Corn Root Growth Research Articles

The Effect of Nutrient Deficiencies on the Annual Yield and Root Growth of Summer Corn in a Double-Cropping System.

The North China Plain has a typical winter wheat-summer corn double-cropping pattern. The effects of nutrient deficiency conditions on the root characteristics and yield of summer corn in the double-cropping system were studied for four years. Long-term monotonous fertilization patterns undermine crop rotation systems and are detrimental to the sustainability of agricultural production. To complement the development of rational fertilization strategies by exploring the response of crop rotation systems to nutrient deficiencies, an experiment was conducted in a randomized complete block design consisting of five treatments with three replicates for each treatment: (1) an adequate supply of nitrogen and phosphate fertilizers and potash-deficient treatment (T1); (2) an adequate supply of nitrogen and potash fertilizers and phosphorus-deficient treatment (T2); (3) an adequate supply of phosphorus and potash fertilizers and nitrogen-deficient treatment (T3); (4) nutrient-sufficient treatment for crop growth (T4); and (5) no-fertilizer treatment (CK). The results showed that different nutrient treatments had significant effects on the root length density (RLD), root surface area density (RSAD), and root dry weight density (RDWD) in summer corn. At the physiological maturity stage (R6), the root indexes of RLD, RSAD, and RDWD were significantly higher in the 0-20 cm soil layer in T4 compared to CK, with an increase of 86.2%, 131.4%, and 100.0%, respectively. Similarly, in the 20-40 cm soil layer, the root indexes of T4 were 85.7%, 61.3%, and 50.0% higher than CK, with varied differences observed in the other nutrient-deficient treatments. However, there was no significant difference among the treatments in the 40-60 cm layer except for T4, whose root index showed a difference. The root fresh weight and root dry matter in T4, T3, T2, and T1 were increased to different degrees compared with CK. In addition, these differences in root indexes affected the annual yield of crops, which increased by 20.96%, 21.95%, and 8.14% in T4, T2, and T1, respectively, compared to CK. The spike number and the number of grains per spike of T4 were 10.8% and 8.3% higher than those of CK, which led to the differences in summer corn yields. The 1000-kernel weight of T4, T2, and T1 were 9.5%, 8.8%, and 7.4% higher than that of CK, whereas the determining nutrient was nitrogen fertilizer, and phosphorus fertilizer had a higher effect on yield than potassium fertilizer. This provides a theoretical basis for the effect of nutrient deficiency conditions on yield stability in a double-cropping system.

Root exudate-derived compounds stimulate the phosphorus solubilizing ability of bacteria

Low phosphorus (P) availability in soils is a major challenge for sustainable food production, as most soil P is often unavailable for plant uptake and effective strategies to access this P are limited. Certain soil occurring bacteria and root exudate-derived compounds that release P are in combination promising tools to develop applications that increase phosphorus use efficiency in crops. Here, we studied the ability of root exudate compounds (galactinol, threonine, and 4-hydroxybutyric acid) induced under low P conditions to stimulate the ability of bacteria to solubilize P. Galactinol, threonine, and 4-hydroxybutyric acid were incubated with the P solubilizing bacterial strains Enterobacter cloacae, Pseudomonas pseudoalcaligenes, and Bacillus thuringiensis under either inorganic (calcium phosphate) or organic (phytin) forms of plant-unavailable P. Overall, we found that the addition of individual root exudate compounds did not support bacterial growth rates. However, root exudates supplemented to the different bacterial appeared to enhance P solubilizing activity and overall P availability. Threonine and 4-hydroxybutyric acid induced P solubilization in all three bacterial strains. Subsequent exogenous application of threonine to soils improved the root growth of corn, enhanced nitrogen and P concentrations in roots and increased available levels of potassium, calcium and magnesium in soils. Thus, it appears that threonine might promote the bacterial solubilization and plant-uptake of a variety of nutrients. Altogether, these findings expand on the function of exuded specialized compounds and propose alternative approaches to unlock existing phosphorus reservoirs of P in crop lands.

