Abstract
Salt impedes plant growth and yield. This study was conducted to explore the effect of plant growth stimulants (seaweed extract, humic acid) and potassium sulfate in alleviating salt stress in barley (Hordeum vulgare L.). Initially, 10 barley genotypes were germinated in a growth chamber at five salt levels (0, 0.5, 1.0, 1.5, and 2.0%). Increasing salt concentration reduced germination percent, the speed of germination, and seedling weight. One salt-tolerant genotype (Sharqiya Estate) and one salt-sensitive genotype (Red Sea) were selected and planted in greenhouse pots containing 2 kg of sand, then subjected to 10 and 15 dS m-1 salt levels using CaCl2.2H2O: NaCl (2:1) mixed with Hoagland solution. Four treatments consisting of (1) control (Hoagland solution), (2) seaweed extract at 4 Kg ha-1, (3) humic acid at 28 L ha-1, and (4) potassium sulfate at 300 Kg ha-1 were applied to each genotype under both salt levels. Seaweed extract resulted in higher shoot dry weight in the salt-sensitive genotype under both salt levels and maintained a low Na+/K+ ratio compared with humic acid and potassium sulfate. It also resulted in higher relative yield, relative water content, higher proline, and lower electrolyte leakage in the susceptible genotype at 10 dS m-1, but the result was not different from humic acid and potassium sulfate treatments at 15 dS m-1. Seaweed extract resulted in the highest catalase activity at 15 dS m-1 in both genotypes, with higher magnitude in the salt-tolerant genotype. These results suggest that seaweed extract has potential in improving barley growth under salt stress.
Highlights
0.9 million hectares of the irrigated areas in Egypt are affected by salinity (Doaa et al, 2012)
Application of seaweed extract resulted in the highest catalase activity at the 15 dS m-1 in both genotypes, with higher magnitude in the salt-tolerant genotype (Figure 1)
Application of seaweed extract, humic acid, and potassium sulfate under two salt levels (10 and 15 dS m-1) resulted in differential responses in shoot dry weight, number of tillers, root dry weight and root length between genotypes, with seaweed extract improving growth of the susceptible genotype under both salt levels, whereas potassium sulfate was most effective in the tolerant genotype
Summary
0.9 million hectares of the irrigated areas in Egypt are affected by salinity (Doaa et al, 2012). The majority of salt-affected areas are located in the northern-central part of the Nile Delta and on its eastern and western sides. Sixty percent of the cultivated land of the Northern Delta region, 20% of the Southern Delta and Middle Egyptian regions, and 25% of the Upper Egypt region are salt-affected (El-Banna et al, 2004). Salinity affects nearly 20% of the irrigated crop area (Munns & Tester, 2008), and the salt-affected area is expected to reach around 50% of the arable land worldwide in the near future (Mahajan & Tuteja, 2005). Relative to osmotic potential or the type of ions present in soil solution, plants exhibit different responses to salinity (Kiliç et al, 2008)
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