IMPACT OF DIFFERENT CONCENTRATIONS OF PB WITH OR WITHOUT SALINITY ON THE GROWTH AND NUTRIENT UPTAKES OF DATE PALM PHOENIX DACTYLIFERA L. SEEDLINGKhairullah M. Awad, Mohammed A. Al-Najjar, Haleemah J. Al-Aradi, Mohammed H. Abass and Abdulzahra Alhello
Date palm seedlings were exposed to Pb (100, 300 and 600 mg.kg) alone or in combination with salinity (200 mM NaCl solution). The influences of Pb stress individually or combined with salinity stress on growth was examined based on number and length of the roots and leaves of date palm seedlings. Plant appearance was also observed. H2O2, Malondialdehyde (MDA) and Electrolyte leakage (EL) levels were estimated as oxidative stress markers. Macronutrients (NPK) and micronutrients (Zn, Fe and Cu) as well as Pb accumulation in the root and leaves were estimated. Results showed that 300 and 600 mg.kg-1 Pb inhibited the growth of date palm seedlings by reducing the length of the roots and leaves. A higher degree of reduction was detected in the treatment combining Pb and salinity. The interaction of Pb with salinity increased the contents of H2O2, MDA, and electrolyte leakage, which are oxidative stress markers in the root and leaves. The increase was more pronounced when 600 mg.kg-1 Pb was applied with salinity. The N and K contents in the treated date palm seedlings decreased with increasing Pb concentration, especially when the treatment was combined with salinity. By contrast, the P content increased. The contents of Fe and Cu decreased when the seedlings exposed to Pb. This effect was more evident when Pb stress was interacted with salinity. An opposite trend was observed for Zn content. Compared with the control, 600 mg.kg-1 Pb increased the Pb accumulation in the roots by 6.43 times and by 7.31 times when combined with salinity. Meanwhile, the Pb accumulation in the leaves increased by 9.91 when Pb stress was applied alone and by 10.88 when Pb was combined with salinity. The main finding of the work: The high level of Pb inhibited the growth of date palm seedlings by reducing the length of the roots and leaves. A higher degree of reduction was detected in the treatment combining Pb and salinity.