Publisher Summary This chapter illustrates the developments in the field of aeration since 1960, which have culminated in the modeling of the oxygen movements within the plant. The chapter collates the mathematical approaches to the aeration process and explains the concepts of modeling in a simplified manner. It is noted that the environment exerts a considerable influence on the directional flow of the respiratory gases within the plant and the directional exchange with the atmosphere. Oxygen can enter the plant body in a variety of ways. In non-aquatic species, the stomata and lenticels provide paths of low resistance for the entry and exit of both oxygen and carbon dioxide. In submerged astomatal aquatics, surface permeabilities are sufficiently high to allow the necessary gas transference. Plants rooted in unsaturated soils are exposed to an oxygen-rich environment over the greater part of their shoot and root surfaces. Oxygen enters the plant in the combined state as water. As water, it is transported from root to shoot in the xylem where a proportion is finally released into the liquid phase within the chloroplasts during the photolysis stage of photosynthesis.

Aeration in Higher Plants

This paper presents a critical review on nitrogen (N) transformations functioning in flooded soils and sediments, and their role in N loss from the system. Nitrogen transformations reviewed include (1) ammonification (organic ? ammonium N) (2) nitrification (ammonium ? nitrate), (3) ammonia volatilization (ammonium N ? NH3), (4) denitrification (nitrate ? gaseous products N2O and N2). Transport processes reviewed were ammonium and nitrate diffusion. Inorganic N in flooded soils and sediments and waters is converted to gaseous forms by two processes, i.e., (1) nitrification‐denitrification; and (2) NH3 volatilization. The former process seems to be more predominantly involved in the ammonium N loss from the sediments, whereas the latter process occurs under specialized conditions, mainly in the overlying waters. The processes involved in converting organic N to gaseous end products include ammonification of organic N to ammonium N, upward diffusion of ammonium N into the aerobic soil layer, oxidation of am...

Nitrogen transformations and loss in flooded soils and sediments

Measuring plant-associated nitrogen fixation in agricultural systems

Publisher Summary Crop residues, usually considered a problem, when managed correctly can improve soil organic matter dynamics and nutrient cycling, thereby creating a rather favorable environment for plant growth. The intelligent management and utilization of crop residues is essential for the improvement of soil quality and crop productivity under rice-based cropping systems of the tropics. Viable option is to retain residue in the field; burning should be avoided. The major issue is adapting drills to sow into loose residues. Strategies include chopping and spreading of straw during or after combining or the use of disc-type trash drills. Residues rich in lignin and polyphenol contents experience the lowest decay. Decomposition of crop residues occurs at a rapid rate—about 80% of crop residue C is lost in the first year—under the warm and humid conditions of the tropics. Factors that control C decomposition also affect the N mineralization from the crop residues. Decomposition of poor-quality residues with low N contents, high C:N ratios, and high lignin and polyphenol contents generally results in microbial immobilization of soil and fertilizer N. Nutrient cycling in the soil–plant ecosystem is an essential component of sustainable productive agricultural enterprise. Although during the last three decades, fertilization practices have played a dominant role in the rice-based cropping systems, crop residues—the harvest remnants of the previous crop still play an essential role in the cycling of nutrients. Incorporation of crop residues alters the soil environment that in turn influences the microbial population and activity in the soil and subsequent nutrient transformations.

Crop residue management for nutrient cycling and improving soil productivity in rice-based cropping systems in the tropics

In response to the colonization by arbuscular mycorrhizal (AM) fungi, plants reprioritize their phosphate (Pi)-uptake strategies to take advantage of nutrient transfer via the fungus. The mechanisms underlying Pi transport are beginning to be understood, and recently, details of the regulation of plant and fungal Pi transporters in the AM symbiosis have been revealed. This review summarizes recent advances in this area and explores current data and hypotheses of how the plant Pi status affects the symbiosis. Finally, suggestions of an interrelationship of Pi and nitrogen (N) in the AM symbiosis are discussed.

