Plant Drought Tolerance: Some Genetics and Agronomics Relevant Aspects for Breeding in Forage Species pp. 157-188
Authors: (Gerardo Tapia, Hernán Acuña, Luis Inostroza, Instituto de Investigaciones Agropecuarias, INIA, Chillán, Chile)
Abstract: The agronomic effects of drought on forage species and grassland are related with
productivity and pasture persistence. The water shortage produce a growth reduction
caused by decreased turgor at cellular level, changes in membrane fluidity and
composition, decrease of photosynthetic electron transport, changes in solute
concentration and metabolism in general. Plants have developed several mechanisms for
tolerate drought stress in additive action and synergy. They are the origin for
morphological adaptations, which will give place to a stable acclimation for drought
tolerance. In grasses, water stress produce decrease in leaf growth and the number of
tillers, in white clover result in a severe reduction in stolon elongation. The roots
architecture, mass and depth, for specie, in particular, can be determinant in its response
to water stress. Reduction of soil water availability in pastures also produces changes in
fertilizer use efficiency, nutritive value, incidence of pests and diseases, and grazing
Morphological modifications reduce water loss which are associated to changes in
leaf anatomy as presence of trichomes, decrease of leaf area or loss of any leaves, change
in position respect to radiation, increase of cuticle thickness and decrease of stomatal
density. Leaves can modify cuticle thickness or compositions thanks to a phenotypic
plasticity given for regulation of cutin pathway biosynthesis and transport of lipidic
component to a leaf surface.
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