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CROP PHYSIOLOGY & METABOLISM

Sorghum and Salinity

I. Response of Growth, Water Relations, and Ion Accumulation to NaCl Salinity

^a Department of Botany, Faculty of Science, Maseno University, P.O. Private Bag, Maseno, Kenya
^b Department of Plant Physiology, University of Bayreuth, Universitätstraße 30, 95440, Bayreuth, Germany

^* Corresponding author (erwin.beck{at}uni-bayreuth.de)

Crops grown in salt affected soils may suffer from drought stress, ion toxicity, and mineral deficiency leading to reduced growth and productivity. The present study was conducted to determine how salinity affects growth, water relations, and accumulation of cations of nutritional importance in various organs of grain sorghum [Sorghum bicolor (L.) Moench]. Two Kenyan sorghum varieties, Serena and Seredo, were grown in a greenhouse in quartz sand supplied with a complete nutrient solution to which 0 (control), 50, 100, 150, 200, and 250 mM NaCl was added. The 250 mM NaCl treatment significantly reduced the relative shoot growth rates, measured 25 d after the start of salt application, by 75 and 73%, respectively, for Serena and Seredo, and stem dry weight by 75 and 53%. In a similar way, young leaves were affected, with leaf blades of both varieties being reduced by 67% while sheaths were reduced by 83 and 87% for Serena and Seredo, respectively. Leaf water potential, osmotic potential, leaf pressure potential, and relative water content significantly declined with increasing salt stress. Roots and stems accumulated substantial amounts of sodium, saturating at 150 mM external NaCl. Accumulation of K⁺ and Ca²⁺ in the roots, stems, and leaves was strongly inhibited by salinity. Magnesium concentration of the roots was minimally impaired but that of the stems and leaves was strongly affected. Leaves continuously accumulated sodium, which was preferentially deposited in the sheaths. Mature leaves contained more Ca²⁺ and Mg²⁺ than young ones. The two sorghum varieties appear to sequester Na⁺ predominantly in roots, stems, leaf sheaths, and older leaf blades sparing the growing tissues as a salt tolerance mechanism. Nevertheless, greatly reduced concentrations of Ca²⁺, K⁺, and Mg²⁺ in leaves under salinity could cause cation deficiency which reduces plant growth.

Abbreviations: ANOVA, analysis of variance • DASA, days after start of salt application • RSGR, relative shoot growth rate • RWC, relative water content

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THIS ISSUE IN CROP SCIENCE

Crop Science 2004 44: 707-710. [Full Text]  

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