Jaromlr Lachman1, Milan Kroutil1 and Ladislav Kohout2

1Department of Chemistry, Faculty of Agrobiology, Food and Natural Resources,

University of Life Sciences in Prague, 2Department of Steroid Chemistry, Institute of Organic Chemistry and Biochemistry,

Academy of Sciences of the Czech Republic, Prague

Czech Republic

1. Introduction

Brassinosteroids (BRs) are plant natural polyhydroxysteroids supporting the plant growth; their structure resembles animal steroid hormones (Bajguz, 2010). In plants, steroid hormones serve as endogenous signaling molecules. Brassinosteroids act as positive growth regulators or as compounds responsible for plant stress tolerance. Phytoecdysteroids probably show an antifeedant activity (Kamlar et al., 2010). Brassinosteroids were classified as essential plant hormones nearly thirty years after the discovery of brassinolide (the first brassinosteroid) by Groove et al. (1979) in the rape (Brassica napus L.) pollen. Presence of brassinosteroids was demonstrated in many plant species including higher and lower plants and at the same time they were detected in parts of plants, e. g. pollen, seeds, leaves, stems, roots and flowers (Sakurai et al., 1999). Up to date it was characterized 70 compounds belonging to the class of brassinosteroids, among them 65 in free form and 5 conjugated (Zulo & Adam, 2002, Bajguz & Tretyn, 2003).

Brassinosteroids are phytohormones with pleiotropic effects. They influence growth, seed germination, cell elongation, photomorphogenesis and senescence (Upreti & Murti, 2004). In relation to the growth and growth regulators, the typical effect of brassinosteroids is coincidental elicitation of cell prolongation and division (Worley & Mitchell, 1971). Investigations confirm the ability of brassinosteroids quantitatively affect plant morphogenesis; this leads to the enhancement of number and growth productive lateral shoots and branches and thereby also to the enhancement of number of spikes, pods etc. (Sakurai et al., 1999). Brassinosteroids help to overcome stresses provoked by low and high temperature, drought, salt, infection, pesticides and heavy metals (Takematsu et al., 1986; Cutler, 1991; Kulaeva et al., 1991; Schilling et al., 1991; Hathout, 1996; Bajguz 2000; Anuradha & Rao, 2001; Krishna, 2003; Janeczko et al., 2005; Cao et al., 2005; Sharma & Bhardwaj, 2007 a, b; Kagale et al., 2007; Ali & Abdel-Fattah, 2006, Ali et al., 2007, 2008, Kroutil et al., 2010 a, b). Heavy metals give rise to antioxidant stress and brassinosteroids can

it effectively reduce and induce enhancing of antioxidants under heavy metal stress (Hayat et al., 2007a). In term of the affecting of the uptake of minerals after treatment with brassinosteroids an increase of the content of minerals in aerial plant biomass was demonstrated (Nafie & El-Khallal, 2000) as well as the BRs ability to decrease uptake of heavy metals and accumulation of radioactive elements (Cs, Sr) by plants (Bajguz, 2000; Khripach et al., 1999).

In term of the affecting of the uptake of minerals after treatment with brassinosteroids an increase of the content of minerals in aerial plant biomass was demonstrated (Nafie & El — Khallal, 2000). Brassinosteroids can affect quality of plant products. Treatment with brassinosteroids at anthesis increased the starch content in rice kernels (Fujii & Saka, 2001); at tillering it increased the content of fatty acids in barley ectoplasts and the change of their rate (Khripach et al., 1999).

The aim of this work was to evaluate the ability of brassinosteroids to affect the quality parameters of spring wheat grain: change of the content of minerals in grain and the yield increase of spring wheat cultivated in rational-intensity conditions after brassinosteroids treatment. Another goal of this study was to evaluate the ability of brassinosteroids to lessen the uptake and accumulation of heavy metals (Cd, Pb, Zn, Cu) in spring wheat plants cultivated on contaminated soil of a polluted burdened region in the Czech Republic. Content of heavy metals was investigated in biomass, grains and straw of treated and control plants.