The features of root formation of some fodder semi-shrub and shrub halophytes in the foothill desert of Uzbekistan

Distinguishing feature of halophytes as fodder plants are high nutritional value, stable balance of nutrients over seasons, especially during critical periods of pasturing during autumn and winter, and a high content of essential amino acids. Halophytic fodder dwarf semi-shrubs, Kochia prostrata (L.) Schrad. and Salsola orientalis S.G. Gmel., and shrubs, Haloxylon aphyllum (Minkw.) Iljin and Aellenia subaphylla (С.А. Меу) Aellen. perform high and sustainable fodder productivity under xerothermic conditions of the Central Asian deserts. In these conditions, shrub and semi-shrub halophytes can successfully complete a full life cycle due to structural, physiological and biological adaptations. These re a succulent type of the leaf photosynthetic apparatus (R.M. Ogburn et al., 2010), a multilayer epidermis, thickening of the cuticle (R.F. Sage et al., 2011) and the C4 plants which are more efficient in transpiration compared to C3 plants and lower water consumption (V.I. Pjankov et al., 1991; V.I. Pankov, 1993). Roots play a central role in the yield formation and now considered key drivers of the second "green revolution". Knowledge of the Chenopodiaceae shrubs’ and semi-shrubs’ root formation in the foothill desert conditions elucidates fundamental peculiarities of these halophytic plant biology and provides the correct placement of the crops in arid zones. We compared parameters of root formation in shrubby and semi-shrubby halophyte species to identify their ecological role in the conditions of the Central Asian foothill desert (Nishan steppe, Kashkadarya region, Republic of Uzbekistan, 2015-2020) in plants of the 1st and 5th year of life. The halophytes of Chenopodiaceae family have acquired adaptive properties and increased production functions due to evolutionary developed powerful and deeply penetrating roots capable of the use of precipitation, condensation moisture and shallow ground water. Semi-shrubs Kochia prostrata (L.) Schrad., Salsola orientalis S.G. Gmel. and shrubs Haloxylon aphyllum (Minkw.) Iljin, Aellenia subaphylla (С.А. Меу) Aellen. are capable of rapid root growth and development. The roots of 1-year old plants penetrate into the soil to a depth of 235 cm in H. apyllum , 150 cm in A. subaphylla , 200 cm in S. orientalis , and 215-295 cm in K. prostrata . At the age of 5 years, the roots reached a depth of 1240 cm, 600 cm, 550 cm, and 580 cm, respectively. Therefore, the root length exceeds the height of the aerial part in the 1st year by 4-4.5 times, and at the age of 5 years by 6 times. The ability to high growth rates of the root system is an important condition for uninterrupted water absorption by the roots in conditions of moisture deficiency and drought. The depth of penetration of the root system of plants of different life forms (shrubs, semi-shrubs) is strongly influenced by the water-physical properties of the edaphic environment. In conditions of permanent soil moisture deficiency, the root system tends to constantly go deeper into the soil-soil environment, breaking through dense, cemented soil layers. In our opinion, for semi-shrubby, shrubby halophytes can not only uptake water by roots from deep soil but also move it to drier soils horizons where this water can be used by plants with a shallow root system. Therefore, the studied halophytes can obviously provide a function of hydraulic lift.