Root Lignin Research Articles

Manganese nutrition and accumulation of phenolics and lignin as related to differential resistance of wheat genotypes to the take-all fungus

Differential resistance of four Triticum aestivum L. genotypes to isolates of take-all fungus (Gaeuman-nomyces graminis var. ritici Walker) was tested in a complete factorial experiment set up in a growth chamber using Mn-deficient Wangary sand amended with four rates of Mn. Mn-efficient cultivars produced more dry matter at low supply of Mn. Fertilization with Mn significantly increased its accumulation in roots and shoots. The most sensitive measure of take-all infection was the total length of root stellar lesions; these lesions were reduced by Mn fertilization and were shorter in Mn-efficient genotypes. The resistance-enhancing effect of Mn was the most obvious in the Mn-inefficient genotype (Bayonet) and the least obvious in the Mn-efficient one (C8MM). Phenolics biosynthesis in roots was clicited by fungal infection, especially in the case of the highly virulent isolate. The weakly virulent isolate increased phenolics concentration in roots much more if no Mn was added, indicating that the resistance-enhancing effect of Mn may not be directly exerted through the effects on phenolics biosynthesis. Lignin concentration in roots decreased due to Mn fertilization, while no effect of take-all infection was noted. It appears that biosynthesis of phenolics and lignin in wheat roots has a low Mn requirement which can be satisfied at environmental Mn concentrations below those necessary for optimum plant growth. ei]Section editor: A C Borstlap ei]Section editor: H Lambers

Seasonal Patterns Associated withTylenchulus semipenetransandPhytophthora parasiticain the Citrus Rhizosphere

Populations of Tylenchulus semipenetrans and Phytophthora parasitica were measured weekly during 27 mo in an orchard of mature grapefruit trees on rough lemon rootstock in the central ridge region of Florida. The study was conducted to identify potential key climatic and host factors affecting population changes in both parasites. Patterns of change in root mass density and concentrations of root lignin and nonstructural carbohydrate suggested annual as well as seasonal variation in the age structure and nutritional value of the fibrous root system. Numbers of nematode females on roots and juveniles and males in soil were related positively (P=0.01) to root mass density and root concentration of reducing sugars, starch, and total nonstructural carbohydrates [...]

Influence of near-ultraviolet light enhancement and photosynthetic photon flux density during photoperiod extension on the morphology and lignin content of black spruce seedlings

When containerized black spruce seedlings (Picea mariana (Mill.) B.S.P.) are grown rapidly in greenhouse culture, they sometimes bend over, grow horizontally and become deformed. This phenomenon has been known to affect between 5% and 10% of a winter greenhouse crop. In this study, near-ultraviolet lamps were used to supplement the artificial light received from high-pressure sodium lamps and the effects on seedling morphology and lignin contents were examined. Neither height to diameter ratios nor lignin concentrations were significantly affected by UV radiation flux density. However, seedling biomass, height, root collar diameter, lignin content, and lignin to cellulose ratios of stems were significantly correlated with total photosynthetic photon flux density (PPFD) received during photoperiod extension. Height to diameter ratios were negatively correlated with PPFD during photoperiod enhancement because of a greater relative increase in diameter growth compared with height growth. Neither UV nor PAR flux density affected the percentage of black spruce seedlings having stem deformations greater than 30 ° from the vertical.

The influence of metal halide and high-pressure sodium lamps during photoperiod extension on the allocation of carbon between lignin and cellulose in black spruce seedlings

Containerized black spruce seedlings (Piceamariana (Mill.) B.S.P.) were grown at the greenhouse at CIP Inc., Harrington, Québec, from February until May, 1987. We wished to test whether differences in the quantity and quality of light received from two commercially available lamps during photoperiod extension would alter the allocation of carbon between lignin and cellulose in shoots and roots. Photoperiods were extended from 17:00 to 01:00 using either metal halide and high-pressure sodium lamps together or high-pressure sodium lamps alone. At night, the treatment using both types of lamp together increased the photon flux density of blue light (400–500 nm) at seedling height 10-fold, from 0.32 to 3.2 μE m−2 s−1. Photosynthetically active radiation was increased 4-fold, from 4.5 to 17.9 μE m−2 s−1. Total seedling biomass did not differ statistically between light treatments at any given time. However, seedling biomass averaged over all times was statistically higher (p ≤ 0.03) for seedlings in the treatment using both types of lamp together. Percent lignin, percent cellulose, and lignin to cellulose ratios were not significantly affected by the light source used during photoperiod extension. As expected, percent lignin and percent cellulose in shoots and roots increased significantly with time. The percentage of seedlings judged unacceptable because of spiralized stems was not affected by light source and averaged 21.9%.

Soil Organic Matter: II. Studies of the Origin and Chemical Structure of Soil Humic Acids

AbstractSmall quantities of soil humic acids were supplied to cultures of Nostoc muscorum, resulting in stimulation of growth and nitrogen fixation. Various organic compounds were added to compare stimulations and structural relationships. Of all the compounds tested, catechol and humic acids were found to give the greatest increases of nitrogen fixed. Part of the increase in nitrogen fixation was thought to be due to boron contained by the humic acids. Lignin oxidized by H2O2 and microorganisms was analyzed by infrared spectroscopy. The product formed by microorganisms gave a material with similar paper electrophoretic mobility as natural humic acids. Controlled degradation of humic acids and lignin gave various phenols. Humic acid chromatograms showed four phenols present: catechol, phenol, guaiacol, and o‐cresol. One spot found in the humic acid chromatograms has not yet been identified. Bean root lignin when subjected to the same degradation gave a spot in the same position and with the same color. Guaiacol and phenol were also identified from bean root lignin.