Agriculture Reference
In-Depth Information
case of roses,
Rosa indica
(var Odorata) has the abilities to withstand high
levels of pH an indication of excessive soil salinity. Such species can be
included in the breeding program to transfer the genes of interest. Similar-
ly resistance to high level of salts is found in carnations species
Dianthus
aydogduii
which can be incorporated in the breeding program.
13.5.6.2
BIOTECH APPROACHES
The reduced ability of the plant to take up water induces water deficit
effects comparable to drought stress. It is therefore not surprising to find
similarities in the signaling and response of drought and salt stressed
plants. This includes ABA biosynthesis and accumulation, which regulate
measures against water loss such as closure of stomata and increased pro-
duction of compatible osmoprotectants and antioxidants.
Limitations in photosynthesis and changes in redox status of the mi-
tochondrion promote increased production of ROS and downstream sig-
naling pathways. More than half of the known drought-responsive genes
show also induced gene expression by salt stress. This includes ABA re-
sponsive pathways, which are active under both types of stress indicating
significant signalingcross-talk (Shinozaki et al., 2003).
Tolerance to the resulting secondary oxidative stress of salt stress is
apparently highly important for stress tolerance: thus, a number of salt tol-
erant species increase the activity of antioxidant enzymes and accumulate
antioxidants in response to salt stress, while salt-sensitive species fail to
do so. Biotech tools can therefore be used to selectively express the anti
oxidant enzymes to mitigate the stress induced by high salt concentrations.
13.5.7 TEMPERATURE STRESS
Ornamental plant species perform best only in a characteristic temperature
range, which depending on the species might be very narrow. Extremely
high or low temperatures affect vital cell functions such as enzyme activ-
ity, cell division and membrane integrity. Nevertheless, heat and cold ac-
climation is possible, as mild stress pretreatment can significantly enhance
the thermo-tolerance of plants (Thomashow, 1999).
