUCCEEDING CROPS

Experiments conducted over 4 yr (1982–1985) determined the efficacy of metsulfuron for use in spring barley (Hordeum vulgare L. ’Volla’) and effects of herbicide residues on crops grown the next season. Barley tolerated metsulfuron at rates up to 72 g a.i. ha−1 with no significant effects on yield but 1000-kernel weight was significantly reduced in two of the three barley crops grown. Control of lamb’s-quarters (Chenopodium album L.) and low cudweed (Gnaphalium uliginosum L.) was acceptable and that of corn spurry (Spergula arvensis L.) and shepherd’s-purse (Capsella bursa-pastoris (L.) Medic.) better than the standard MCPA amine treatment. There was no significant effect on marketable and total yield of rutabaga (Brassica napobrassica Mill.) or potato (Solanum tuberosum L.) and none on total yield of silage corn (Zea mays L.) when each was grown the season after metsulfuron use. Reductions in corn root growth were noted in bioassay tests as late as 120 d after metsulfuron application but the lack of effects on yields of succeeding crops would indicate that the remaining residues were broken down or diluted by plowing and working the soil.Key words: Metsulfuron, barley, potato, rutabaga, silage corn, persistence

Physiological Responses to Sethoxydim in Tissues of Corn (Zea mays) and Pea (Pisum sativum)

The physiological responses of corn (Zea maysL. ‘Goldencrossbantam′) and pea (Pisum sativumL. ‘Alaska′) to sethoxydim {2-[1-(ethoxyimino)butyl]-5-[2-(ethylthio) propyl]-3-hydroxy-2-cyclohexen-1-one} were investigated. Sethoxydim did not affect excised pea root growth at 1 × 10−4M but inhibited excised corn root growth at concentrations of 1 × 10−8M and above. Treating corn impeded root growth with 1 × 10−7M sethoxydim within 4 h after treatment; however, little histological change of the roots was observed at 48 h. At 1 × 10−6M, growth nearly stopped within 4 h after treatment, and clear cytological changes of the roots were observed at 24 and 48 h. Sethoxydim inhibited both mitosis and DNA synthesis of excised corn root tips between 4 and 48 h after treatment. Respiration of corn roots measured by oxygen uptake and the TTC (2,3,5-triphenyltetrazolium chloride) test was not affected by the herbicide directly. Sethoxydim (1 × 10−4M) inhibited IAA-induced cell elongation of corn coleoptile and pea epicotyl by 37 and 12%, respectively. Sethoxydim selectively inhibited the growth of excised root tips of susceptible corn by affecting cell division rather than cell enlargement, and the inhibition mechanism of cell division (inhibition of mitosis) by the herbicide was not by direct inhibition of DNA synthesis or by effects on respiration.

EFFECTS OF SUBSOIL BULK DENSITY, NUTRIENT AVAILABILITY AND SOIL MOISTURE ON CORN ROOT GROWTH IN THE FIELD

In a 4-yr study, root growth in the upper 50 cm of a silt loam soil (Gleyed Melanic Brunisol) was equal to or greater than that in a low-density artificial medium (soil:peat:perlite) in spite of a high bulk density in the soil (1.5 Mg m−3 in the 15-to 45-cm depth). We suggest that, due to the natural structure of the Bm horizon, the resistance to root growth is much less than would be expected from bulk density or penetrometer resistance measurements. Marked increases in P and K fertility in the surface soil had only minor effects on either the total length or distribution of roots although the shoot growth was markedly increased. Neither total root length nor root distribution were altered by irrigation during 1981, the only year a moisture variable was included. During a 2-wk dry period in July, prior to anthesis, soil water potential on the nonirrigated plots decreased to −1.5 MPa in the upper 15 cm and to −0.5 MPa in the 15- to 30-cm layer. Leaf water potential, stomatal conductance and rate of growth during the period were lower on the nonirrigated treatment although final dry matter production was not. The results indicate that corn root growth and distribution in the field are not as sensitive to environmental factors as one would expect from short-term laboratory studies. Key words: Corn, root growth, soil bulk density, fertility, soil water

