Analysis of the impact of soil pollution with heavy metals on the ontogenesis of oil crops in arid conditions (using

This paper presents the results of a study examining the combined effects of drought and increasing concentrations of the most common agricultural soil pollutants - cadmium (Cd) and lead (Pb) - on the vegetation of Helianthus annuus L. Phenological observations were conducted regularly in a field experiment throughout the entire vegetative development period and focused on recording the main phenophases, from seedling emergence to head maturation. A delay in seedling emergence was observed in soils contaminated with heavy metals and with a soil moisture deficit, as well as an increase in the sunflower vegetation period under the influence of Cd and a reduction under the influence of Pb, primarily due to an extension/shortening of the flowering and seed filling periods, respectively. It was established that the biological minimum temperatures required to initiate a certain phenophase under Pb soil contamination do not differ from the control, while under the influence of Cd, the opposite trend was revealed: the heat requirement of plants increases dose-dependently. Increased dose-dependent accumulation of Cd in sunflower seeds was established.