Participation of Plant Hormones in Growth Resumption of Wheat Shoots Following Short-Term NaCl Treatment

Abstract

The effects of sodium-chloride salinity on the leaf elongation rate, transpiration rate, cell sap osmolality, and phytohormone content in 7-day-old shoots of durum wheat ( Triticum durum L.) were studied. Leaf growth was suppressed under the salinity stress and resumed 1 h after NaCl removal. The resumption of leaf growth coincided with a decrease in the transpiration rate due to the rapid ABA accumulation in the differentiation leaf zone. The increased IAA concentration in the growing leaf zone promoted the formation of the attraction signal. The authors concluded that the changes in phytohormonal status in wheat plants occurred already following short-term (up to 1 h) salinity and were directed to the maintenance of plant growth under these conditions.Abbreviations : PhT-physiological solution containing 0.05% Tween-20; RWC-relative water content.

Effects of short- and long-term salinity on leaf water relations, gas exchange, and growth in Ipomoea pes-caprae

“…The time required for osmotic adjustment would be important for surviving the salinity shock and, thus, the ability to alter plant water potential components on a short-term basis may be especially relevant in coastal and salt marsh environments where rapid fluctuations in salinity occur (Bowman and Strain, 1988). Fast osmotic adjustment depends on the delivery rate of solutes exported from roots or on the synthesis of organic solutes (Akhiyarova et al, 2005;Else et al, 1994;Flowers et al, 1986;Lacerda et al, 2003). Then, in I. pes-caprae a limited ion delivery at short-term and/or a low synthesis of organic solutes during the initial period of stress may explain the delay in osmotic adjustment at high salinity.…”

“…These probably include rapid osmotic adjustment and recovery of photosynthetic capacity following tidal inundation (Akhiyarova et al, 2005;Bowman and Strain, 1988;Flowers et al, 1986). In some salt marsh and crop species, this adjustment to seawater salinity can be achieved in 24-48 h (Akhiyarova et al, 2005;Bowman and Strain, 1988;Flowers et al, 1986;McNulty, 1985;Murphy et al, 2003).…”

“…These probably include rapid osmotic adjustment and recovery of photosynthetic capacity following tidal inundation (Akhiyarova et al, 2005;Bowman and Strain, 1988;Flowers et al, 1986). In some salt marsh and crop species, this adjustment to seawater salinity can be achieved in 24-48 h (Akhiyarova et al, 2005;Bowman and Strain, 1988;Flowers et al, 1986;McNulty, 1985;Murphy et al, 2003). Fast osmotic adjustments require ion accumulation up to a concentration equal to or greater than that of the surrounding root solution in order to achieve an osmotic gradient for the uptake of soil water (Flowers et al, 1986;Greenway and Munns, 1980;Naidoo and Rughunanan, 1990).…”

“…Additionally, a decrease in stomatal conductance and transpiration rate is likely to be the first plant defence against increases in soil salinity (Gale and Poljakoff-Mayber, 1970;Gul et al, 2001;Redondo-Gómez et al, 2007;Robinson et al, 1997). Leaf gas exchange is generally reduced when soil salinity increases rapidly as a consequence of a reduction in stomatal conductance, but in the long-term some metabolic determinants of photosynthesis may also be inhibited (Akhiyarova et al, 2005;Flowers et al, 1986;Redondo-Gómez et al, 2007;Seemann and Critchley, 1985). Salinity also may affect plant growth.…”

“…Salinity also may affect plant growth. At short-term, growth inhibition can be explained by reduced leaf elongation through decrease in turgor of cell expanding tissues, while at long-term salinity affects many different aspects of growth, including those associated with water stress and those specific to NaCl (Akhiyarova et al, 2005;Greenway and Munns, 1980;Munns and Termaat, 1986;Ramani et al, 2006;Thiel et al, 1988). Thus, when salinity tolerance and physiological responses are evaluated in species that have evolved under naturally occurring salinity stress, both the intensity and the time course over which the stress is imposed should be considered (Bowman and Strain, 1988;Flowers et al, 1986;Howard and Mendelssohn, 1999).…”