Seminal Adventitious Roots Research Articles

Tensile properties of seminal and nodal roots and their relationship with the root diameter and planting density of maize (Zea mays)

The tensile property of roots is an important factor for anchorage and for resistance to root lodging. In this study, a root tensile test was applied to maize (Zea mays L.) grown in the field at three planting densities, 4.5 × 104, 6.75 × 104 and 9.0 × 104 plants ha–1, to quantify the maximum tensile force (Fmax) and tensile strength (Ts) of roots at the V10 stage (tenth leaf visible) and grain-filling stage. In addition, relationships among tensile properties, diameter and turgid weight : dry weight (TW : DW) ratio of roots were investigated. The results showed that the Fmax of primary and seminal adventitious roots was lower than of nodal roots. Among nodal roots, the Fmax of roots on upper nodes was higher. Planting density significantly affected the tensile force of nodal roots of the sixth to eighth tiers; their Fmax decreased with increasing planting density. A positive linear correlation between Fmax and root diameter and a power function between Ts and root diameter was observed. In addition, there was a positive linear correlation between the TW/DW ratio and root diameter and a negative exponential correlation between Ts and TW : DW ratio. Therefore, nodal roots with a lower TW : DW ratio could have a larger Ts, because their cells are smaller and cell walls are thicker. This result suggests that nodal roots with small and thick cells benefit the tensile properties of maize.

Interspecific differences in root architecture among maize and triticale genotypes grown under drought, waterlogging and soil compaction

Environmental stresses (soil compaction, drought, waterlogging) cause changes in plants’ root system structure, also affecting the growth of above-ground parts. The aim of this study was to estimate phenotypic variation among maize and triticale genotypes in root penetration ability through petrolatum-wax-layer (RPA). Also, the effect of shortage or excess of soil water on dry matter of shoots and roots and morphological changes in root system structure in sensitive and resistant maize and triticale genotypes grown in low or high soil compaction level was evaluated. To estimate RPA index, the petrolatum-wax-layer method (PWL) was used. The strength of three petrolatum-wax concentrations 60, 50 and 40 % was 0.52, 1.07 and 1.58 MPa, respectively. High coefficients of variation (CV) were observed in 0.52 and 1.07 MPa and for maize were 19.2 and 21.7 %, and for triticale, 12.5 and 18.3 %, respectively. The data indicate that the use of PWL technique is an effective screening method, and makes it possible to divide the genotypes into resistant and sensitive groups. The second part of this study investigated a multistress effect of soil compaction combined with drought or waterlogging on root and shoot growth and morphological changes in root system structure of maize and triticale genotypes differing in susceptibility to environmental stresses. Seedlings were grown for 4 weeks in root-boxes under conditions of low (LSC 1.1 g cm−3) or severe (SSC 1.6 g cm−3) soil compaction. Drought or waterlogging stresses were applied for 2 weeks from 14th to 28th day. In comparison to LSC treatment, in SSC treatment the decrease in dry matter of shoots and roots was greater for sensitive genotypes of maize and triticale (Ancora, CHD-147). Soil drought or waterlogging caused greater decrease of dry matter of shoots and roots in seedlings grown in SSC in comparison to LSC. The root penetration index (RPI) was estimated as a ratio of root dry matter in 15–40 cm root-box layer to total root dry matter. On the basis of RPI it was possible to group the genotypes according to their ability to distribute roots in soil profile. In comparison to LSC, SSC exerted a strong influence on the length of seminal and seminal adventitious roots, as well as the number and length of L- and S-type lateral roots developed on seminal and nodal roots. In both species the restriction effect of soil compaction on number and length of roots was more severe in sensitive (Ankora, CHD-147) than in resistant (Tina, CHD-247) genotypes. The restriction in roots propagation was greater in triticale than in maize. Exposure to drought or waterlogging in the case of genotypes grown in LSC and SSC treatments caused a decrease in number and length of particular components of root system structure. In both species the decrease of root number and length in plants grown under waterlogging was greater than under drought. The observed changes in root system were greater in sensitive (Ankora, CHD147) than in resistant (Tina, CHD-247) genotypes. Statistically significant correlations were found between RPA and RPI and also between these indexes and soil compaction, drought and waterlogging susceptibility indexes. This indicates that genotypes resistant to soil compaction were resistant to drought or waterlogging and also that genotypes resistant to drought were resistant to waterlogging.

