Agriculture Reference
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indole alkaloids were enhanced under NUV light at 4
0
C in
C. roseus
. A homogenate
of
Pythium aphanidermatum
and MJ was studied on
in vitro
cultures of
C. roseus
(cv. 'Dhawal') (Shukla et al.
2010
). Due to elicitation transcriptional upregulation
of strictosidine beta-D:-glucosidase (SGD) occur which in turn improved the syn-
thesis of total alkaloids but did not produce vindoline. Recently in a pot experiment
foliar application of SA was conducted, to find out the unfavorable effects of water
stress on periwinkle and its amelioration by SA (Idrees et al.
2011
). The result sug-
gested that SA (10
−5
M) foliar application minimized destructive effects of stress
and enhanced growth parameters and simultaneously improved the anticancerous
compound VCR and VLB in stressed plants. Aslam et al. (
2011
) reported effects of
freezing and non-freezing temperature on somatic embryogenesis and vinblastine
synthesis in
C. roseus
. At 15ºC temperature maximum numbers of embryos were
produced whereas the same were matured in maximum number at 4ºC. They also
reported that VLB synthesis was temperature dependent. By using cyclodextrins
and methyljasmonate along with a short exposure of UV enhanced the ajmalicine
accumulation in suspension culture of
C. roseus
(Almagro et al.
2011
). In
C. roseus
(Guo et al.
2012
) studied the physiological responses of different nitrogen forms
including varying ratio of nitrate to ammonium (1:0, N
1
; 1:1, N
2
; 1:3 N
3
). After
long term incubation in N
2
nitrogen solution catharanthine and VLB synthesis was
increased to two folds than in N
1
or N
3
nitrogen solution.
Mechanism of Elicitor Action
In order to find out the mechanism of elicitor action in plants a thorough research
has been dedicated (Angelova et al.
2006
; Siddiqui et al.
2010
), however, the in-
duction mechanisms conveyed by fungal elicitors and the plant signals, as a whole,
is still undefined (Djonović et al.
2007
). While understanding the mechanism a
general outline for the biotic elicitation in plants may be abridged by different work-
ers on the basis of elicitor-receptor interaction (Zhao et al.
2005
; Namdeo
2007
).
Elicitors are of very large array of structure, and can be transmitted by the pathogen
(exogenous elicitors) or formed by the plant as a result of the plant-pathogen inter-
action (endogenous elicitors); in both cases, they stimulate the defense reaction of
the plant (Ebel and Cosio
1994
). After pathogen or elicitor recognition, sequences
of cytological variation and biochemical reactions have been identified in plant
cells. The cytological variations include papilla formation, increased cytoplasmic
streaming and nuclear migration, which are connected with depolymerization of
microtubules and microfilaments (Kombrink and Schmelzer
2001
). The biochemi-
cal reactions include transformation in the H
+
, K
+
, Cl
−
, and Ca
2
+
fluxes across
the plasma membrane, and the development of reactive oxygen species (ROS) that
occur within 2-5 min after treatment of elicitor (Low and Merida
1996
; Nürnberger
1999
), oxidative cross linking of cell wall proteins, formation of phytoalexins, hy-
drolytic enzymes, incrustations of cell wall proteins with phenolics and hypersensi-
tive death of plant cell (Namdeo
2007
).
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