Agriculture Reference
In-Depth Information
differential biochemical responses of the salt-sensitive (IR-29), salt-tolerant (Pok-
kali) and aromatic (Pusa Basmati or PB) rice varieties during polyethylene glycol
(PEG)-induced dehydration stress. They found that drought resistant cultivars had
higher free Spd and free Spm in the leaves than drought-susceptible ones during the
whole period of withholding of water. Moreover, stressed Pokkali rice plants ap-
peared to suffer lesser damage, parallely with the maximum accumulation level of
the higher PAs - Spd and Spm. The authors also reported that water stress increased
the activities of arginine decarboxylase, SAMDC, and Spd synthase in the leaves,
in consonance with rise observed in leaf Put, Spd, and Spm.
The effect of drought stress has also been studied in several non-gramineous
species. In 15-day-old chickpea (
Cicer arietinum
) seedlings, fast rise in Spd and
Spm levels was observed after exposure to osmotic stress created by incorporating
polyethylene glycol - 6000 (PEG) in the growth medium for four days (Nayyar and
Chander
2004
). Vetiver grass (
Vetiveria zizanioides
) is considered to have future
potential as bio-fuel for power generation and cellulosic ethanol (Paul et al.
2008
).
Zhou and Yu (
2010
) studied the variations of PAs contents in plants of this species
when stressed with 20, 40, and 60 % PEG solutions for six days. Their results showed
that under osmotic stress, free and conjugated Put decreased, whereas free and con-
jugated Spd and Spm amounts increased. Lei (
2008
) used
Populus przewalskii
as a
tree model species to investigate the acclimation and adaptation to drought stress,
in particular the ROS damaging effects and their scavenging systems.
P. przewalskii
plants subjected to water withholding showed reduced biomass accumulation, shoot
height and basal diameter. Drought stress also increased Put and Spd, while little
change was observed in the Spm level (Lei
2008
). Cacao (
Theobroma cacao
) plants
subjected to 10 days of drought showed augmented Put, Spd and Spm in leaves
(Bae et al.
2008
). Also, a correlation was found between enhanced expression of
TcODC and TcSAMDC with changes in leaf water potential. These expressions
were preceded by induction at seven days of TcADC and TcSAMDC in roots. In
leaves of this species, TcSPDS and TcSPMS were not responsive to drought, but the
expressions of these genes were slightly upregulated in drought-stressed roots. The
authors speculated that since PAs are associated with root development, it is pos-
sible that the induction of PA biosynthesis genes in roots were involved in shifting
the root architecture of cacao plants in response to stress, as it was suggested in the
subantartic cruciferous species
Pringlea antiscorbutica
(Hummel et al.
2002
). PAs
involvement in the development and ripening of fruit emerges from variations ob-
served in their levels in several fruit crops (Serrano et al.
1995
; Ponappa and Miller
1996
; Geny et al.
1999
; Shiozaki et al.
2000
). Antolín et al. (
2008
) investigated how
the balances of PAs were affected by drought in grapevine (
Vitis vinifera
). The PAs
level was analyzed at distinct stages of berry ripening: onset of veraison, middle
veraison and harvest. Their data showed that at the onset of veraison, concentra-
tions of berry PAs were higher in both deficit irrigation treatments than in control
grapevines, although those differences disappeared during ripening. Possibly, PAs
contribute to increased fruit growth rate (Baigorri et al.
2001
; Shiozaki et al.
2000
).
Also in grapevine, total PAs were significantly lower in the control tolerant and
higher in the control sensitive genotype (Toumi et al.
2010
), and these titers respec-