Microbial Solution of Growth-Promoting Bacteria Sprayed on Monoammonium Phosphate for Soybean and Corn Production

Common fertilizers present a low use efficiency caused by nutrient losses (e.g., through leaching, volatilization, adsorption, and precipitation in solution as well as through microbial reduction and immobilization) that create a significant limiting factor in crop production. Inoculation with Plant Growth-Promoting Bacteria (PGPB) is presented as an alternative to increasing fertilizer efficiency. The goal of the study was to test the hypothesis that PGPB (solution with Bacillus subtilis, Bacillus amyloliquefaciens, Bacillus licheniformis, and Bacillus pumilus) can be a strategy to increase the monoammonium phosphate (MAP) efficiency, root growth, and nutrient assimilation of soybean and corn cultivated in arenosol and oxisol. A greenhouse study was developed with the rates of PGPB (rates: 0, 1, 1.33, and 1.66–2.0 L per ton of fertilizer) sprayed on MAP and applied in an arenosol and oxisol cultivated with soybean and corn. Results showed that in both soils and crops, there was a variation in soil biological activity during the experiment. On day 45, PGPB + MAP promoted the beta-glucosidase and ammonium-oxidizing microorganism activities in the arenosol. The PGPB + MAP increased crop root growth in both soils and crops. Plant dry matter was associated with the phosphorous content in the soil, indicating that the phosphorous applied was absorbed by the plants, consequently resulting in a higher accumulation in the plant. Based on the results, the conclusion is that PGPB + MAP increases the growth and phosphorous accumulation of soybean and corn cultivated in the arenosol and oxisol, with a direct effect on crop rooting.

Temperature Effects on the Shoot and Root Growth, Development, and Biomass Accumulation of Corn (Zea mays L.)

Temperature is a critical environmental factor regulating plant growth and yield. Corn is a major agronomic crop produced globally over a vast geographic region, and highly variable climatic conditions occur spatially and temporally throughout these regions. Current literature lacks a comprehensive study comparing the effects of temperature on above versus below-ground growth and development and biomass partitioning of corn measured over time. An experiment was conducted to quantify the impact of temperature on corn’s early vegetative growth and development. Cardinal temperatures (Tmin, Topt, and Tmax) were estimated for different aspects of above- and below-ground growth processes. Plants were subjected to five differing day/night temperature treatments of 20/12, 25/17, 30/22, 35/27, and 40/32 °C using sun-lit controlled environment growth chambers for four weeks post-emergence. Corn plant height, leaves, leaf area, root length, surface area, volume, numbers of tips and forks, and plant component part dry weights were measured weekly. Cardinal temperatures were estimated, and the relationships between parameters and temperature within these cardinal limits were estimated using a modified beta function model. Cardinal temperature limits for whole plant dry weight production were 13.5 °C (Tmin), 30.5 °C (Topt), and 38 °C (Tmax). Biomass resources were prioritized to the root system at low temperatures and leaves at high temperatures. Root growth displayed the lowest optimum temperature compared to root development, shoot growth, and shoot development. The estimated cardinal temperatures and functional algorithms produced in this study, which include both above and below-ground aspects of plant growth, could be helpful to update crop models and could be beneficial to estimate corn growth under varying temperature conditions. These results could also be applicable when considering management decisions for maximizing field production and implementing emerging precision agriculture technology.

Developing Functional Relationships between Soil Waterlogging and Corn Shoot and Root Growth and Development.

