Proline Accumulation In Plants Of Different Ecological Groups As A Response To Water Deficit
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The diurnal changes in proline content were investigated in different plants including a desert shrub (Retama raetam), a halophytic grass (Spombolus virgimcus) and a cultivated crop (Zea mays). Though these species have different values of accumulated proline, the diurnal march in all speries exhibited the same trend. Low proline contents were recorded before sunrise then increase considerably by the progress of the day and decrease to low levels after sunset. The curves showing the diurnal march of proline content are parallel to those of the water saturation deficit. Both curves are mirror images of those showing the water content. The irrigation regime has a prominent effect on the proline content of Zea plants. Proline accumulation in water-stressed plants is reversed when the stress situation is eliminated by re-watering the plants. Continuous water supply to Retama cut branches results in a notable decrease of profile as compared to natural water-stressed plants. Stress due to salinity causes proline accumulation in Zea plants grown in saline soil. The proline content in Sporobolus exhibits seasonal variations comparable to those of the evaporative power of the atmosphere. The conditions of proline accumulation, which is a biochemical response of plants to environmental stresses, and the role of this accumulation are discussed.