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Maize Seedlings (maize + seedling)
Selected AbstractsHumic acids crossinteractions with root and organic acidsANNALS OF APPLIED BIOLOGY, Issue 2 2008L.P. Canellas Abstract The apparent high molecular mass of humic acids (HAs) hardly seems compatible with their direct effects in plant physiology. However, previous evidence has indicated that HAs are non-covalent associations of relatively small molecules, which can be broken down by the action of organic acids. The aim of this work was to evaluate the effects of organic acids on the structure of HAs by spectroscopy and on their bioactivity by following the responses of maize root growth. Changes in the exudation of organic acids from maize seedlings treated with HAs at 50 mg C L,1 were evaluated by high-performance liquid chromatography. The results are in agreement with the concept that HAs are chemical aggregates that acquire characteristics typical of low-molecular-mass humic substances when exposed to organic acids exuded by the roots. Maize seedlings grown in solutions supplemented with HAs plus citric acid at 0.0005, 0.005 and 0.05 mM exhibited significant changes in their root area, primary root length, number of lateral roots and lateral root density and increases in plasma membrane H+ -ATPase activity. Furthermore, the root exudation profile of plants treated with HAs exhibited an increase in the efflux of oxalic and citric acids, with a concurrent decrease in malic and succinic acids. These data reveal a crosstalk between HAs and plants where the exudation of organic acids from the roots influences and is influenced by bioactive molecules released from HAs during root development. [source] The piercing-sucking herbivores Lygus hesperus and Nezara viridula induce volatile emissions in plants ,,ARCHIVES OF INSECT BIOCHEMISTRY AND PHYSIOLOGY (ELECTRONIC), Issue 2 2005Livy Williams III Abstract Plant volatiles induced by herbivory are often used as olfactory cues by foraging herbivores and their natural enemies, and thus have potential for control of agricultural pests. Compared to chewing insects and mites, little is known about plant volatile production following herbivory by insects with piercing-sucking mouthparts. Here, we studied factors (insect life stage, gender, the role of salivary glands, and type of bioassay used for volatile induction) that influence the induction of plant volatiles by two agriculturally important hemipterans, Lygus hesperus and Nezara viridula. Feeding on intact cotton by virgin females of L. hesperus induced 2.6-fold greater volatile response compared to that induced by mated females, possibly due to increased feeding activity by virgin females. This plant volatile response was associated with elicitors present in the insect's salivary glands as well as to the degree of mechanical injury. Feeding injury by N. viridula females also increased volatile emissions in intact maize by approximately 2-fold compared to control plants. Maize seedlings injured by N. viridula emitted higher amounts of the monoterpene linalool, the sesquiterpenes (E)-,-caryophyllene, ,- trans -bergamotene, and (E,E)-,-farnesene, and the homoterpene (E,E)-4,8,12-trimethyl-1,3,7,11-tridecatetraene, but not amounts of green leaf volatiles, compared to uninjured plants. Emissions from intact maize injured by adult males were lower than those emitted by adult females of the same age and did not differ from those emitted by uninjured plants. Similarly, feeding by virgin female N. viridula followed by excision led to 64% higher quantities of volatiles compared to untreated plants. Volatile emission in excised plants, however, was considerably greater than in intact plants, suggesting that careful consideration must be given to bioassay design in studies of herbivore-induced plant volatiles. Salivary gland extracts of N. viridula led to sesquiterpene emissions approximately 2.5-fold higher than for controls, although no significant differences were observed for green leaf volatiles, monoterpenes, and homoterpenes. These results indicate that L. hesperus and female N. viridula feeding induce volatile production in plants, and that volatile production is affected by gender and life stage of the bug. Although oviposition and mechanical injury by stylets may increase release of volatiles, elicitors from salivary glands of L. hesperus and N. viridula also seem to play a role in the emission of plant volatiles. Arch. Insect Biochem. Physiol. 