Agriculture Reference
In-Depth Information
14.3.2 WATER STRESS
Under drought stress conditions, the extension of root surface by the extr-
aradical mycelia of AM fungi enhances the acquisition of water and nutri-
ents. It has been demonstrated that AMF colonized plants in field are better
adapted and attributed this response to reduced water stress. Mycorrhizae
improves water uptake by exploring the soil volume, improving plant nu-
trition, and/or regulating stomata through hormone synthesis. It has been
shown that phosphorus levels, tissue dry weight and transpiration of AM
seedlings were greater than noninoculated citrus plants. It is attributed that
improved establishment of citrus to drought conditions was mainly due to
improved P uptake and reduced plant stress. On the contrary, it has been
observed that low transpiration rate and higher water use efficiency in my-
corrhizal
ber
seedlings due to increased stomatal resistance provided by
the AM colonization under arid and semiarid conditions. Mycorrhizal root
colonization may indirectly influence the stomatal behavior of host leaves
and higher in mycorrhizal than nonmycorrhizal plants. The stomatal con-
ductance and leaf water potential are also altered (Auge et al., 1986, 1987,
2001). This effect was attributed to more efficient extraction of soil mois-
ture by mycorrhizal root systems in drought conditions. Furthermore, it
has been observed that there is enhanced nitrate reductase activity in roots
and leaves of AM infected plants due to improved P nutrition. Some of the
role of AMF symbiosis in fruit crops is mentioned hereunder (Table 14.3).
TABLE 14.3
AMF in Mitigation of Low Moisture and Drought Conditions
Crop
AMF + bioagent
Beneficial effect
Reference
Grape 'Cabernet Sau-
vignon'
Mixed AMF
Drought stress
Schreiner et al.
(2007)
Grape 'Pinot Noir'
Mixed AMF
Root spread, higher
Mg and Zn uptake and
moisture stress
Schreiner (2005)
Carrizo citrange
Glomus intrara-
dices
Drought and trans-
plant stress
Johnson and
Hummel (1985)
Sour orange and Car-
rizo citrange
-do-
Drought and enhanced
growth
Dutra et al.
(1996)
