Term
| the most important factor to the low fertility of acid soil |
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Definition
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Term
this is often the most effective strategy for
improving crop production on acid soils. |
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Definition
| combining the use of Al tolerant cultivars with liming, since the application of lime is often not economically or physically feasible |
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Term
| this is needed for crops to be resistant to Al |
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Definition
To breed genotypes with improved Al
tolerance, reliable, efficient screening
methods must be available to the
researcher. |
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Term
| the pH that constitutes acid soils |
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Definition
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Term
| the amount of the world's ice-free land that has acid soil |
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Definition
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Term
| global distribution of acid soils |
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Definition
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Term
| what most acid soils are found under |
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Definition
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Term
| an example of how parent material can affect soil acidity |
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Definition
| Soils that develop from granite parent materials acidify at a faster rate than soils developed from calcareous parent materials. |
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Term
| why sandy soils acidify more rapidly |
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Definition
| Sandy soils with relatively few clay particles acidify more rapidly due to their smaller reservoir of alkaline cations and higher leaching potential. |
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Term
| some environmental things that acidify soil |
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Definition
| -High rainfall affects the rate of soil acidification depending on the rate of water percolation through the soil profile.
-Organic matter decaying to form carbonic acid and other weak acids also contributes to acidification.
-hydrolyzation of Al
-Net H+ production occurs through natural processes such as nitrification of ammonical nitrogen. |
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Term
| some agricultural things that acidify soil |
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Definition
-Soil acidification is intensified by the removal of cations through the harvesting of crops and by acid precipitation from polluted air.
-Soil acidification is often accelerated by certain cropping practices such as repeated applications of nitrogen in amounts that exceed crop uptake. |
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Term
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Definition
| a material whose Ca and Mg compounds are capable of neutralizing soil acidity |
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Term
| The bulk of agricultural lime comes from... |
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Definition
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Term
| some materials other than lime that are used to neutralize soil acidity |
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Definition
-marl
-slag from iron and steel making
-flue dust from cement plants
-refuse from sugar beet factories, paper mills, calcium carbide plants, rock wool plants, and water softening plants |
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Term
| why it's good to use management practices that optimize N-use efficiency and ultimately reduce the amount of NO3- lost through leaching |
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Definition
| because they could slow the rate of acidification |
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Term
| Acid soils are phytotoxic as a result of... |
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Definition
| nutritional disorders, deficiencies, or unavailability of essential nutrients such as calcium, magnesium, molybdenum, and phosphorus, and toxicity of aluminum, manganese, and hydrogen activity. |
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Term
| this is considered the most important growth-limiting factor for plants in acid soils |
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Definition
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Term
| The primary response to aluminum stress occurs in... |
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Definition
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Term
| description of Al-injured roots |
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Definition
-stubby
-brittle
-Root tips and lateral roots thicken and turn brown.
-The root system as a whole is affected, with many stubby lateral roots and no fine branching.
-Such roots are inefficient in absorbing nutrients and water. |
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Term
| The main symptom of Al toxicity |
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Definition
| rapid inhibition of root growth |
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Term
| the critical site on the root for Al toxicity |
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Definition
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Term
| the part of the corn root that must be exposed to Al to be affected by Al toxicity |
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Definition
| the terminal 2 to 3 mm of the root (root cap and meristem) |
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Term
| does the root cap provide protection against Al damage? |
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Definition
| may or may not, depending on the study |
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Term
| how the root cap may provide protection against Al damage |
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Definition
| through its involvement in signal perception and hormone distribution |
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Term
| types of aluminum tolerance mechanisms |
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Definition
-external tolerance mechanisms
-internal tolerance mechanisms |
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Term
| external tolerance mechanisms |
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Definition
| mechanisms that facilitate Al exclusion from the root apex |
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Term
| internal tolerance mechanisms |
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Definition
| mechanisms that confer the ability to tolerate Al in the plant symplasm |
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Term
| some external tolerance mechanisms by plant roots against Al |
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Definition
1) exudation of organic acids
2) immobilization at the cell wall
3) exudation of phosphate
4) active Al efflux across the plasma membrane
5) production of root mucilage
6) Al exclusion via alterations in rhizosphere pH
7) selective permeability of the plasma membrane |
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Term
| some internal tolerance mechanisms by plant roots against Al |
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Definition
-Al-binding proteins
-chelation in the cytosol
-compartmentation in the vacuole
-evolution of Al tolerant enzymes
-elevated enzyme activity |
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Term
| the only reasonable solution to the problem of acid subsoil |
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Definition
| Selection and development of genotypes with enhanced tolerance to acid soils and toxic levels of Al |
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Term
| some methods for screening for Al tolerance |
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Definition
-cell and tissue culture
-nutrient solution culture
-soil bioassays
-field evaluations
-Laboratory- and greenhouse-based techniques for screening for Al tolerance
-field-based techniques |
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Term
| Nutrient solution culture |
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Definition
| By far the most common screening medium for Al tolerance is solution culture, which provides easy access to the root system, strict control over nutrient availability and pH, and non-destructive measurements of tolerance. |
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Term
| where a plant's primary response to Al stress occurs |
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Definition
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Term
| when soil bioassays have a distinct advantage over nutrient solution culture |
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Definition
| when Al tolerance may be influenced by soil dependent external factors |
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Term
| The ultimate and most direct method of evaluating for Al tolerance |
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Definition
| by measuring economic yield (forage or grain) under field conditions. |
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