58:84,96, 2005. Published 2005 Wiley-Liss, Inc. [source] Varietal Differences in Development of Maize (Zea mays L.) Seedlings on Compacted SoilsJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 3 2001L. O. Soyelu Differences among open-pollinated tropical maize (Zea mays L.) varieties in seedling development and establishment on compacted soils were studied. Soil dry density was used as an index of compaction. Three soil compaction levels and 12 traits associated with development and establishment of maize seedlings were investigated. A control (without compaction) was also included. Varietal differences were observed for most traits measured. Genetic differences for seedling development on compacted soil were detected. Varietal differences contributed about three times the contribution of compaction to total variability in the traits. Better seedling development and performance were obtained in moderately compacted soil than in the control. Shoot length, shoot dry weight and per cent dry matter in roots were good indicators of the tolerance of maize seedlings to compaction. A physiological strategy for maize seedling establishment on compacted soil was proposed. The implications of the results for seed testing were also highlighted. It was concluded that consideration should be given to the genotype of maize destined for use in ecologies prone to high soil densities. All varieties of maize grown in an agroecological zone could be screened to identify genotypes tolerant of higher soil densities. The seeds could then be multiplied and distributed to farmers. Sortenunterschiede in der Entwicklung von Mais (Zea mays L.)-Sämlingen in verdichteten Böden Sortenunterschiede der Sämlingsentwicklung und des Aufwuchses wurden in verdichteten Böden bei fremdbestäubenden tropischen Mais (Zea mays L.)-Sorten untersucht. Die Bodentrockendichte wurde als Index für die Verdichtung verwendet. Drei Verdichtungsstärken und zwölf Behandlungen im Zusammenhang mit der Entwicklung und dem Anwuchs von Maissämlingen wurden untersucht. Eine Kontrolle (ohne Bodenverdichtung) wurde berücksichtigt. Sortenunterschiede wurden für die meisten Eigenschaften gemessen. Genetische Differenzen der Sämlingsentwicklung in verdichteten Böden konnten beobachtet werden. Sortendifferenzen trugen etwa dreifach im Vergleich zur Bodenverdichtung im Hinblick auf die Gesamtvariabilität der Eigenschaften bei. Bessere Sämlingentwicklung und Sämlingsleistung wurden an moderat verdichteten Böden im Vergleich zur Kontrolle beobachtet. Die Sprosslänge, das Sprosstrockengewicht und die Trockenmasse prozent in Wurzeln gaben gute Hinweise hinsichtlich der Toleranz der Maissämlinge gegenüber Bodenverdichtung. Eine physiologische Strategie für die Maissämlingsentwicklung in verdichteten Böden wird vorgeschlagen. Die Bedeutung der Ergebnisse für Samentestzwecke wurde betont. Es wird angenommen, dass Genotypen für den Anbau in ökologischen Bedingungen, die starke Bodenverdichtungen aufweisen, berücksichtigt werden sollten. Da viele Maissorten in agroökologischen Gebieten angebaut werden, sollten diese getestet werden, um Genotypen mit Toleranz gegenüber stärkerer Bodenverdichtung zu identifizieren. Diese Samen könnten dann vermehrt und an Landwirt abgegeben werden. [source] The Effect of Short Warm Breaks during Chilling on Photosynthesis and the Activity of Antioxidant Enzymes in Plants Sensitive to ChillingJOURNAL OF AGRONOMY AND CROP SCIENCE, Issue 4 2000G. Skrudlik The effect of short warm breaks (from 15 min to 5 h) during chilling of three chilling-sensitive species (tomato, maize and soybean) was investigated. Injuries, intensity of net photosynthesis and antioxidant enzyme activity were measured. Throughout chilling treatment, plants were warmed by transferring them during the last few hours of the light phase from chilling temperature (5 °C for tomato and maize, 2 °C for soybean) to 20 °C. After warming, seedlings were moved back to chilling conditions. Warm breaks of 5 h almost entirely prevented the appearance of injuries, as measured by changes in leakage of electrolytes and tissue water content, during 12 days of chilling. Even a 15-min warm break ensured a significant decrease in injuries in chilled maize seedlings compared to continuously chilled seedlings. Inhibition of gas exchange and fluorescence in seedlings of two maize genotypes differing in chilling resistance was, to a small extent, prevented by 1-h warm breaks, while 4-h warm breaks reduced inhibition significantly. The length of the warm break (1 or 4 h) had no influence on changes in SOD activity compared to continuously chilled plants, but warm breaks of 4 h produced a significant increase in CAT activity. The possible influence of an alternative pathway in preventing injuries is discussed. Zusammenfassung Der Einfluß kurzer warmer Phasen (5 Std. bis 15 Min.) während der Kuühlephase auf drei kühleempfindliche Arten (Tomate, Mais und Sojabohne) wurden untersucht. Schäden, Intensität der Netto-Photosynthese und antioxidierender Enzymaktivität wurden gemessen. Während der Kühlebehandlung wurden die Pflanzen erwärmt, indem sie in den letzten Stunden der Belichtungsphase von den Kühletemperaturen (5 °C für Tomate und Mais, 2 °C für Sojabohnen) unter eine Temperatur von 20 °C verbracht wurden. Nach dem Aufwärmen der Sämlinge wurden sie unter die Kühlebedingungen zurückgebracht. 