https://www.onlinelibrary.wiley.com/doi/pdf/10.1111/j.1365-3040.2006.01617.x

Phosphate in the arbuscular mycorrhizal symbiosis: transport properties and regulatory roles

The organic acids, formic, acetic, propionic, and butyric acids when applied at 0.5 and at 1.0 mmole/100 g soil to neutral Philippine soils, retarded rice growth. Acids with higher molecular weight had more distinct retarding effects. Soil with fresh green manure temporarily produced fairly high amounts of acetic, propionic, and butyric acid, and in submerged soils they occurred within 2 weeks. Acetic acid was the major organic acid produced. The cause of the retardation of rice plant in the soil amended with green manure was considered to be due to the organic acids produced in the soil. The growth retardation of rice plant was prevented by the addition of ammonium sulfate but not by the addition of ammonium chloride. We found much less propionic and butyric acid in the soils with ammonium sulfate.

https://www.tandfonline.com/doi/pdf/10.1080/00380768.1973.10432517

Effect of organic acid transformations in submerged soils on growth of the rice plant

The localization of acid and alkaline phosphatases in the intraradical hyphae of the arbuscular mycorrhizal fungi, Glomus mosseae (Nicol. and Gerd.) Gerd. and Trappe (Gm), Gl. etunicatum Becker and Gerd. (Ge) and Gigaspora rosea Nicol. and Schenck (Gir) were compared. Marigold (Tagetes patula L.) and leek (Allium porrum L.) were inoculated with each of the three fungi. The mycorrhizal roots were harvested at 3, 4, 5 and 6 weeks after sowing (WAS), treated with a digestion solution containing cellulase and pectinase, and then stained for phosphatase activities at pH 5.0 and pH 8.5. The development of fungal structures in the host root was also examined. Gm formed fine-branched (mature) arbuscules only at the early phase of infection (3 to 4 WAS). Mature arbuscules of Ge and Gir were observed from the early phase (4 WAS) up to the end of experiment. At pH 5.0, the localization of the phosphatase activities of the three fungi were similar irrespective to host plant species. The activity appeared in mature arbuscules and intercellular hyphae, whereas the collapsed arbuscules were inactive. Ten millimolar NaF, an acid phosphatase inhibitor, inhibited the phosphatase activities of Gm and Ge but did not affect that of Gir. At pH 8.5, a difference among the fungal species was found in the localization of phosphatase activity while that between host species was not. The mature arbuscules were also the active sites in all three species. Only Gir showed the activity in the intercellular hyphae while the two Glomus spp. did not. Five millimolar EDTA inhibited the activity of Gir at pH 8.5 while the activities of Ge and Gm were not affected by either 5 mM EDTA or 10 mM KCN (both are alkaline phosphatase inhibitors).

Comparison of phosphatase localization in the intraradical hyphae of arbuscular mycorrhizal fungi, Glomus spp. and Gigaspora spp.

Specific inhibitor and substrate specificity of alkaline phosphatase in the arbuscule of Glomus etunicatum were investigated, and the possible role of this enzyme in the symbiosis was discussed. Mycor­ rhizal roots of marigold (Tagetes patula) were digest­ ed by cellulase and pectinase to separate the intrarad­ ical hyphae from the root tissue, and phosphatase activity was stained at pH 8.5 and 5.0. The activity.of alkaline phosphatase (pH 8.5) in arbuscules was m­ hibited in the presence of beryllium, whereas that of acid phosphatase (pH 5.0) was less sensitive to beryl­ lium. Specificity and effectiveness of beryllium on the alkaline phosphatase was further confirmed using fractionated (soluble and insoluble) enzyme pre­ pared from the separated hyphae. The soluble and insoluble alkaline phosphatases hydrolyzed phospho­ monoester compounds (glucose-6-phosphate, l3-glyc­ erophosphate, trehalose-6-phosphate and glucose 1- phosphate) but not pyrophosphate compounds (A-:r:P and polyphosphate) which were hydrolyzed by aCId phosphatase efficiently. The insoluble alkaline ph~s­ phatase showed high specific activity (on a protem basis) and high sensitivity to beryllium. Kinetic anal­ ysis of the insoluble alkaline phosphatase suggested the involvement of this enzyme in the sugar metab­ olism of the fungus due to lower Km values for sugar phosphate such as glucose-6-phosphate and treha­ lose-6-phosphate.