Corn Root Growth and Distribution as Influenced by Tillage and Nitrogen Fertilization1

AbstractTillage alters both soil physical and chemical properties, which in turn alter the environment for root growth and may impact on plant growth, nutrient uptake, and yield. The objective was to compare corn (Zea mays L.) root morphology and distribution in plots under minimum tillage (MT) for 7 yr to conventional tillage (CT) at N fertilization treatments of 0 and 180 kg N/ha. The 3‐yr field study was conducted in the Maryland Piedmont area on a Delanco silt loam (Aquic Hapludult). Three soil cores per plot were taken at vegetative, silking, and dough stages of plant development. A 76‐ mm‐diam steel tube was used to sample to a depth of 0.6 m in the plant row, at midrow (0.38 m), and half way between (0.19 m). The roots collected to 0.6 m accounted for an average of 82% of the total root weight present after grain harvest. Tillage did not significantly affect plant growth or grain yield. Conventional tillage significantly increased root dry weight in only 1 yr. Minimum tillage and N fertilization both increased root weight in the 0‐ to 0.07‐m layer in 2 of the 3 yr. Root mass decreased 90% in the 0‐ to 0.07‐m depth when samples were compared from in the row to 0.19 m away. Nitrogen fertilization decreased milligrams per meter of root and root radius in 2 of the 3 yr, allowing root length to increase in response to N without altering the weight of roots. Root growth was observed under drought and N stress conditions when shoot growth and yield were limited. The period of most rapid root development occurred in the 8 weeks following planting.

Yearly variation of root distribution with depth in relation to nutrient uptake and corn yield

Abstract Root length and root distribution in the soil profile is important in determining the amount of nutrients and water taken up by the plant. Data about year to year variation of corn (Zea mays L.) root growth and its relation to nutrient uptake are limited. An evaluation of the importance of root system size and distribution on P and K uptake and corn yield was made from samples taken annually from a long‐term fertility experiment on Raub silt loam, fine silty, mixed, mesic Aquic Argiudolls. Root density varied with soil depth among years, whereas P and K fertilizer treatment had no measureable influence on total root length. Ear leaf P concentration was highly correlated with the amount of roots in the 0 to 15 cm layer which contained most of the available P. Since P was not appreciably limiting corn yield, no significant relation was found between yield and P content of the ear leaf. Yields on K deficient plots were positively correlated with root density in the topsoil. Correlations of root dens...

Reciprocal Antagonism between the Herbicides, Diclofop-Methyl and 2,4-D, in Corn and Soybean Tissue Culture

The antagonistic interaction between the grass herbicide, diclofopmethyl (methyl 2-[4(2',4'-dichlorophenoxy)phenoxy]propanoate) (DM), and 2,4-dichlorophenoxyacetic acid (2,4-D), was demonstrated in DM-resistant soybean (Glycine max [L.] Merr.) and DM-susceptible corn (Zea mays L.). 2,4-D caused root shortening and thickening, and induced callus growth in soybean and corn root tissue cultures at 1 and 10 micromolar. Normal soybean root growth was unaffected by 10 micromolar DM whereas corn root growth was inhibited completely by 1 to 10 micromolar DM. DM at 10 micromolar reversed completely the induction of callus growth by 1 micromolar 2,4-D in soybean roots. In corn, 10 micromolar 2,4-D reversed the growth inhibiting activity of 1 micromolar DM and induced callus growth. The antagonistic interaction between DM and 2,4-D was reciprocal and the activity of either compound depended upon the relative concentration of the other. 2,4-D did not antagonize or decrease the activity of DM by decreasing its uptake by root tissues or increasing the rate of its detoxication. The antagonistic interaction between DM and 2,4-D probably involves involves cellular activity associated with actively growing and proliferating cells and requires the presence of both compounds at the sensitive site.