5 h Wärmeunterbrechungen vermieden nahezu vollständig das Auftreten von Beschädigungen, wie eine Messung der Änderungen im Austritt von Elektrolyten und dem Gewebewassergehalt während der 12 Stunden Kühle zeigten. Selbst 15-Min. Wärmeunterbrechung sicherten eine signifikante Abnahme der Schädigungen von gekühlten Maissämlingen im Vergleich zu ununterbrochen gekühlten Pflanzen. Der Gasaustausch und die Fluoreszensinhibierung von zwei Maisgenotypensämlingen mit unterschiedlicher Kühleresistenz waren in einem geringen Ausmaß vermindert bei 1 h Warmunterbrechung; lediglich 4 h Wärmunterbrechung erwies sich als günstig. Die Länge der Warmunterbrechungen (1 oder 4 h) hatte keinen Einfluß auf Änderungen in der SOD-Aktivität im Vergleich zu kontinuierlich gekühlten Pflanzen; Verlängerungen bis zuf vier Stunden Warmunterbrechungen führten zu einer signifikanten Zunahme der CAT-Aktivität. Eine mögliche Einwirkung alternativer Wege in der Verhinderung von Schäden wird diskutiert. [source] A Novel Mitogen-Activated Protein Kinase Gene in Maize (Zea mays), ZmMPK3, is Involved in Response to Diverse Environmental CuesJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 5 2010Jinxiang Wang In search for components of mitogen-activated protein kinase (MAPK) cascades in maize (Zea mays) involved in response to abscisic acid (ABA) stimulus, a novel MAPK gene, ZmMPK3, from ABA-treated maize leaves cDNA was isolated and characterized. The full length of the ZmMPK3 gene is 1 520 bp and encodes a 376 amino acid protein with a predicted molecular mass of 43.5 kD and a pI of 5.83. ZmMPK3 contains all 11 MAPK conserved subdomains and the phosphorylation motif TEY. Amino acid sequence alignment revealed that ZmMPK3 shared high identity with group-A MAPK in plants. A time course (30,360 min) experiment using a variety of signal molecules and stresses revealed that the transcripts level of ZmMPK3 accumulated markedly and rapidly when maize seedlings were subjected to exogenous signaling molecules: ABA, H2O2, jasmonic acid and salicylic acid, various abiotic stimuli such as cold, drought, ultraviolet light, salinity, heavy metal and mechanical wounding. Its transcription was also found to be tissue-specific regulated. Here, we show that ABA and H2O2 induced a significant increase in the ZmMPK3 activity using immunoprecipitation and in-gel kinase assay. Furthermore, the results showed that the ZmMPK3 protein is localized mainly to the nucleus. These results suggest that the ZmMPK3 may play an important role in response to environmental stresses. [source] Biostimulant activity of two protein hydrolyzates in the growth and nitrogen metabolism of maize seedlingsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2009Andrea Ertani Abstract Two protein hydrolyzate,based fertilizers (PHFs), one from alfalfa (AH) and one from meat flour (MFH), were studied chemically and biologically. AH and MFH revealed a different degree of hydrolysis and a different amino acid composition. The biostimulant activity was investigated using two specific and sensitive bioassays of auxins and gibberellins. Extracts of AH and MFH elicited a gibberellin-like activity and a weak auxin-like one. To improve our understanding of the biostimulant activity, AH and MFH were supplied to maize plants and their effect on growth and nitrate metabolism was studied. Both PHFs increased root and leaf growth and induced morphological changes in root architecture. Besides, the treatments increased nitrate reductase (NR) and glutamine synthetase (GS) activities, suggesting a positive role of the two hydrolyzates in the induction of nitrate conversion into organic nitrogen. Moreover, treatments enhanced GS1 and GS2 isoforms in maize leaves. The latter isoform, amounting to 5- to 7-fold the level of the former, appears to be a superior form in the assimilation of ammonia. The high NR and GS activities together with the high induction of GS isoforms indicate a stimulatory effect of the two PHFs on the assimilation of nitrate. In addition, a role of amino