Short- and long-term waterlogging conditions impact crop growth and development, preventing crops from reaching their true genetic potential. Two experiments were conducted using a pot-culture facility to better understand soil waterlogging impacts on corn growth and development. Two corn hybrids were grown in 2017 and 2018 under ambient sunlight and temperature conditions. Waterlogging durations of 0, 2, 4, 6, 8, 10, 12, and 14 days were imposed at the V2 growth stage. Morphological (growth and development) and pigment estimation data were collected 15 days after treatments were imposed, 23 days after sowing. As waterlogging was imposed, soil oxygen rapidly decreased until reaching zero in about 8–10 days; upon the termination of the treatments, the oxygen levels recovered to the level of the 0 days treatment within 2 days. Whole-plant dry weight declined as the waterlogging duration increased, and after 2 days of waterlogging, a 44% and 27% decline was observed in experiments 1 and 2, respectively. Leaf area and root volume showed an exponential decay similar to the leaf and root dry weight. Leaf number and plant height were the least sensitive measured parameters and decreased linearly in both experiments. Root forks were the most sensitive parameter after 14 days of waterlogging in both experiments, declining by 83% and 80% in experiments 1 and 2, respectively. The data from this study improve our understanding of how corn plants react to increasing durations of waterlogging. In addition, the functional relationships generated from this study could enhance current corn simulation models for field applications.

Species-dependent response of food crops to polystyrene nanoplastics and microplastics

This study investigated the early responses of four common food crops (Italian lettuce, radish, wheat and corn) by exposing their seeds to suspensions of polystyrene nanoparticles (nano-PS) and microspheres (micro-PS). We found that the crop responses to exposure to nano-PS and micro-PS at different doses were dependent on the plant species. Among the four species, Italian lettuce was the most sensitive crop in terms of seed germination and its germination index after polystyrene exposure for 7 days was inhibited by 18.2%–36.0% compared with that of the control (p < 0.05). The root growth (root dry weight, root/shoot ratio and root length) of Italian lettuce and corn was significantly inhibited by the exposure treatment (p < 0.05), whereas that of radish and wheat was hardly affected. Analyses of antioxidant enzymatic activities, lipid peroxidation, and integrated biomarker indexes confirmed that the toxic effects of nano-PS and micro-PS on crops are likely due to oxidative stress. The observed distribution of fluorescent nano-PS in the roots or germs of the tested crops suggests that nanoplastics can be taken up by plants even at a very early growth stage (<7 days after sowing). Future research is needed in order to obtain more insights into their implications for agricultural sustainability and food safety.

Managing Phosphorus and Potassium Is Key in Conservation Tillage Systems

AbstractMore and more, North American farms are moving toward conservation tillage practices, including no‐till and strip‐till. With this trend has come a lot of questions about how best to apply fertilizers, especially phosphorus and potassium, in conservation tillage. In a recent study, researchers examined how yield and root growth in corn and soybean crops are affected by tillage, fertilizer application rates, and fertilizer placement. The team also looked at nutrient use efficiencies and soil phosphorus and potassium levels. The findings echo the results of previous studies and provide a baseline for best practice recommendations. Earn 0.5 CEUs in Nutrient Management by reading the article and taking the quiz at www.certifiedcropadviser.org/education/classroom/classes/946.

Salinity Stress Effect on the Germination of Three Cereals: Maize (Zea mays), Millet (Pennisetum glaucum) and Rice (Oriza sativa)

In Africa, cereals are major staple foods for the majority of the population. The cereal crop is not immune to the problem of salinity, which could threaten 10% of its world harvest. This work was undertaken to study the comparative effect of salinity on germination of three cereals, maize (Zea mays), millet (Pennisetum glaucum) and rice (Oriza sativa). The seeds were germinated in Petri dishes containing a range of NaCl solution (0 g/l, 5 g/l, 10 g/l, 15 g/l and 25 g/l) in the dark and at room temperature. The harmful effect of salt varies depending on the concentration of NaCl and the type of cereal. It is low on the germination rate of seeds up to a concentration of 10 g/l NaCl. From this dose onwards, this rate is reduced by 44% for millet, 20% for rice and 10% for maize. The average germination time between 0 g/l and 10 g/l NaCl is low and increases strongly between 10 g/l and 15 g/l and reaches 37 days (millet) and 20 days (rice). Corn root growth is less affected by salinity (1.2 cm) at 15 g/l NaCl compared to more sensitive rice and millet (0 cm). The height of the epicotyl between 0 g/l and 25 g/l NaCl increased from 11.8 to 3.6 cm (corn), from 0.5 to 0 cm (rice) and from 4.3 to 0.3 cm (millet). The combination of the parameters studied shows that all three cereals are able to tolerate NaCl concentrations of 10 g/l. Rice is the most sensitive to salinity while maize is more tolerant than millet.