Possible Linkage between NADH-Oxidation and Proton Secretion inZea maysL. Roots

A possible involvement of two different systems in proton translocation and the correlation of this factor to growth rates were measured simultaneously by means of a pH stat and an optical system. Ferricyanide, which can accept electrons at the plasmalemma, led to an immediate increase of net H+ -efflux but also decreased root growth rate. The reduced form, ferrocyanide, inhibited net H+ -effluxwithout changing the growth rate. Thus, corn root growth was not determined by proton secretion exclusively. Vanadate strongly inhibited net H+ -efflux by the roots but did not prevent the stimulating effect of fcrricyanide. Moreover, the extent of enhancement of net H+ -effluxby ferricyanide was exactly the same in vanadate pretreated as in untreated roots. Alcohols were used to try to increase the intracellular NADH level through the action of the cytoplasmic alcohol dehydrogenase present in the roots and coleoptiles. Alcohols, known to be substrates for alcohol dehydrogenase such as propan- 1-ol, ethanol and butan-l -ol increased net H+ -effluximmediately but methanol and secondary alcohols which are not substrates had no effect on proton secretion. The Km values of alcohol dehydrogenase for the alcohols correspond only partly to their effects on proton secretion. However, the specificlty observed suggests that increased H+ -efflux arose from reduction of endogenous NAD by ADH and consequent increased membrane NADH-oxidasc activity trans locating protons and electrons out of the cells. Decreased oxygen concentrations slowed proton secretion at values far higher than are necessary to saturate cytochrome c oxidase. The results of these experiments suggest two distinct systems contributing to proton efflux.

A Corn (Zea mays L.) Bioassay Technique for Measuring Chlorsulfuron Levels in Three Saskatchewan Soils

Chlorsulfuron {2-chloro-N-[[(4-methoxy-6-methyl-1,3,5-triazin-2-yl)amino]carboxyl]benzenesulfonamide} has recently been registered for the control of several broadleaf weeds in spring wheat (Triticum aestivum L.), durum wheat (Triticum durum Desf.), and barley (Hordeum vulgare L.) in western Canada. Residue carryover of this herbicide can cause injury to subsequent sensitive crops. A bioassay technique based on growth of pregerminated corn roots was used to detect levels of chlorsulfuron as low as 0.125 ppb in three Saskatchewan soils. Confidence levels of 95% were established. These confidence bands allowed the detection of chlorsulfuron levels within a minimum and maximum variation of 3.1 and 11.5% of root development.

Effect of soil moisture and phosphate level on root hair growth of corn roots

Root hairs have been shown to enhance P uptake by plants growing in low P soil. Little is known of the factors controlling root hair growth. The objective of this study was to investigate the influence of soil moisture and P level on root hair growth of corn (Zea mays L.). The effect of volumetric soil moistures of 22% (M0), 27% (M1), and 32% (M2) and soil (Raub silt loam, Aquic Argiudoll) P levels of, 0.81 (P0), 12.1 (P1), 21.6 (P2), 48.7 (P3), and 203.3 (P4) μmol P L−1 initially in the soil solution, on shoot and root growth, P uptake, and root hair growth of corn was studied in a series of pot experiments in a controlled climate chamber. Root hair growth was affected more by soil moisture than soil P. The percentage of total root length with root hairs and the density and length of root hairs on the root sections having root hairs all increased as soil moisture was reduced from M2 to M0. No relationship was found between root hair length and soil P. Density of root hairs, however, was found to decrease with an increase in soil P. No correlation was found between root hair growth parameters and plant P content, further suggesting P plays a secondary role to moisture in regulating root hair growth in soils. The increase in root hair growth appears to be a response by the plant to stress as yield and P uptake by corn grown at M0 were only 0.47 to 0.82, and 0.34 to 0.74, respectively, of that measured at M1 across the five soil P levels. The increase in root hair growth at M0, which represents an increase of 2.76 to 4.03 in root surface area, could offset, in part, the reduced rate of root growth, which was the primary reason for reduced P uptake under limited soil moisture conditions.

