Salinity effects on leaf ion composition and salt secretion rate in Avicennia germinans (L.) L.

Abstract

The effect of salinity on leaf water relations, and rate and ionic composition of leaf secretion was investigated in plants of Avicennia germinans growing under controlled salinity conditions. Increases in salinity from 0 to 940 mol NaCl m -3 reduced the predawn water potential from -0.56 to -4.16 MPa and the solute potential from -2.27 to -4.48 MPa, whereas the pressure potential remained positive in all treatments. Compared to the control, at 940 mol NaCl m -3 Na + and Cl -concentrations of leaf sap increased 19 and 7 times, respectively. With the addition of salt the main ions accumulated in leaves were Na + and Cl -whereas plants grown without salt accumulated K + in leaves at levels similar to those of Na + with salt treatments. Secretion rates of Na + and Cl -ions increased up to the highest salinity treatment, amounting to 59 and 46 times respectively, compared to control plants. The increase in secretion rate contributed to counteract the increase of salt concentration in the leaf. In the treatments receiving salts, the Na + /K + ratio of leaf sap ranged from 4 to 10, whereas that of the secretion ranged from 24 to 56. The ratio of Cl -vs the rest of anions remained around 3 in the leaf sap of salt-treated plants whereas it varied between 96 and 243 in the secretion. With increasing salinity higher secretion rates maintained the internal ion leaf concentration relatively low. The selective character of the secretion contributes to maintain favourable Na + /K + and Cl -/anion ratios in the leaf cells.

NaCl salinity-induced changes in water status, ion contents and photosynthetic properties of Shepherdia argentea (Pursh) Nutt. seedlings

“…Different letters in the same column are significantly different at P < 0.05 level, as determined by DMRT sary for maintaining the turgor pressure (Navarro et al 2003). Through the analysis of water relations in the leaves of S. argentea, we observed that plants adjusted their Ψ w to more negative levels as salinity increased (Figure 1), which is a common reaction to salinity similar to those reported for other species (Navarro et al 2003, Suárez andMedina 2008). Significant reduction of RWC in leaves of plants treated with 400 and 600 mmol/l (Figure 1) indicated that salinity also resulted in dehydration at cellular level and dehydration symptoms were greater in higher NaCl concentration treatment because of the increasing cellular water loss.…”

“…The main negative effects of high salinity that influence plant growth and development are photosynthesis inhibition (Sharma et al 2005), water deficit (Suárez and Medina 2008), ion toxicity associated with excessive Cl -and Na + (Afzal et al 2008, Patel andPandey 2008), interference with nutrition leading to nutrient imbalance (Misra et al 1997). Bastías et al (2004) have reported that high concentrations of salt disrupt homeostasis in water relations and change the ion distribution at both cellular and whole plant levels.…”

Cell water content and lignification in maize regulated by rhizobacteria under salinity

“…Decreasing external water potential produces a net accumulation of solutes in cells, which lowers the cell osmotic potential necessary for maintaining the turgor pressure (Suárez and Medina, 2008). An interesting observation of this study was that plants inoculated with PGPR in normal as well as under salinity have greater RWC and cell membrane stability which is accordance with Sandhya et al (2010).…”

Improving Silvofishery Management Through Seedling Growth – Environment Quality Dynamic Relation Analysis

“…Further effect of salinity stress was explained by Kanai et al (2014) which showed a decreasing growth rate of mangrove under salinity stress. High salinity decreased the leaf half-life of mangrove (Suárez & Medina, 2008). Thus, it can be concluded that mangrove which grows in the saline environment has a lower growth rate compared to mangroves in the less saline environment.…”