Effect of nickel on growth, proliferation, and differentiation of root cells in Triticum aestivum seedlings

Abstract

The effect of 10 -6 and 10 -4 M NiSO 4 on cell growth, proliferation, and differentiation was studied over 48 h in seminal and lateral roots of five-day-old Triticum aestivum seedlings. 10 -6 M NiSO 4 did not significantly affect the root system, whereas 10 -4 M NiSO 4 inhibited its development. However, 10 -6 M NiSO 4 disturbed the contacts between the groups of closely related cells of the rhizodermis in the meristem. In the exodermis, an additional layer of cells was formed. At the nickel concentration of 10 -4 M, cell divisions in the outer layers of the root cells and metaxylem ceased earlier than in other root tissues positioned both centripetally and acropetally. Differentiation of protophloem sieve elements was completed in the meristem but at a greater distance from the root tip. Cell elongation started at the same distance from the root tip as in control plants. The rate of elongation decreased, and acropetally it stopped. Therefore, the cells of the xylem and metaphloem started to differentiate, and primordia of lateral roots were initiated and formed closer to the root tip. At a lethal concentration ( 10 -4 M), nickel induced necroses of elongating cells of the endodermis and pericycle. Nickel is supposed to enter the tissues of the central cylinder predominantly via the protoxylem and rapidly translocate along the xylem. As a result, the incubation of the roots at this concentration for 48 h almost did not affect the development of the phloem and probably sugar unloading, that makes possible to maintain the growth of meristematic cells and the cell division of the most important tissues for longer time.

Oxidative stress and fluctuations of free and conjugated polyamines in the halophyte Mesembryanthemum crystallinum L. under NaCl salinity

“…Our previous study showed that exposure of wheat seedlings to Ni led to an increase in root lignin content (Gajewska et al 2005). It can be suggested that a reduction in root growth in wheat exposed to excess Ni concentration might be associated with both decline in mitotic activity and restriction of cell elongation, which is in agreement with the recent findings of Demchenko et al (2005).…”

Essential Roles and Hazardous Effects of Nickel in Plants

“…Proposals for causative mechanisms include (1) a general metabolic disorder (Mishra and Kar 1974;Baccouch et al 1998a;Murch et al 2003), (2) a decrease in cell wall plasticity (Pandolfini et al 1992), (3) impaired cell division and elongation (Robertson and Meakin 1980;Demchenko et al 2005), (4) disorganization of nuclear structures (Sresty and Rao 1999), (5) chromosomal aberrations (Liu et al 1995), and/or nutritional imbalances ). The injury produced by treatment with 1.5-5.00 mM NiCl 2 caused mitotic tip arrest of Vicia faba roots.…”

Nickel in the Environment and Its Role in the Metabolism of Plants and Cyanobacteria

“…Pandolfi ni et al [115] measured root lipid peroxidation already at 20 µM Ni 2ϩ in Triticum. Demchenko et al [116] observed inhibition of root development only at 100 µM Ni 2ϩ , when cell elongation decreased and later cell division stopped. But 1 µM Ni 2ϩ in the same experiment already led to subtle changes in the morphology of the rhizodermis, the relevance of which remained unclear.…”