0.25%, and 2.0%, respectively, for Zea mays prior to tasselling; 2.8% (N), 0.1% (P),
and, 1.2% (K), for Oryza sativa at tillering stage; 1.75% (N), 0.2% (P), and 1.5%
(K) for Hordeum; 3.2% (N), 0.15% (P), and 2.0% (K) for Sorghum bicolor
(Sahrawat 2006). The sufficiency range also is developmental stage dependent.
This is exemplified by the level of N being 1.75% before heading, and 2.0% at
emergence of head from boot in Triticum aestivum (Sahrawat 2006).
The alteration in root system architecture including change in root length, surface
area, number and density of lateral roots, root mass under nutrient enriched or
nutrient deficient soil has been termed as compensatory response (Russell 1977;
Fageria and Moreira 2011). While discussing alterations in root and root system
architecture in responses to nutrients deficiencies and toxicity, the native RSA of the
plant should be kept in mind. It must also be made clear that the uptake and
assimilation of mineral nutrients are subject to complex interactions, and interdependence as has been demonstrated in several studies (Kellermeier et al. 2014;
Raddatz et al. 2020; Iqbal et al. 2020). Some of the key alterations in root
characteristics under various mineral nutrient stresses are discussed below, and listed
in Table 5.3.
Nitrogen: The availability of Nitrogen is one of the most limiting mineral
nutrients for crop yield. In Zea mays, response of root to N-stress was evaluated in
three genotypes with differing Nitrogen Utilization Efficiency (NitUE). Two of the
three genotypes, B73XLH51 and Arens885855 have high NitUE, whereas Mo17 has
low NitUE. Root dry weight in all genotypes increased under N-deficient (no N )
conditions as compared to when N was available. As the N-availability was
increased, root dry weight decreased for B73XLH51 and Arens885855, the
genotypes with high NitUE, but not significantly for Mo17. Under field conditions,
root length and dry weight reduced as the availability of N was increased; Mo17
showed the most dramatic decrease among the three genotypes (Eghball and
Maranville 1993). In a separate study, root length and root surface area, but not
root diameter of maize, were found to be reduced both under absence of N and high
levels of N (255 kg/ha) as compared to when N was applied at 128 kg/ha (Costa et al.
2002).
In rice, in an early study, effect of N on root architecture was studied on four
different cultivars—Gin-nen, Tamanishiki, Habataki and Norin 25. In all the
cutlivars, similar response of reduced root length and root dry weight was observed
with when N-level was increased from 5 kg/1000 m
2 to 30 kg/1000 m
2 . This was,
however, compensated by increase in number of nodal roots (Tanaka et al. 1995).
Similar response of reduced root length and root dry weight upon increase in Napplication has also been observed in other rice cultivars (Fageira and Moreira
2011). Ogawa et al. (2014), however, observed variation when cultivars of
O. sativa and several other species of rice, namely O. barthii, O. glaberrima, and
O. rufipogon derived from different ecosystems were subjected to different
concentrations of N (0, 50, and 500 μMd). Majority of the cultivars showed a
continuous declining trend in root length from 0, 50, and 500 μM, whereas a few
cultivars showed increased root length from 0 to 50 μM and then decrease in length
from 50 to 500 μM concentration (Ogawa et al. 2014). However, all cultivars
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E. Bhardwaj et al.
and, 1.2% (K), for Oryza sativa at tillering stage; 1.75% (N), 0.2% (P), and 1.5%
(K) for Hordeum; 3.2% (N), 0.15% (P), and 2.0% (K) for Sorghum bicolor
(Sahrawat 2006). The sufficiency range also is developmental stage dependent.
This is exemplified by the level of N being 1.75% before heading, and 2.0% at
emergence of head from boot in Triticum aestivum (Sahrawat 2006).
The alteration in root system architecture including change in root length, surface
area, number and density of lateral roots, root mass under nutrient enriched or
nutrient deficient soil has been termed as compensatory response (Russell 1977;
Fageria and Moreira 2011). While discussing alterations in root and root system
architecture in responses to nutrients deficiencies and toxicity, the native RSA of the
plant should be kept in mind. It must also be made clear that the uptake and
assimilation of mineral nutrients are subject to complex interactions, and interdependence as has been demonstrated in several studies (Kellermeier et al. 2014;
Raddatz et al. 2020; Iqbal et al. 2020). Some of the key alterations in root
characteristics under various mineral nutrient stresses are discussed below, and listed
in Table 5.3.
Nitrogen: The availability of Nitrogen is one of the most limiting mineral
nutrients for crop yield. In Zea mays, response of root to N-stress was evaluated in
three genotypes with differing Nitrogen Utilization Efficiency (NitUE). Two of the
three genotypes, B73XLH51 and Arens885855 have high NitUE, whereas Mo17 has
low NitUE. Root dry weight in all genotypes increased under N-deficient (no N )
conditions as compared to when N was available. As the N-availability was
increased, root dry weight decreased for B73XLH51 and Arens885855, the
genotypes with high NitUE, but not significantly for Mo17. Under field conditions,
root length and dry weight reduced as the availability of N was increased; Mo17
showed the most dramatic decrease among the three genotypes (Eghball and
Maranville 1993). In a separate study, root length and root surface area, but not
root diameter of maize, were found to be reduced both under absence of N and high
levels of N (255 kg/ha) as compared to when N was applied at 128 kg/ha (Costa et al.
2002).
In rice, in an early study, effect of N on root architecture was studied on four
different cultivars—Gin-nen, Tamanishiki, Habataki and Norin 25. In all the
cutlivars, similar response of reduced root length and root dry weight was observed
with when N-level was increased from 5 kg/1000 m
2 to 30 kg/1000 m
2 . This was,
however, compensated by increase in number of nodal roots (Tanaka et al. 1995).
Similar response of reduced root length and root dry weight upon increase in Napplication has also been observed in other rice cultivars (Fageira and Moreira
2011). Ogawa et al. (2014), however, observed variation when cultivars of
O. sativa and several other species of rice, namely O. barthii, O. glaberrima, and
O. rufipogon derived from different ecosystems were subjected to different
concentrations of N (0, 50, and 500 μMd). Majority of the cultivars showed a
continuous declining trend in root length from 0, 50, and 500 μM, whereas a few
cultivars showed increased root length from 0 to 50 μM and then decrease in length
from 50 to 500 μM concentration (Ogawa et al. 2014). However, all cultivars
140
E. Bhardwaj et al.