Maize Root Development Research Articles

Cellular Dimorphism in the Maize Root Cortex: Involvement of Microtubules, Ethylene and Gibberellin in the Differentiation of Cellular Behaviour in Postmitotic Growth Zones

AbstractDetailed morphometric analysis of cell shapes and an immunofluorescent study of microtubules were carried out on primary roots of Zea mays L. Two types of cells were found to be formed within the postmitotic isodiametric growth (PIG) region of the root cortex that were differentially responsive to low level of exogenous ethylene. The innermost and central cell rows of the cortex were sensitive to ethylene treatment and showed a disturbed distribution of cortical microtubules (CMTs) as well as changed polarity of cell growth, whereas the 2–3 outermost cell rows were less sensitive in this respect. This suggests that post‐mitotic cells of the inner cortex are specific targets for ethylene action. These properties of the inner cortex are compatible with its cells being involved in the formation of aerenchyma; they may also favour root growth in compacted soil. By contrast, the specific properties of the outer cortex indicate that this tissue domain is necessary for the gaseous impermeability and the mechanical strengthening of subjacent aerenchymatous cortex, especially in the mature region of the root.Ethylene affected neither the pattern of cortical cell expansion in the meristem nor the position of the PIG region with respect to the root tip. This contrasts with gibberellin‐deficiency which affected these parameters in both parts of the cortex. These observations indicate a fundamental difference between the role of these two phytohormones in the morphogenesis and development of maize roots.

Temperature effects on nodal root development in maize

Our objective was to determine the effect of temperature on root appearance at successive stalk nodes of a maize (Zea mays L.) plant. Plants were grown in three controlled temperature regimes (30/24, 26/20 and 19/14°C 16-/8-h day/night or 28, 24 and 17.3°C mean), as well as in the field. Three plants were dissected twice a week for morphological observation. A second-degree polynomial, with time as the independent variable and with coefficients linearly related to temperature, was fitted to the controlled-environment data. This equation tested well against two sets of field data. The appearance of newly rooted stalk nodes was related to the appearance of new leaf tips and collars. Such information is urgently needed for predicting leaf, stalk and root growth in maize and other grasses.

Chlorpyrifos and hybrid effects on maize root development in soils reclaimed after surface mining

ABSTRACT The influence of chlorpyrifos and hybrid on corn root characteristics was studied on soils reconstructed after surface mining in southern Illinois. Nodal roots and the number of late metaxylem (LMX) elements from a designated root were counted from mined and undisturbed locations in 1989. Root length density was measured from core segments taken from a reconstructed soil in 1989 and a reconstructed and a nearby undisturbed soil in 1990. Nodal root and LMX counts differed among ten full-season hybrids, but were not affected by chlorpyrifos application on the reconstructed soils. However, total root length in cores was increased 37% in 1989 due to chlorpyrifos, indicating an effect on lateral initiation and/or elongation. Chlorpyrifos promotion of root length was greatest near the surface. Trends suggested hybrids may respond differently to chlorpyrifos application. Improved root elongation may have been due to chlorpyrifos' fungistatic activity. A different set of hybrids did not respond to chlorp...

Maize root development under various levels of salinity and water distribution

An experiment was conducted to study the effect of salinity and water-potential distribution on maize root growth and development. Three salinity distributions and two ranges of soil water potential treatments were prepared by filling 140 cylindrical PVC containers 1.2 m long and 0.25 m in diameter with loamy sand. Root and shoot samples were taken at different growth stages. Saturated electrical conductivity and water content were measured periodically. The results indicated that root and shoot dry-matter accumulation varied significantly among different salinity and water distribution treatments. Root dry-weights continued to increase until flowering stage and then remained constant. No root growth was observed in layers with electrical conductivity > 12 dS/m. For maize root growth under the conditions of this study a salinity level of 12.0 dS/m seemed to be a barrier even under high levels of soil water.

