A tabayeva S.D., Nurmahanova A.S., Asrandina S.S., Alybayeva R.A., Kenzhebayeva S.S. Plants under the combined effect of salinity and heavy metals

1Al-Farabi Kazakh national university, Research Institute of Ecology Problems, Almaty, Kazakhstan *Е-mail: sauleat@yandex.ru

Аннотация

Large areasof soil and water, particularly in the vicinity of largecities and large industrial complexes
are contaminated with heavy metals. Another environmental problem is a salinity. The main threat to
water resources in many countries is irrigated agriculture. Saline ground water accelerate salinization
of soils. Salinization of ground water as desertification factor has two major aspects: the growth of salt
marsh deserts in drainage basins and salinization of irrigated lands. The proportion of saline soils is about
20% of the entire area of irrigated arable land. The result is the combined effect of salinity and heavy
metals on the ecosystems. In these areas, agriculture is developing, and there are located wheat, barley
and other crops. Heavy metals and salinity cause changes in the physiological, biochemical processes
due to accumulation of toxic ions in plant parts. In the review are presented data on the effect of heavy
metals and salinity on plant growth and biomass accumulation, effect of different concentrations of
heavy metals like cadmium, nickel, sinc, copper and sodium chloride on plants growth. The joint effect
of salinity and heavy metals is expressed in a change of anatomical parameters of leaves as a reduction
in the thickness of the upper and lower epidermis, reducing the diameter of the conductive beams as an
adaptive response to the flow of ions and salts of heavy metals. Change the anatomical parameters of
plants roots under the combined effect of salinity and heavy metals is expressed in increasing exoderm
thickness, providing a peripheral barrier to the penetration of toxic ions in the apoplast. An anatomical
indicator that affect the level of the whole organism - the diameter of the vascular bundles, the ratio
exoderm thickness to the thickness of the endoderm, the diameter of the central cylinder can be used
as a test for the resistance of plants to heavy metals and salinity. Under the combined effect of salinity
and heavy metal the physiological and biochemical parameters such as growth and accumulation of
biomass, relative water content, content of photosynthetic pigments are reduced and the level of lipid
peroxidation as an oxidative stress index is increased. In response to salinity and heavy metals the activity

of antioxidant enzymes, polyamines, stressful amino acids as integral indicators of plant resistance
are increased. The combined effect of heavy metals and salinity aggravates the separate effect of both
stressors by increasing osmotic stress, as a result of the high level of dehydration (RWC) and the toxic
effect of salinity (NaCl) and heavy metals ions.