Abiotic Stress Responses in Plants: Unraveling the Complexity of Genes and Networks to Survive - Abiotic Stress: Plant Responses and Applications in Agriculture - page 55

stress may vary significantly with the phenological stage of plants. Reproductive stages are
generally more sensible to stress than vegetative ones, but differences can also be made
between different phases of the reproductive stage. Mouhouche et al. [82] found in Phaseolus
vulgaris that periods of flowering were more sensitive than pod elongation and grain filling
phases. Casanovas et al. [83] reported a decrease of both leaf physiology and grain yield in
maize subjected to drought during flowering. Boonjung and Fukai [84] reported that when
drought occurred during vegetative stages, it had only a small effect on subsequent develop‐
ment and grain yield. The effect of water stress on yield was most severe when drought
occurred during panicle development.
Grapevine provides an interesting example of the complexity of the relationships between
drought stress and plant phenology. Traditionally, grapevine is a non-irrigated crop that
occupies extensive areas in dry lands and semi-arid regions [85]. Recently, in the Mediterra‐
nean region, irrigation was introduced to increase the low land yield. However, wine quality
is strongly dependent on the organoleptic characteristics of grapes which, in turn, particularly
in what concerns soluble sugar contents, are dependent on moderate drought stress during
berry expansion (i.e. in the phases from fruit set to veraison ). The irrigation strategy must
therefore maximize the vineyard production without decreasing berry quality, an objective
suitable for deficit irrigation programs (DRI).
Furthermore, a deep understanding of plant carbon assimilation and partitioning mechanisms
under different water regimes will be required in the frame of precision agriculture, as, in fact,
these mechanisms play a key role in the fine tuning of the balance between berry yield and
quality. Hopefully, this will lead to the adoption of criteria for irrigation scheduling based on
vine physiology [85].
3. Gene expression and regulation under abiotic stress
3.1. Complexity of gene expression and regulation
Plants have evolved intricate mechanisms at multiple levels that increase tolerance in order to
adapt to adverse conditions and to an ever sessile living. Plant growth and productivity are
affected to a great extent by environmental stresses such as drought, high salinity, and low
temperature. Expression of a variety of genes is induced by these stresses in various plants.
The products of these genes impact not only stress tolerance but also in stress response.
Genes induced during stress conditions function not only in protecting cells from stress
by producing important metabolic proteins, but also in regulating genes for signal trans‐
duction in the stress response. The first group includes proteins that probably function in
stress tolerance, such as chaperones or late embryogenesis abundant (LEA) proteins. The
second group contains protein factors involved in further regulation of signal transduc‐
tion and gene expression that probably function in stress response [86]. In some cases
networks and cascades of expression are activated in response to a stress condition. The
regulation of the expression of these networks is being studied during the last decades.