Comparison of Osmotic Regulation in Dehydration- And Salinity-Stressed Sunflower Seedlings

Abstract

2 Plant dry matter accumulation rate (DMAR), relative water content (RWC), electrolyte leakage percentage (ELP), chlorophyll content, osmotic adjustment ability (OAA), and osmotica accumulation in leaves of sunflower (Helianthus annuus L.) seedlings under different levels of dehydration and salinity stress induced by iso-osmotic PEG (polyethylene glycol) or sodium chloride (NaCl) were evaluated. Plants were subjected to four stress treatments for 10 days: −0.44 MPa PEG6000, −0.44 MPa NaCl, −0.88 MPa PEG6000, −0.88 MPa NaCl. Results showed that PEG and NaCl treatments decreased the plant's DMAR and RWC, and NaCl treatments had more severe inhibitory effect on the plants than PEG treatments. Leaf ELP in sunflower seedlings increased after NaCl and PEG treatments. However, leaf ELP under salt stress was higher than that under dehydration stress (PEG treatment). All stress treatments increased OAA in plant leaves. Leaf OAA was enhanced significantly as PEG concentration increases, while leaf OAA was less enhanced at higher concentration of NaCl. OAA of sunflower leaves under dehydration stress was due to an increase in potassium (K + ), calcium (Ca 2+ ), amino acid, organic acid, magnesium (Mg 2+ ), and proline content. OAA of sunflower leaves under moderate salt stress was owing to an increase in K + , chlorine (Cl − ), amino acid, organic acid, sodium (Na + ), and proline content, and was mainly due to an accumulation of K + , Cl − , Na + , and proline under severe salt stress.

Physiological and Biochemical Responses of Ulva prolifera and Ulva linza to Cadmium Stress

“…After blotting dry with absorbent paper, seaweeds were dipped into liquid nitrogen for 20 min. The frozen seaweeds were thawed in a syringe for 50 min, and the seaweed sap was then collected by pressing the seaweed in the syringe [18]. The π 100 was measured by using a fully automatic freezing-point osmometer (8P, Shanghai, China).…”

Comparison of individual and combined effects of salinity and deficit irrigation on physiological, nutritional and ornamental aspects of tolerance in Callistemon laevis plants

“…Common responses in species exposed to saline or drought stress are an increase in osmotic adjustment and changes in the cell wall elasticity, which result in the turgor loss point being reached at a lower leaf water potential and at a lower relative water content (Navarro et al, 2008;Zheng et al, 2010;Suárez, 2011). In our conditions, callistemon plants submitted to water deficit stress alone (W) showed osmotic adjustment and significant decreases in elasticity as a tolerance mechanism to drought in order to maintain turgor, as demonstrated in several ornamental species Álvarez et al, 2009, Álvarez et al, 2011.…”

“…2007;Razzaghi et al, 2012). Drought and salt tolerance in plants may be explained by functional and structural adaptations, such as growth regulations, osmotic adjustment, regulation of stomatal conductance, changes in cell wall elasticity, mineral nutritional and hormone balance all of which may help alleviate the harmful effects of both stresses (Zheng et al, 2010, Suárez, 2011.…”

Plant Responses to Salt Stress: Adaptive Mechanisms

“…Common responses in species exposed to saline or drought stress are an increase in osmotic adjustment, changes in the cell wall elasticity, decrease in saturation weight/dry weight ratio and increase in the percentage of water apoplastic, which minimizes the saline effects by maintaining the foliar turgidity. According to Navarro et al [123], Zheng et al [164] and Suárez [165] osmotic and/or elasticity adjustment result in the turgor loss point being reached at a lower leaf water potential and at a lower relative water content. The degree of osmotic adjustment differs among plant species.…”