acids and small peptides of the two PHFs is suggested in the regulation of the hormone-like activity and nitrogen pathway. [source] Cytoskeleton-associated, carbohydrate-metabolizing enzymes in maize identified by yeast two-hybrid screeningPHYSIOLOGIA PLANTARUM, Issue 2 2005Daniela Holtgräwe We have used yeast two-hybrid screens and biochemical methods to identify glycolytic enzymes that interact with subcellular structures in hypoxic maize seedlings. As binding domain-bait fusion constructs, we have cloned actin, cytosolic aldolase, the three sucrose synthase (SUS) isoforms SUS1, SUS3, and SH1 as well as the SNF1-related protein kinase into yeast and identified cytosolic isoforms of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), enolase, tubulin, and mitochondrial porin voltage-dependent anion channel protein (VDAC) as well as protein kinases and proteins involved in ubiquitinylation and proteasome-linked degradation as interacting activation domain-prey clones. The results were further confirmed using overlay blots (VDAC) as well as co-polymerization and co-precipitation assays (tubulin and actin). Some results were obtained that support the idea of metabolite and modification effects on the association, namely guanosine triphosphate (GTP)/MgCl2 was necessary for the binding of enolase to actin. GAPDH is inactivated upon association with tubulin but then serves to stabilize the microtubules. The findings support the idea of the dynamic formation of locally associated complexes of enzymes involved in sucrose breakdown and glycolysis in plant cells depending on their metabolic state. [source] Expression of a putative laccase gene, ZmLAC1, in maize primary roots under stress,PLANT CELL & ENVIRONMENT, Issue 5 2006MINGXIANG LIANG ABSTRACT Laccases are multi-copper-containing glycoproteins and comprise a multi-gene family in plants. However, their physiological functions are still not well understood. We obtained sequence information for a putative laccase gene, ZmLAC1, from maize and studied ZmLAC1 expression in detail. The deduced ZmLAC1 protein was 70% identical to LpLAC5-4, a laccase from ryegrass. ZmLAC1 was expressed in leaves, stems and roots of maize seedlings. In unstressed maize primary roots, a higher ZmLAC1 transcript level was located in the basal region where cell elongation had ceased compared to the apical 5 mm of the roots where cells were rapidly dividing and elongating. A treatment with 300 mm NaCl resulted in a shortened root elongation zone (< 2 mm) and swelling in the apical 5 mm. Associated with the morphological change, the transcript level of ZmLAC1 was enhanced in the apical 5 mm, reaching a level similar to that in the basal region. Other abiotic stresses tested , such as 28.5% polyethylene glycol (PEG), which caused an inhibition of root elongation comparable to 300 mm NaCl , did not affect ZmLAC1 transcript level. Potential roles of ZmLAC1 in the roots responding to NaCl or other high concentration of salts are discussed. [source] Humic acids crossinteractions with root and organic acidsANNALS OF APPLIED BIOLOGY, Issue 2 2008L.P. Canellas Abstract The apparent high molecular mass of humic acids (HAs) hardly seems compatible with their direct effects in plant physiology. However, previous evidence has indicated that HAs are non-covalent associations of relatively small molecules, which can be broken down by the action of organic acids. The aim of this work was to evaluate the effects of organic acids on the structure of HAs by spectroscopy and on their bioactivity by following the responses of maize root growth. Changes in the exudation of organic acids from maize seedlings treated with HAs at 50 mg C L,1 were evaluated by high-performance liquid chromatography. The results are in agreement with the concept that HAs are chemical aggregates that acquire characteristics typical of low-molecular-mass humic substances when exposed to organic acids exuded by the roots. Maize seedlings grown in solutions supplemented with HAs plus citric acid at 0.0005, 0.005 and 0.05 mM exhibited significant changes in their root area, primary root length, number of lateral roots and lateral root density and increases in plasma membrane H+ -ATPase activity. Furthermore, the root exudation profile of plants treated with HAs exhibited an increase in the efflux of oxalic and citric acids, with a concurrent decrease in malic and succinic acids. These data reveal a crosstalk between HAs and plants where the exudation of organic acids from the roots influences and is influenced by bioactive molecules released from HAs during root development. [source] | |||||||||||||