Changes in root system structure, leaf water potential and gas exchange of maize and triticale seedlings affected by soil compaction

The physiological reasons associated with differential sensitivity of C3 and C4 plant species to soil compaction stress are not well explained and understood. The responses of growth characteristics, changes in leaf water potential and gas exchange in maize and triticale to a different soil compaction were investigated. In the present study seedlings of triticale and maize, representative of C3 and C4 plants were subjected to low (L – 1.10gcm−3), moderate (M – 1.34gcm−3) and severe (S – 1.58gcm−3) soil compaction level. Distinct differences in distribution of roots in the soil profile were observed. Plants of treatments M or S in comparison to treatment L, showed a decrease in leaf number, dry mass of stem, leaves and roots, and an increase in the shoot to root ratio. A drastic decrease in root biomass in M and S treatments in the soil profile on depth from 15 to 40cm was observed. Any level of soil compaction did not influence the number of seminal and seminal-adventitious roots but decreased their length. The number and total length of nodal roots decreased with compaction. Changes of growth traits in M and S treatments in comparison to the L were greater for maize than for triticale and were accompanied by daily changes in water potential (ψ) and gas exchange parameters (PN, E, gs). Differences between M and S treatments in daily changes in ψ for maize were in most cases statistically insignificant, whereas for triticale, they were statistically significant. Differences in the responses of maize and triticale to soil compaction were found in PN, E and gs in particular for the measurements taken at 12:00 and 16:00. The highest correlation coefficients were obtained for the relationship between leaf water potential and stomatal conductance, both for maize and triticale, which indicates the close association between stomata behavior and changes in leaf water status.

Impact of soil compaction on root architecture, leaf water status, gas exchange and growth of maize and triticale seedlings

Triticale and maize, with different structure of the root system and type of photosynthesis were examined to know changes in shoot physiology and root architecture in response to varying degree of soil compaction. In the root-box, effects of different levels of soil compaction (1.30, 1.47 and 1.58 Mg m -3 ) on a shoot and root dry matter, leaf number and area, number and length of seminal, seminal adventitious, nodal and lateral roots, leaf water potential (ψ), maximum quantum yield of PS II (Fv/Fm) and gas exchange were studied. Severe soil compaction treatments decreased leaf number, leaf area and dry matter of shoots and roots, while increasing shoot-to-root dry matter ratio. In addition, high level of soil compaction strongly affected the length of seminal and seminal adventitious roots, and the number and length of lateral roots developed on the seminal root. Along with the restriction of root growth, significant influences were observed in ψ, Fv/Fm and gas exchange. High soil compaction treatments resulted in decreased ψ, Fv/Fm, and photosynthetic rate, transpiration rate and stomatal conductance for both triticale and maize. Maize whose root growth was more heavily restricted by the soil compaction compared to triticale showed greater damages in physiological characteristics in leaves, while the impact on triticale was relatively small. The results indicated that damages in photosynthesis, water relation and shoot growth by soil compaction would be closely related to sensitivity of root systems architecture to high mechanical impedance of soil.

Crescimento radicular de plântulas de milho afetado pela resistência do solo à penetração

A resistência do solo à penetração é relacionada com a textura, compactação e umidade do solo. No presente trabalho se estudou o efeito da interação desses fatores sobre o crescimento de raízes de milho. Materiais de solo com 22, 30, 34, 41 e 48% de argila foram acondicionados em tubos de PVC de 10 cm com 4,3 cm de diâmetro interno, nas densidades globais de 1,07, 1,18, 1,36 e 1,53 g cm-3, em três tensões de água: -0,034, -0,106 e -0,640 MPa. Plântulas de milho foram cultivadas nos tubos por 48 horas. Quando a densidade do solo é baixa, a textura tem papel preponderante no crescimento radicular. Esse efeito é menor à medida que aumenta a densidade global. O aumento da resistência do solo à penetração causa diminuição no comprimento e número de raízes seminais adventícias; a raiz seminal primária mostra menor capacidade de penetração do que as raízes seminais adventícias. Resistências do solo à penetração da ordem de 1,3 MPa reduzem à metade o crescimento das raízes seminais adventícias do milho.

