Agriculture Reference
In-Depth Information
TABLE 5.12
Soil and Plant Mechanisms and Processes and Other Factors Influencing Crop Species/
Genotypic Differences in Nutrient Use Efficiency in Plants
Nutrient Acquisition
Diffusion and mass flow in soil: buffer capacity, ionic concentration and properties, tortuosity, moisture, bulk density,
temperature
Root morphological factors: number, length, extension, density, root hair density
Physiological: root/shoot ratio, root microorganisms (rhizobia, azotobacter, mycorrhizae), nutrient status, water uptake,
nutrient influx and efflux, nutrient transport rates, affinity for uptake (
Km
), threshold concentration (
Cmin
)
Biochemical: enzyme secretion (phosphatases), chelating compounds, phytosiderophores, proton exudates, organic acid
exudates (citric, malic,
trans
-aconitic)
Nutrient Movement in Root
Transfer across endodermal cells and transport in roots
Compartmentalization/binding within roots
Rate of nutrient release to xylem
Nutrient Accumulation and Remobilization in Shoot
Demand at cellular level and storage in vacuoles
Retransport from older to younger leaves and from vegetative to reproductive tissues
Rate of chelation in xylem transport
Nutrient Utilization and Growth
Nutrient metabolism at reduced tissue concentrations
Lower element concentrations in supporting structure, particularly stems
Elemental substitution (Fe for Mn, Mo for P, Co for Ni)
Biochemical: peroxidase for Fe efficiency, ascorbic acid oxidase for Cu, carbonic anhydrase for Zn, metallothionein for
metal toxicities
Other Factors
Soil factors
Soil solution: ionic equilibria, solubility, precipitation, competing ions, organic ions, pH, phytotoxic ions
Physiochemical properties: organic matter, pH, aeration, structure, texture, compaction, moisture
Environmental effects
Intensity and quality of light (solar radiation)
Temperature
Moisture (rainfall, humidity, drought)
Plant diseases, insects, and allelopathy
Source:
Adapted from Baligar, V. C., N. K. Fageria, and Z. L. He. 2001.
Commun. Soil Sci. Plant Anal
. 32:921-950;
Fageria, N. K. and V. C. Baligar. 2003.
J. Plant Nutr
. 26:1315-1333.; Fageria, N. K., V. C. Baligar, and C. A. Jones.
2011.
Growth and Mineral Nutrition of Field Crops
, 3rd edition. Boca Raton, Florida: CRC Press.
parts, retardation of growth and photosynthesis, and increased anthocyanin accumulation (Ono
et al., 1996; Chalker-Scott, 1999; Ding et al., 2005; Diaz et al., 2006).
5.2.8.2 Genetic Mechanisms for Nitrogen Uptake and Assimilation
Nitrogen uptake by plants is mainly in two forms, that is, nitrate (
NO
3
−
) and ammonia (
NH
4
+
).
However, nitrate is the dominant form in most agriculture soils (Fageria, 2014). Nitrate is not only
the predominant source of N supply to plants, but also acts as an important signal for several devel-
opment processes. This regulation includes a rapid change in expression pattern of genes involved
