Drought, as an abiotic stress, is m

Drought, as an abiotic stress, is multidimensional in nature, and it affects plants at various
levels of their organization. In fact, under prolonged drought, many plants will dehydrate
and die. Water stress in plants reduces the plant-cell’s water potential and turgor, which
elevate the solutes’ concentrations in the cytosol and extracellular matrices. As a result, cell
enlargement decreases leading to growth inhibition and reproductive failure. This is
followed by accumulation of abscisic acid (ABA) and compatible osmolytes like proline,
which cause wilting. At this stage, overproduction of reactive oxygen species (ROS) and
formation of radical scavenging compounds such as ascorbate and glutathione further
aggravate the adverse influence. Drought not only affects plant water relations through the
reduction of water content, turgor and total water, it also affects stomatal closure, limits
gaseous exchange, reduces transpiration and arrests carbon assimilation (photosynthesis)
rates. Negative effects on mineral nutrition (uptake and transport of nutrients) and
metabolism leads to a decrease in the leaf area and alteration in assimilate partitioning
among the organs. Alteration in plant cell wall elasticity and disruption of homeostasis and
ion distribution in the cell has also been reported. Synthesis of new protein and mRNAs
associated with the drought response is another outcome of water stress on plants. Under
the water stress cell expansion slows down or ceases, and plant growth is retarded.
However, water stress influences cell enlargement more than cell division. Plant growth
under drought is influenced by altered photosynthesis, respiration, translocation, ion
uptake, carbohydrates, nutrient metabolism, and hormones.
3.1 Photosynthesis
Photosynthesis is particularly sensitive to the effects of water deficiency. Plants’ resistance to
water deficiency yields metabolic changes along with functional and structural
rearrangements of photosynthesizing apparatus. Photosynthesis of higher plants decreases
with the reduction in the relative water content (RWC) and leaf water potential. Lower
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