Comparison of root and root hair growth in solution and soil culture

Abstract Aerated solution culture is frequently used for studying plant growth. Few comparisons have been made of root growth in solution with that found in soil. The objective of this study was to compare root growth and root hair development in these two mediums. Corn (Zea mays L.) grown in aerated solution at two temperatures (18 and 25°C) and three P concentrations (2, 10, and 500 μmol L‐1) was compared with that in three soils, Raub (Aquic Argiudoll) and two Chalmers (Typic Haplaquoll) silt loams, in a controlled climate chamber over 21d. Corn plant weight and root growth were similar in solution culture and Raub soil when grown at an air and soil temperature of 18°C. At 25°C both yield and root growth were greater in Raub soil, even though P uptake by corn was 7‐fold greater in solution culture. The same difference was found when corn grown at 25°C in solution culture at 3 different P concentrations was compared with that grown in Chalmers soil at two P levels. Percentage of total root length with root hairs, root length and density and consequently root surface area, were all greater in the Chalmers soil than in solution culture. An increase in soil P, resulted in a decrease in root hair growth. No such relationship was found in solution culture. Although the recovery and measurement of plant roots and root hairs is more convenient in solution culture, results from this study indicate that the usefulness of solution culture for determining those factors which control root growth and root hair development in soil is limited.

Unharvested Peanut Pods as a Potential Source of Inoculum of Soilborne Plant Pathogens

Unharvested Peanut Pods as a Potential Source of Inoculum of Soilborne Plant Pathogens

Influence of Subsurface Irrigation and Organic Additions on Top and Root Growth of Field Corn1

AbstractNumerous attempts have been made to increase root proliferation by modifying soil profiles possessing undesirable chemical and physical properties.Field and laboratory studies were conducted over a 5‐year period on an Evesboro loamy sand (mesic, coated Typic Quartzipsamments) soil from Delaware to determine the effect of organic additions and type of irrigation on corn (Zea mays L.) grain yield, root distribution, and on selected soil properties. The study also sought to determine if organic additions would increase the effectiveness of subsurface irrigation. Organic additions, made only in the 1st year of the study, consisted of 10 ✕ 40 cm chisel (C) openings at 76 cm intervals which were filled with solid waste (SW) and/or poultry manure (PM) at 65 metric tons/ha. No attempt was made to superimpose corn rows directly above the chisel openings. Irrigation types were subsurface (SSI), and trickle irrigation (TI). Grain yields were significantly higher in C + SSI than in C + TI treatments. Chiseling + SSI increased the average 5‐year corn yield 4,300 kg/ha over C alone which demonstrated the pronounced effect that SSI had on yield. Organic additions had no signifciant effect on grain yields, although yields for the C + SW treatment were numerically higher than for the C + PM treatment each year of the study, and the former averaged 1,150 kg/ha higher over the 5‐year period. The C + SW treatments also produced higher yields than the control (NC). Chiseling, without incorporation of organic materials (C) was no more effective than leaving the soil undisturbed (NC). Organic additions enhanced root growth more than yield of corn. The subsoil was essentially devoid of roots without chiseling or organic additions. The highest CEC and organic matter levels at the end of the 5‐year study were found in the organic addition trench adjacent to the SSI lines. Corn roots proliferated in this region and in most cases enveloped the irrigation lines. Lateral as well as vertical movement of Ca, K, Mg, and P occurred with the lowest concentrations occurring in the plow layer. Movement of plant nutrients laterally from the organic addition trench into the surrounding subsoil probably contributed to root extension and could be significant in terms of nutrient utilization.

Napropamide Uptake, Transport, and Metabolism in Corn (Zea mays) and Tomato (Lycopersicon esculentum)

Napropamide [2-(α-napthoxy)-N,N-diethylpropionamide] inhibited root and shoot growth in corn (Zea maysL. ‘NC+ 59’) and tomato (Lycopersicon esculentumMill. ‘Niagara VF315’) seedlings. Shoot growth was reduced less than root growth in both species. Corn roots were approximately 10 times more sensitive to napropamide than were tomato roots. Translocation of napropamide from the roots to the shoot of tomato occurred within 0.5 h and followed an apoplastic pattern. Little movement of napropamide from the roots to the shoots occurred in corn. Metabolism of napropamide was not evident in either species during an 8-h exposure. Absorption studies showed that total napropamide levels were 60% higher in corn root tissue than in tomato root tissue. The greater napropamide content in the corn roots was associated with a tightly bound fraction of the total napropamide influx.