Isolation and characterization of Burkholderia cenocepacia CR318, a phosphate solubilizing bacterium promoting corn growth

Plant-growth promoting rhizobacteria benefit crop health and growth through various mechanisms including phosphate and potassium solubilisation, and antimicrobial activity. Previously, we sequenced the genome of bacterial strain Burkholderia cenocepacia CR318, which was isolated from the roots of the starch corn (Zea mays L.) in London, Ontario, Canada. In this work, the species identity of this isolate is confirmed by recA phylogeny and in silico DNA-DNA hybridization (isDDH), and its plant-growth promoting characteristics are described. B. cenocepacia CR318 exhibited strong activity of inorganic phosphate and potassium solubilization. It significantly promoted the growth of corn plants and roots by solubilizing inorganic tricalcium phosphate under greenhouse conditions. Functional analysis of the complete B. cenocepacia CR318 genome revealed genes associated with phosphate metabolism such as pstSCAB encoding a high affinity inorganic phosphate-specific transporter, and the pqqABCDE gene cluster involved in the biosynthesis of pyrroloquinoline quinone (PQQ), which is a required cofactor for quinoprotein glucose dehydrogenase (Gdh). However, it appears that B. cenocepacia CR318 lacks the quinoprotein Gdh which can produce gluconic acid to solubilize inorganic phosphate. Overall, these findings provide an important step in understanding the molecular mechanisms underlying the plant growth promotion trait of B. cenocepacia CR318.

Cover Crop Rotation Effects on Growth and Development, Seedling Disease, and Yield of Corn and Soybean.

The effects of winter cover crops on root disease and growth of corn and soybeans are poorly understood. A 3-year field experiment investigated the effect of winter cereal rye (Secale cereale L.) and winter camelina (Camelina sativa [L.] Crantz), used either in all three years or in rotation with each other, on corn (Zea mays L.) and soybean (Glycine max. [L.] Merr.) growth, root disease, and yield. Corn following a cover crop of camelina had reduced root disease, a lower Pythium population in seedling roots, and greater growth and yields compared with corn following a rye cover crop. Camelina and rye cover crops before soybean had either a positive or no effect on soybean growth and development, root disease, and yield. Moreover, Pythium clade B populations were greater in corn seedlings after a rye cover crop compared with those following a camelina cover crop, whereas clade F populations were greater on soybean seedlings following a camelina cover crop compared with seedlings following a rye cover crop. A winter camelina cover crop grown before corn had less-negative effects on corn seedling growth, root disease, and final yield than a winter rye cover crop before corn. Neither cover crop had negative effects on soybean, and the cover crop in the preceding spring had no measurable effects on either corn or soybean.

Enhance root-bleeding sap flow and root lodging resistance of maize under a combination of nitrogen strategies and farming practices

A cultivation technique in combination of nutrient strategies has not been implemented on root growth, root-bleeding sap, lodging resistance and production of corn. Therefore, we conducted field trials implementing different cultivation techniques (ridge-furrow system with film covered (RF), ridge-furrow system with soil crust (SC), and flat soil planting system with no ridge and no cover (TF); with four nitrogen levels: 300 kg N ha−1 (3); 200 kg N ha−1 (2); 100 kg N ha−1 (1) and 0 kg N ha−1 (0), during 2015–2016. The aim of this work was to improve soil water storage, yield components, and production through regulating root growth and lodging resistance. The results showed that the RF system under different nutrient levels had significantly improved soil water storage, yield components which led to promote the development of roots in deep soil (0–50 cm) than that of SC and TF planting. The RF2 treatment significantly increased the root volume density (RVD), root weight density (RWD), and root diameter at various growth stages and attained the maximum value at 125 DAP (except root diameter) than that of TF2 treatment. The root surface area density (RSD) and root length density (RLD) were significantly increased in the upper 10–60 cm soil layer under the RF and SC cultivation patterns during silking and maturity stages than that of TF planting under different N levels. However, among the different treatments, there was non-significant variation in RSD and RLD at below 70 cm soil profile. The RF2 and SC2 considerably increased the root dry weight, and the root bleeding sap during entire growth stages of maize crop than that of TF2 planting. The RF system with different N levels delayed roots senescence in the later growth stage, and the production was significantly increased compared with SC and TF planting. Compared with SC2 and TF2 treatment, the RF2 treatment significantly increased the grain yield 5.7 t ha−1 (104%) and reduces root (79%) and stem (95%) lodging rate; therefore, RF2 cultivation method might be an appropriate water saving approach in semi-arid regions.