Relation of Verital Root‐Pull Resistance and Flowering in Maize1

Interest in development of maize (Zea mays L.) roots has increased the past 20 years because of the incidence of maize rootworms (Diabrotica species) in the U.S. Corn Belt. Objectives of our study were to determine whether preflower root‐pull resistance was related to postflower root‐pull resistance and whether preflower root‐pull resistance should be included in recurrent selection programs to enhance resistance to root lodging. We evaluated 98 Sj progenies derived from each of four populations at two locations for 3 years for rootpull resistance and at one location for 3 years for frequency of root lodging. The S, progeny heritability estimates for pre‐ (76%) and postflower (81%) root‐pull resistance and root lodging (74%) were relatively high, suggesting that progress could be made for each trait. Genetic correlations between pre‐ and postflower root‐pull resistance ranged from 0.78 to 0.90, but the average genetic correlations between preflower (r = − 0.20) and postflower (r = −0.28) root‐pull resistance and percentage of root lodging were relatively low. Predicted correlated response of postflower root‐pull resistance based on preflower root‐pull resistance was 81.3% (23.9 kg) of predicted direct response (29.4 kg) for postflower root‐pull resistance. Though correlated responses of root‐pull resistance for resistance to root lodging were only 35.5% (postflower) and 25.8% (preflower), greater resistance to root pulling would contribute to reduced root lodging. Our results suggest preflower root‐pull resistance was a good predictor of postflower rootpull resistance and that effective selection can be made at flowering for increased root‐pull resistance.

Influence of within- and between-row mulching on soil temperature, soil moisture, root development and yield of maize (Zea mays L.) in a tropical soil

The effects of zonal mulching on soil physical characteristics and maize (Zea mays) production were investigated for six consecutive maize crops on a tropical Alfisol near Ibadan, Nigeria. Treatments consisted of complete mulch, inter-row mulch, row mulch, and a control. There were differences in soil temperature with respect to mulching, time of the day, and distance from the row. Differences in the maximum soil temperature between mulched and unmulched soil were 3–4°C at 5 cm depth. Soil temperature in the row zone was 2–7°C lower than in the inter-row zone at 15.00 h. Since mulched strips had high earthworm activity, bulk density and penetrometric resistance were low compared with unmulched zones. The mean bulk density of treatments with mulched inter-row was 1.42 and 1.44 gcm−3 compared with 1.50 and 1.64 gcm−3 for treatments with unmulched inter-row, for the 0–10 cm and 10–20 cm depth, respectively. The soil moisture reserve was generally proportional to the area of soil surface covered by mulch. The mean volumetric moisture content in the surface 10 cm of soil was approximately 1.70, 1.58, 1.45, and 1.39 cm for complete mulch, inter-row mulch, row mulch and unmulched control, respectively. The mean and the maximum depth of root penetration were generally greater for treatment with mulched inter-row. In the completely mulched and inter-row mulch treatments, there was a concentration of roots in the surface layer immediately beneath the residue mulch. The inter-row mulch and the completely mulched treatments yielded more than other treatments. Complete mulch yielded 38, 10, and 22% more than the unmulched control in 1973, 1974 and 1975, respectively.

Subsoil gravel horizon and maize root growth

A series of factoral experiments involving the effects of gravel concentration in the subsoil horizon, the effect of inter-gravel bulk density, the depth of the surface soil above the gravel horizon and the interaction between soil moisture regime and gravel concentration, on growth and development of maize roots were conducted in the greenhouse. Increasing sub soil gravel concentration decreased the total porosity and the available waterholding capacity. Though the root growth of maize seedlings was adversely affected by gravel concentration above 20 per cent, lower concentration of gravels had a beneficial effect on roots. The root development and the leaf concentration of N, P and K improved with increasing depth of surface soil above the gravel horizon. The symptoms of mechanical impedance, such as thickening of root tips and profuse branching behind the tip were commonly observed on the root axis penetrating the gravelly horizon. re]19750916