Rooting Nodes of Deep Roots in Rice and Maize Grown in a Long Tube

SummaryPenetration of the roots deep into soil layer (deep roots) may alleviate growth inhibition under various soil stress conditions. In this study, the nodes from which deep roots had emerged were examined at the heading stage in rice and maize grown in a 2 m long tube. The effect of soil mechanical stress on the rooting nodes of deep roots was also examined. The roots that emerged in a relatively early growth stage, that is, the roots from coleoptilar, 1st and 2nd node in rice, and the seminal root and roots from the coleoptilar, 1st and 2nd nodes in maize, penetrated into the deep soil layer. The node which produced the highest number of deep roots was the 1st node in rice and the coleoptilar node in maize. Seminal root of rice and seminal adventitious roots of maize did not penetrate into the deep soil layer although they emerged at an early growth stage. In the rice root system, the nodal roots, emerged from the upper portion of the node, tended to penetrate deeper than the nodal roots emerged from the lower portion of the same node. Soil compaction did not affect these tendencies.

Effects of soil compaction on the development of rice and maize root systems

The aim of this study was to determine the effects of soil compaction on the development of root system components of rice ( Oryza sativa L.) and maize ( Zea mays L.). Plants were grown for 4 weeks in root ☐es (24 cm long × 2 cm wide × 40 cm deep) with soil bulk densities of 1.33 g/cm 3 (control) and 1.50 g/cm 3 (compact). In the compact treatment the main root axes of rice never penetrated beyond the 10–15 cm soil layer even by the fourth week, while seminal and seminal adventitious roots of maize had penetrated 30–35 cm deep by the third week. Generally, growth of higher order (second and third) lateral roots compensated for the restricted growth of the main root axes in both species. The ratio of first order L-type laterals producing higher order laterals on their axes was greater in the compact treatment for rice, while that of maize was not significantly increased. The root growth responses of rice and maize to soil compaction were different in the downward penetration of the main axis and the growth of the higher order laterals.

Studies on the Seed of Banana. II. The Anatomy and Morphology of the Seedling of Musa balbisiana

McGahan, Merritt W. (Central Research Labs., United Fruit Co., Norwood, Massachusetts.) Studies on the seed of banana. II. The anatomy and morphology of the seedling of Musa balbisiana. Amer. Jour. Bot. 48(7): 630–637. Illus. 1961.—The first external evidence of germination of the seed of Musa balbisiana is the displacement of the micropylar plug by the elongation of the hypocotyl-radicle axis. As the hypocotyl and epicotyl emerge from the micropylar collar, the seminal adventitious roots become apparent and the cotyledonary sheath surrounding the epicotyl emerges as a coleoptile-like structure. Subsequent growth results in the elongation of the first leaves beyond the cotyledonary sheath and the rapid elongation of the adventitious root system. The vascular transition occurs between the cotyledon and the radicle. The sheath is considered to be only analogous to the coleoptile of the grasses.

STUDIES ON THE SEED OF BANANA. II. THE ANATOMY AND MORPHOLOGY OF THE SEEDLING OF MUSA BALBISIANA

McGahan, Merritt W. (Central Research Labs., United Fruit Co., Norwood, Massachusetts.) Studies on the seed of banana. II. The anatomy and morphology of the seedling of Musa balbisiana. Amer. Jour. Bot. 48(7): 630–637. Illus. 1961.—The first external evidence of germination of the seed of Musa balbisiana is the displacement of the micropylar plug by the elongation of the hypocotyl‐radicle axis. As the hypocotyl and epicotyl emerge from the micropylar collar, the seminal adventitious roots become apparent and the cotyledonary sheath surrounding the epicotyl emerges as a coleoptile‐like structure. Subsequent growth results in the elongation of the first leaves beyond the cotyledonary sheath and the rapid elongation of the adventitious root system. The vascular transition occurs between the cotyledon and the radicle. The sheath is considered to be only analogous to the coleoptile of the grasses.