Genotypic Variation on Root Growth and Nutrient Uptake in Corn and Soybean

Core Ideas Drought‐tolerant corn increased root length up to 33% over conventional corn. Differences in root growth among soybean genotypes were site‐specific. Nutrient dilution effect occurred in both corn shoot and root, but not in soybean. N, P, Mn, and Zn concentrations were higher in the root biomass for soybean compared with corn. Larger root systems can help crops to explore more soil volume and increase nutrient uptake. The objective of this study was to evaluate potential differences in root system growth of two corn (Zea mays L.) and two soybean [Glycine max (L.) Merr.] plants of contrasting genotypes. Two experiments were conducted as part of this study (greenhouse and field). The corn genotypes used in the study were considered as drought tolerant (DT) and conventional (CR)–not drought tolerant; whereas soybean genotypes were considered as highly suitable for poorly drained soils (PD) and suitable for well‐drained soils (GD). During the growing season, shoots and roots biomass were recorded and analyzed for total nutrient concentration. Roots were scanned and processed to measure root length, surface area, diameter, and volume. In the greenhouse, corn root length and volume showed greater values for the DT at the VT growth stage compared with the CR. The DT also showed higher N, Mn, and Zn uptake. In the field, the DT showed greater root length at one location. For soybean, the GD showed increased root surface area and volume at one location when compared with the PD. The PD showed higher Zn uptake than the GD. Furthermore, evaluations of nutrient dilution as a function of root biomass was similar to those observed for shoot biomass for corn, but not clear for soybean. This study emphasizes the importance of root system evaluations among different genotypes as it can help on strategies to increase nutrient uptake by crops.

Consortium of five fungal isolates conditioning root growth and arbuscular mycorrhiza in soybean, corn, and sugarcane.

Plant growth and arbuscular mycorrhizal colonization were studied in sugarcane, corn and soybean by applying five plant growth promoting fungi: Beauveria bassiana, Metarhizium anisopliae, Pochonia chlamydosporia, Purpureocillium lilacinum, and Trichoderma asperella. Sugarcane, corn and soybean were grown in pots under two treatments: (1) inoculation with the fungal consortium and (2) control without inoculation. In the inoculated treatment, fungal spore suspension were applied to the seeds and shoots were sprayed every 28 days. Means were analyzed by analysis of variance and Tukey's test at 5% probability level. The experiment was arranged in a completely randomized design, with six replications. Fungi consortium mediate root growth in soybean and corn, and arbuscular mycorrhizal colonization in soybean and sugarcane. These findings are probably caused by the fungi producing phytohormones and inducing the plants to synthesize phytohormones: auxins for root growth; and jasmonic, abscisic, and salicylic acids with a role in the regulation of mycorrhizal colonization. These effects are important when seeking conservation strategies in agriculture and livestock production, since Fungi consortium can better mediate soil resource acquisition, promoting greater absorption of nutrients and water.