/pdf/specific-inhibitor-and-substrate-specificity-of-alkaline-2ucm4ghh73.pdf

Specific inhibitor and substrate specificity of alkaline phosphatase expressed in the symbiotic phase of the arbuscular mycorrhizal fungus, Glomus etunicatum

Specific inhibitor and substrate specificity of alkaline phosphatase in the arbuscule of Glomus etunicatum were investigated, and the possible role of this enzyme in the symbiosis was discussed. Mycor- rhizal roots of marigold (Tagetes patula) were digest- ed by cellulase and pectinase to separate the intrarad- ical hyphae from the root tissue, and phosphatase activity was stained at pH 8.5 and 5.0. The activity of alkaline phosphatase (pH 8.5) in arbuscules was in- hibited in the presence of beryllium, whereas that of acid phosphatase (pH 5.0) was less sensitive to beryl- lium. Specificity and effectiveness of beryllium on the alkaline phosphatase was further confirmed using fractionated (soluble and insoluble) enzyme pre- pared from the separated hyphae. The soluble and insoluble alkaline phosphatases hydrolyzed phospho- monoester compounds (glucose-6-phosphate, (3-glyc- erophosphate, trehalose-6-phosphate and glucose 1- phosphate) but not pyrophosphate compounds (ATP and polyphosphate) which were hydrolyzed by acid phosphatase efficiently. The insoluble alkaline phos- phatase showed high specific activity (on a protein basis) and high sensitivity to beryllium. Kinetic anal- ysis of the insoluble alkaline phosphatase suggested the involvement of this enzyme in the sugar metab- olism of the fungus due to lower Km values for sugar phosphate such as glucose-6-phosphate and treha-

Specific inhibitor and substrate specificity of alkaline phosphatase expressed in the symbiotic phase of the arbuscular mycorrhizal fungus

The phosphatase specific to the infection of vesicular-arbuscular mycorrhizal fungi (Glomus etunicatum Becker & Gerdemann) in marigold (Tagetes patula L.) roots was investigated in relation to the mycorrhizal growth promotion in host plant. Mycorrhizal and non-mycorrhizal marigold plants were cultured in a growth chamber, and the enzyme solution was extracted from 2- to 10-week-old plant roots. The infection-specific phosphatase (ISPase) was detected in the mycorrhizal root extract from the beginning of the infection (4-week-old plant) by an electrophoretical technique. The activity increased as the infection rate increased, and decreased at the stationary phase of the host growth when the infection rate was still high. The effect of phosphorus (P) fertilization on the ISPase activity and the mycorrhizal growth promotion in host was investigated in 4- to 8-week-old plants using two kinds of liquid fertilizers with different P concentrations. The plants without P-fertilization showed more increase...

Tomio Yoshida

Papers

Effect of organic acid transformations in submerged soils on growth of the rice plant

Comparison of phosphatase localization in the intraradical hyphae of arbuscular mycorrhizal fungi, Glomus spp. and Gigaspora spp.

Specific inhibitor and substrate specificity of alkaline phosphatase expressed in the symbiotic phase of the arbuscular mycorrhizal fungus, Glomus etunicatum

Specific inhibitor and substrate specificity of alkaline phosphatase expressed in the symbiotic phase of the arbuscular mycorrhizal fungus

Characterization of phosphatase in marigold roots infected with vesicular-arbuscular mycorrhizal fungi