Plasticity in sunflower leaf and cell growth under high salinity

Abstract

A group of sunflower lines that exhibit a range of leaf Na(+) concentrations under high salinity was used to explore whether the responses to the osmotic and ionic components of salinity can be distinguished in leaf expansion kinetics analysis. It was expected that at the initial stages of the salt treatment, leaf expansion kinetics changes would be dominated by responses to the osmotic component of salinity, and that later on, ion inclusion would impose further kinetics changes. It was also expected that differential leaf Na(+) accumulation would be reflected in specific changes in cell division and expansion rates. Plants of four sunflower lines were gradually treated with a relatively high (130 mm NaCl) salt treatment. Leaf expansion kinetics curves were compared in leaves that were formed before, during and after the initiation of the salt treatment. Leaf areas were smaller in salt-treated plants, but the analysis of growth curves did not reveal differences that could be attributed to differential Na(+) accumulation, since similar changes in leaf expansion kinetics were observed in lines with different magnitudes of salt accumulation. Nevertheless, in a high leaf Na(+) -including line, cell divisions were affected earlier, resulting in leaves with proportionally fewer cells than in a Na(+) -excluding line. A distinct change in leaf epidermal pavement shape caused by salinity is reported for the first time. Mature pavement cells in leaves of control plants exhibited typical lobed, jigsaw-puzzle shape, whereas in treated plants, they tended to retain closer-to-circular shapes and a lower number of lobes.

Leaf sodium accumulation facilitates salt stress adaptation and preserves photosystem functionality in salt stressed Ocimum basilicum

“…6), it is conceivable that the reduction of leaf area and shoot fresh weight at this stage was mainly caused by the reduction of cell elongation and division (osmotic phase of stress adaptation) (Munns and Tester, 2008). In a study comparing sunflower lines with different ability in ion transport and compartmentation (Céccoli et al, 2015), it was shown that early stage accumulators (see 100 mM NaCl stressed GEN plants at 13 DAST, Fig. 6) presented impaired cell division, which resulted in leaves with reduced cell number than in a Na + -excluding line.…”

Vigour/tolerance trade‐off in cultivated sunflower (Helianthus annuus) response to salinity stress is linked to leaf elemental composition

“…Compared to other crop species, cultivated sunflower has been shown to be moderately salt tolerant (Katerji, van Hoorn, Hamdy, & Mastrorilli, ), as has safflower, a closely related crop species (Yeilaghi, Arzani, & Ghaderian, ). Additionally, cultivated sunflower shows genotypic variation in response to abiotic stresses, including drought (e.g., Ahmad, Ahmad, Ashraf, Ashraf, Waraich, ), nutrients (e.g., Cechin & de Fatimas Fumis, ) and salinity (e.g., Ceccoli et al, ; Katerji et al, ; Rawson & Munns, ; Shi & Sheng, ). Given the moderate salt tolerance and putative genotypic variation in response to salinity in sunflower, there is a potential for identifying a range of salinity tolerances in cultivated sunflower genotypes that could be linked to physiological mechanisms underlying salt tolerance given a broad set of genotypes.…”

Stress Induces Trait Variability across Multiple Spatial Scales in the Arid Annual Plant Anastatica hierochuntica

“…Plastic response to salinity was found to affect leaves by increasing respiration and reducing leaf area and limiting cell division, which generally limit growth, e.g., Refs. [ 44 , 45 ], but may also result in more leaves [ 46 ]. Together, the results further support the conclusion that A. hierochuntica relies on plastic responses in relation to harsh conditions.…”