Effect of ZnO nanoparticles on corn seedlings at different temperatures; X-ray absorption spectroscopy and ICP/OES studies

Previous studies have shown that ZnO nanoparticles (NPs) affect corn germination and root growth. However, there is a lack of information about the effects of these NPs at different temperatures. In this study, corn seedlings were exposed to ZnO NPs (24±3nm) at 0–1600mgL−1 and ionic Zn 0–250mgL−1 for 15days. Germination, root elongation, Zn uptake and oxidation state, enzyme activity and protein expression were analyzed. At 20 and 25°C, 400mg ZnO NPs L−1 significantly reduced the germination (40 and 53% respectively), while no effect of Zn2+ was observed. Temperature and Zn concentration affected root growth. At 20°C, ZnO at 50, 400, and 1600mgL−1 reduced root growth by 18, 47, and 26% respectively. At 25°C, 100 and 800mgL−1 increased root growth by 22 and 27%, while at 30°C, 100mgL−1 reduced root growth by 42%. At 30°C, 0.1mgL−1 of Zn2+ increased the growth by 50%. Zn accumulation in seedlings was significant only at 1600mgL−1 ZnO and 250mgL−1 Zn2+. Ascorbate peroxidase activity increased by 24 and 57% under exposure to ZnO at 400 and 1600mgL−1 at 25°C. At any temperature the XAS analyses showed presence on NPs in roots. Exposure to ZnO NPs did not show changes in protein expression; however, a protein band with molecular weight of 85kDa decreased its expression at 30°C, while a protein of 75kDa increased its expression at 30°C. This study suggests that temperature may alter the way the ZnO NPs interact with plants.

Response of corn (Zea mays L.) root growth to soil salinity and compaction under greenhouse conditions

Response of corn (Zea mays L.) root growth to soil salinity and compaction under greenhouse conditions

Optimizing Nitrogen Use Efficiency for No-Till Corn Production by Improving Root Growth and Capturing NO3-N in Subsoil

Subsoil acidity restricts root growth and reduces crop yields in many parts of the world. More than half of the fertilizer nitrogen (N) applied in crop production is currently lost to the environment. This study aimed to investigate the effect of gypsum application on the efficiency of N fertilizer in no-till corn (Zea mays L.) production in southern Brazil. A field experiment examined the effects of surface-applied gypsum (0, 5, 10, and 15 Mg ha−1) and top-dressed ammonium nitrate (NH4NO3) (60, 120, and 180 kg N ha−1) on corn root length, N uptake, and grain yield. A greenhouse experiment was conducted using undisturbed soil columns collected from the field experiment site to evaluate NO3-N leaching, N uptake, and root length with surface-applied gypsum (0 and 10 Mg ha−1) and top-dressed NH4NO3 (0 and 180 kg N ha−1). Amelioration of subsoil acidity due to gypsum application increased corn root growth, N uptake, grain yield, and N use efficiency. Applying gypsum to the soil surface increased corn grain yield by 19%–38% and partial factor productivity of N (PFPN) by 27%–38%, depending on the N application rate. Results of the undisturbed soil column greenhouse experiment showed that improvement of N use efficiency by gypsum application was due to the higher N uptake from NO3-N in the subsoil as a result of increased corn root length. Our results suggest that ameliorating subsoil acidity with gypsum in a no-till corn system could increase N use efficiency, improve grain yield, and reduce environmental risks due to NO3-N leaching.

Root growth, productivity and profitability of baby corn (Zea maysL.) as influenced by nutrition levels under irrigated ecosystem

A field experiment was conducted at Varanasi during the two consecutive prekharif seasons of 2012 and 2013 to work out the optimum levels of NPKS and Zn application for maximizing the productivity and profitability of baby corn under irrigated ecosystem. Results revealed that root parameters, yield and economics of baby corn were influenced significantly by varying the fertility levels. Significantly highest baby cob (9.55 t/ha), baby corn (2.15 t/ha), green fodder yield (31.51 t/ha), gross returns (202.61 × 103 Rs./ha) and net returns (143.40 ×103 Rs./ha) were recorded with the application of 125% RDF. Further, application of 50 kg S/ha resulted in significantly higher baby cob (9.38 t/ha), baby corn (2.15 t/ha), green fodder yield (30.97 t/ha), net profit (142.07 × 103 Rs./ha) over control but it remained at par with application of 25 kg S/ha. Similarly, application of 10 kg Zn/ha gave the maximum baby cob (9.24 t/ha), baby corn (2.10 t/ha) and green fodder yield (30.49 t/ha) with a net profit (138.81×103 Rs./ha) over control but it remained at par with application of 25 kg S/ha. Hence, the application of 125% RDF and 50 kg S/ha along with 10 kg Zn/ha was found optimum to obtain the maximum productivity and profitability of baby corn under irrigated conditions of Varanasi.

