It is important to determine if the toxic effects of Naþ,or the osmotic potential of NaCl, or the combination ofboth, are the causes for salinity stress in plant. A newand interesting finding by Genc et al. [62] has determined the importance of Naþ toxicity and NaClosmotic potential for wheat growth under salinitystress. They distinguished between the effects of Naþtoxicity and NaCl salinity and found that Naþ exclusionfrom the leaf is an important mechanism diminishingthe toxic effects of Naþ on wheat growth. However, theimportant mechanism determining salinity tolerance inwheat is osmoregulation. Accordingly, rather thanenhancing wheat tolerance to Naþ toxicity, breedingefforts must be directed toward improving wheat toleranceto NaCl salinity stress.The analysis of 75 metabolites, including aminoacids, organic acids, sugars, and polyols, indicated thatthe alteration of metabolite production was differentunder alkali and salt stress, as alkali stress was moredamaging to the production and accumulation ofmetabolites. Under salt stress, the production of sugarresulted in the adjustment of the osmotic potential.Alkali stress at high pH negatively affected: (1) the rateof photosynthesis, (2) the production of sugars andamino acids, and (3) the metabolism of N, and (4) it alsoinhibited glycolysis. However, the authors indicatedthat Ca2þ had a significant effect on wheat toleranceunder alkali stress and resulted in the exclusion ofNaþ [46].
It is important to determine if the toxic effects of Naþ,<br>or the osmotic potential of NaCl, or the combination of<br>both, are the causes for salinity stress in plant. A new<br>and interesting finding by Genc et al. [62] has determined the importance of Naþ toxicity and NaCl<br>osmotic potential for wheat growth under salinity<br>stress. They distinguished between the effects of Naþ<br>toxicity and NaCl salinity and found that Naþ exclusion<br>from the leaf is an important mechanism diminishing<br>the toxic effects of Naþ on wheat growth. However, the<br>important mechanism determining salinity tolerance in<br>wheat is osmoregulation. Accordingly, rather than<br>enhancing wheat tolerance to Naþ toxicity, breeding<br>efforts must be directed toward improving wheat tolerance<br>to NaCl salinity stress.<br>The analysis of 75 metabolites, including amino<br>acids, organic acids, sugars, and polyols, indicated that<br>the alteration of metabolite production was different<br>under alkali and salt stress, as alkali stress was more<br>damaging to the production and accumulation of<br>metabolites. Under salt stress, the production of sugar<br>resulted in the adjustment of the osmotic potential.<br>Alkali stress at high pH negatively affected: (1) the rate<br>of photosynthesis, (2) the production of sugars and<br>amino acids, and (3) the metabolism of N, and (4) it also<br>inhibited glycolysis. However, the authors indicated<br>that Ca2þ had a significant effect on wheat tolerance<br>under alkali stress and resulted in the exclusion of<br>Naþ [46].
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