Computed tomography scanning can monitor the effects of soil medium on root system development: an example of salt stress in corn.

Seeds and young seedlings often encounter high soluble salt levels in the upmost soil layers, impeding vigorous growth by affecting root establishment. Computed tomography (CT) scanning used at low X-ray doses can help study root development in such conditions non-destructively, because plants are allowed to grow throughout the experiment. Using a high-resolution Toshiba XVision CT scanner, we studied corn (Zea mays L.) root growth under optimal and salt-stressed conditions in 3D and on a weekly basis over 3 weeks. Two groups of three corn plants were grown in the controlled environment of a growth chamber, in mid-sized plastic pots filled with sieved and autoclaved sand. Seedlings were subjected to first CT scanning 1 week after seed planting. Our main research objectives concerning root systems were: (i) to quantify structural complexity from fractal dimensions estimated on skeletal 3-D images built from CT scanning data; (ii) to measure growth from volumes and lengths and the derived relative rates and increments, after isolating primary and secondary roots from the soil medium in CT scanning data; and (iii) to assess differences in complexity and growth per week and over Weeks 1–3 for groups of corn plants. Differences between groups were present from Week 1; starting in Week 2 secondary roots were present and could be isolated, which refined the complexity and growth analyses of root systems. Besides expected Week main effects (P < 0.01 or 0.05), Week × Group interaction (P < 0.05 or 0.10), and Group main effects were observed. Graphical, quantitative, and statistical analyses of CT scanning data were thus completed at an unprecedented level, and provided new and important insights regarding root system development. Repeated CT scanning is the key to a better understanding of the establishment in the soil medium of crop plants such as corn and the assessment of salt stress effects on developing root systems, in complexity, volume, and length.

Phosphate Solubilization by Several Genera of Saprophytic Fungi and Its Influence on Corn and Cowpea Growth

The aim of this study was to test the ability of several strains of fungi, which were isolated from the Brazilian Amazon, to solubilize calcium phosphate in vitro and to promote corn and cowpea growth under axenic conditions. Each plant species received six treatments: inoculation with strains with high solubilization index (SI) (Haematonectria ipomoeae CML 3249 and Pochonia chlamydosporia var. catenulate CML 3250) and control treatments: inoculation with strain that does not solubilize phosphate on Pikovskaya agar (PVK) (Acremonium polychromum FSA115), and non-inoculated treatments with high concentration of insoluble phosphate (HPins), high concentration of soluble phosphate (HPs) or low concentration of soluble phosphate (LPs). The fungi strains had SI between 1.07 cm and 2.03 cm including species without previous report in the literature of their capacity to solubilize calcium phosphate. The two phosphate-solubilizing strains promoted greater corn and cowpea root growth than the controls FSA115, HPins and LPs, to a level similar to the HPs control.

Specific effects of certain salts on the growth of roots of young corn seedlings

The effect of different concentrations of NaCl, Na&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt;, MgCl&lt;sub&gt;2&lt;/sub&gt; and MgSO&lt;sub&gt;4&lt;/sub&gt; on the growth in length of the first seminal root of corn, and on the change in dry weight of the whole seedling and its separate parts have been studied. The effect of mannitol was also investigated for comparison and to study the osmotic effect. The effect of salts on root growth was dependent on the salt species; all effects were specific for the ions investigated, not due to osmotic activity of the solution. The growth of corn roots was suppressed by concentrations of salts much lower than those required to suppress germination. All solutions tested from 1 to 20 meq/l inhibited growth of the root; the retardation increased with increase of concentration. The effect of salts on growth of corn roots was due to both cations and anions and the effect of sodium was stronger than that of magnesium and chloride was more effects than sulphate.